Agility and perturbation training for a physically active individual with knee osteoarthritis. (Case Report).

Knee osteoarthritis (OA) is a prevalent condition that contributes significantly to functional limitations and disability in older people. (1) Physical impairments associated with knee OA include pain, (2) loss of motion, (3) and decreased quadriceps femoris muscle strength. (3,4) These impairments are believed to contribute to physical disability and the progression of the disease. (5-7) Traditional exercise programs for people with knee OA have focused primarily on addressing limitations in lower-extremity muscle strength (force-generating capability), joint mobility, and aerobic capacity. (6,8,9) A recent meta-analysis of randomized clinical trials that tested interventions aimed at addressing these impairments demonstrated modest improvements in reduction of pain and self-report measures of function. (6) Although exercise therapy results in some benefit in reducing pain and improving function, these findings suggest that modification of traditional rehabilitation programs may improve the overall effectiveness of exercise therapy for people with knee OA.

We have observed in our clinic that patients with knee OA commonly complain of knee instability during activities of daily living. Specifically, they report episodes of "slippage" or "giving way" of their knees during activities such as walking, stair climbing, or standing from a sitting position. In some cases, patients stop participating in recreational activities because of the instability. The knee instability appears to be similar to that reported by younger individuals with knee ligament injuries. This observation led us to believe that incorporating training techniques that have been shown to be beneficial in improving knee stability for patients with ligament injuries might also be beneficial for patients with knee OA.

Recently, it was demonstrated that adding agility and balance training techniques to exercise therapy programs can enhance their effectiveness for people with knee instability associated with knee ligament injuries. (10-12) The agility training techniques included activities that emphasize quick starting and stopping movements, twisting movements, and quick changes in direction. The balance activities included perturbations of the individual's balance while standing on tilt boards and roller boards (perturbation training). The intent of agility and perturbation training activities is to expose people to activities that challenge knee stability and balance in a controlled manner during rehabilitation, a strategy that may allow them to develop motor skills adequate to protect the knee from potentially harmful loads during functional activities. Some evidence suggests that the addition of these techniques to rehabilitation programs for people with knee ligament injuries may return those individuals to higher levels of physical activity without recurrent episodes of knee instability. (10-12) On the basis of these findings, we hypothesized that similar training techniques might be beneficial for people who have knee OA and whose physical activities also are limited by knee instability.

It seems reasonable that perturbation and agility training techniques could be beneficial for patients with knee OA. Although many patients with knee OA may not be engaged in sports activities, many daily functional activities also expose the knee to twisting loads, sudden changes in direction of movement, sudden starts and stops, and challenges to balance. Agility and perturbation training might help patients with knee OA to develop motor skills adequate to protect their knees from potentially harmful loads while increasing their physical performance capabilities.

We believe that the same principles and techniques used in agility and perturbation training programs for young, active people with knee ligament injuries could be used to develop similar programs for patients with knee OA. The training techniques would need to be modified to reduce the intensity of effort and to prevent overloading of the knee in older individuals with knee OA. The purposes of this case report are to describe the development and implementation of a modified agility and perturbation training program that was used in conjunction with traditional rehabilitation activities and to report the treatment outcome for an individual with knee OA.

Considerations for Developing the Agility and Perturbation Training Program for People With Knee OA

When agility and perturbation training techniques are applied to patients with knee OA, the intensity of effort must be reduced to prevent overloading of knee joint structures, which might lead to pain, swelling, and inflammation. For agility training, this goal can be accomplished by changing the activities from running-based activities to walking-based activities. Vertical ground reaction forces are significantly lower during walking than during running (13); therefore, changing agility training techniques from running-based activities to walking-based activities should reduce the loads transmitted across the knee during training. Likewise, perturbation training techniques, which are typically performed with single limb support for sports rehabilitation programs, can be modified to incorporate double-limb support for patients with knee OA. Double-limb support techniques should reduce loading of the affected knee better than single limb support techniques; however, balance and knee stability still can be challenged by perturbations of support surfaces. The intensity of an agility and perturbation training program for patients with knee OA also can be reduced by decreasing the time or distances used for each training technique and by providing frequent rest periods between techniques during a training session.

The format of an agility and perturbation training program also needs to be considered. Schmidt (14) described elements that should be considered in the design of such training programs to ensure adequate carryover of learned skills to functional activity. These elements include the use of a variety of movement patterns and the use of variable practice methods. (14) The use of different movement patterns should be included to provide an opportunity for the individual to discover more effective patterns to solve movement problems. This concept was applied in the development of our program by use of a variety of balance and agility tasks, such as side stepping; crossover stepping; backward walking; practicing sudden starts, stops, and changes in direction during walking; and using multidirectional rotational and translational (sliding the support surface in a direction that is parallel to the ground) perturbations of support surfaces during balance training activities. Variable practice methods involve changing the sequence of tasks that will be practiced as well as having a patient practice a skill under various conditions, such as various speeds and degrees of difficulty. Variable practice is believed to enhance skill retention and to improve the learner's ability to solve novel movement problems. (14) We incorporated variable practice methods into our program by alternating the practice of agility and perturbation techniques from session to session and by instructing the patient to practice the training techniques at various speeds; by having the patient perform the walking activities around and over obstacles; and by using various speeds, directions, and magnitudes of platform displacements during the perturbation training techniques.

Case Description

History

The patient was a 73-year-old woman with a 2.5-year history of intermittent, bilateral medial knee pain, with the right knee being more painful than the left knee. She reported that when her knee pain was aggravated, the symptoms would gradually subside with activity modification. When she resumed her regular activity level, she occasionally experienced a recurrence of her knee pain. Despite her intermittent knee pain, she continued to play tennis and golf. Approximately 1 month before her initial physical therapy visit, she noted episodes of her knees giving way. She recalled no traumatic event that precipitated the episodes of giving way. She described the feeling that her knees "slipped" as she attempted to walk or participate in recreational activities. It was these episodes of instability that limited her functional activities and caused her to seek medical intervention. Radiographs revealed severe (grade IV, according to Kellgren and Lawrence (15)) osteoarthritic changes in the medial compartment of the right knee and moderate (grade III, according to Kellgren and Lawrence (15)) radiographic changes in the medial compartment of the left knee. She was subsequently referred by her physician for physical therapy evaluation and treatment with a diagnosis of bilateral knee OA.

The patient stated that before the onset of the episodes of giving way, she was able to walk 4.8 km (3 miles) daily, play tennis 3 times a week year round, and play golf 2 or 3 times per week, weather permitting, during the summer months. At the time of the initial physical therapy visit, she reported the inability to play tennis or golf as a result of the episodes of giving way. She also reported that she was unable to walk more than 3 to 5 city blocks without pain and giving way. She was unable to squat, had difficulty kneeling on the front of her knee, and was unable to negotiate stairs or rise from a chair without an increase in pain. The patient indicated that the location of pain during these activities was in the area of the medial tibiofemoral joint bilaterally. At the time of the initial examination, she reported that her pain was 5 out of 10 on a numeric pain scale (0="no pain" and 10="the most excruciating pain you have ever felt"). She stated that her knee pain increased to 8 out of 10 during increased physical activity, particularly when she attempted to play tennis.

The patient completed 2 self-report measures of physical function and disability, the Knee Outcome Survey--Activities of Daily Living Scale (ADLS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The ADLS is a knee-specific measure of physical function that assesses the effects of knee impairment on activities of daily living. (16-19) Psychometric testing has demonstrated ADLS scores to be reliable and valid for individuals with knee OA (internal consistency: correlation alpha coefficient=.92; concurrent validity: Pearson correlation with 36-Item Short-Form Health Survey [SF-36] score=.67). (18) The patient's ADLS score at her initial physical therapy visit was 62 out of a highest possible score of 100 (Tab. 1). Irrgang et al (16) reported that the average ADLS score before treatment for patients with a variety of knee disorders, including knee OA, was approximately 55 out of 100. Preliminary data from a study that we are currently conducting indicate that the average ADLS scores are approximately 62 out of 100 for people with knee OA (n=89, mean age [[+ or -] SD]=61 [+ or -] 9 years) and 98 out of 100 for people without knee OA or other knee pathology (n=27, mean age=57 [+ or -] 8 years). On the basis of these values, our patient's ADLS score was about average for people who have knee OA and who are seeking physical therapy intervention but lower than the ADLS score for people without knee OA or other knee pathology.

The WOMAC is a disease-specific, self-report health status measure that includes subscales for pain, stiffness, and physical function and that was developed for people with hip or knee OA. A total WOMAC score can be generated by summing the ratings for each subscale. The reliability and validity of WOMAC scores have been established. (20-22) For the WOMAC pain subscale, internal consistency was demonstrated by correlation alpha coefficients of .86 to .89, and test-retest reliability was demonstrated by a Kendall tau c statistic of .68. For the WOMAC stiffness subscale, internal consistency was demonstrated by correlation alpha coefficients of .90 to .91, and test-retest reliability was demonstrated by a Kendall tau c statistic of .48. For the WOMAC physical function subscale, internal consistency was demonstrated by a correlation alpha coefficient of .95, and test-retest reliability was demonstrated by a Kendall tau c statistic of .68. Construct validity, based on comparison of WOMAC subscale scores with Lequesne Index scores, was demonstrated by Pearson correlation coefficients of .57, .23, and .54 for the WOMAC pain, stiffness, and physical function subscales, respectively. Our patient's initial WOMAC scores were 7 out of 20 for pain, 3 out of 8 for stiffness, and 17 out of 68 for physical function, resulting in a total score of 27 out of 96 (Tab. 1). Lower WOMAC scores represent less pain and stiffness and less difficulty with physical function. Bellamy et al (20) reported average baseline scores for 57 patients with symptomatic OA of the hip and knee (mean age=66.5 years) as being 10 out of 20 for pain, 4 out of 8 for stiffness, and 32 out of 68 for physical function. Our preliminary data for individuals without knee OA or other knee pathology (n=27, mean age=57 [+ or -] 8 years) showed average WOMAC scores of 0.9 out of 20 for pain, 0.8 out of 8 for stiffness, and 1.3 out of 68 for physical function. These values indicate that our patient's WOMAC scores were better than average for patients with knee or hip OA but worse than those for individuals without knee OA or other knee pathology.

The patient reported that she had been taking 2 prescription medications before her course of physical therapy: Evista, * which was prescribed to increase bone density, and Celebrex, [dagger] a nonsteroidal anti-inflammatory medication. She continued to take these medications throughout her course of physical therapy. In addition, she also was taking glucosamine and vitamins E and D.

Examination

The patient's weight and height were 86 kg and 168 cm, respectively; thus, she had a body mass index of 30.5 kg/[m.sup.2]. The patient's right lower leg was in slight valgus relative to her femur; no other biomechanical abnormalities were observed. Passive and active knee extension were 2 degrees of hyperextension bilaterally. The patient was able to achieve 130 degrees of passive and active right knee flexion and 126 degrees of passive and active left knee flexion. Pain was not reproduced during passive and active knee motion testing. Manual muscle testing was performed and recorded in accordance with the muscle testing procedures described by Kendall et al. (23) The patient's quadriceps femoris muscle strength was rated Good bilaterally, and her hamstring muscle strength was rated Good for the right knee and Normal for the left knee. She did not complain of pain in either the muscle bellies or the tendons of the quadriceps femoris and hamstring muscles during resistance testing. Muscle length testing also was performed according to procedures described by Kendall et al. (23) Testing revealed bilateral shortening of the gastrocnemius and soleus muscles. No length restrictions were observed in the quadriceps femoris or hamstring muscle group.

During palpation, the patient said that tenderness was reproduced along the medial tibiofemoral joint lines bilaterally. Pain was not reproduced during palpation of the quadriceps femoris and hamstring muscle bellies or tendons, patellar tendon, patellar fat pad region, medial and lateral retinacular regions, patellofemoral region, or medial and lateral collateral ligaments. The patient had no visual or palpable signs of swelling or knee joint effusion and no evidence of increased skin temperature over any aspect of the patellofemoral or tibiofemoral joint.

Although the patient was able to walk up and down stairs, she reported that she had used a handrail since she had started to experience the episodes of instability and giving way. We attempted to evaluate her ability to negotiate a 10.2-cm (4-in) step without upper-extremity support, and she was unable to perform a single-leg step-down test on either leg, secondary to complaints of medial knee pain, weakness, and instability. The patient was able to complete the test with arm support from the therapist but still complained of medial knee joint pain. She did not complain of lateral knee or patellofemoral pain.

Varus and valgus stress testing, anterior and posterior drawer tests, and anterior and posterior Lachman tests were performed as described by Magee (24) to rule out the possibility of ligament injury, as the patient was reporting multiple episodes of giving way and instability. These tests did not reproduce the pain, and excessive joint laxity was not observed. Upon visual observation of the patient's gait on a level surface, she was noted to walk with flexed knees bilaterally during the stance phase of gait.

Intertester reliability for judgments based on the valgus stress test performed by physical therapists has been shown to be limited (laxity Kappa=.16, pain Kappa=.33, end-feel Kappa= .38). (25) To our knowledge, the reliability and validity of data obtained with the varus stress test have not been reported in the literature. Intratester and intertester reliability for judgments based on the Lachman test performed by physical therapists has been shown to be limited (intratester reliability Kappa=.44, intertester reliability Kappa=.69). (26) The predictive value of positive and negative Lachman tests performed by physical therapists were 44% and 64%, respectively. (26) The sensitivity and specificity for the anterior drawer test performed by orthopedic surgeons were reported as 76% and 86%, respectively. (27) The sensitivity and specificity for the posterior drawer test performed by orthopedic surgeons were reported as 90% and 99%, respectively. (27) We are unaware of any studies that have examined the specificity and sensitivity of these tests when performed by physical therapists.

The Get Up & Go Test, as described by Hurley et al, (25) was performed as a physical performance measure of function for balance and gait. To perform this test, the patient was seated on a standard-height chair with armrests. On the command "go," the patient stood up and walked along a level, unobstructed corridor as fast as possible. A stopwatch was used to measure the length of time it took for her to stand up and walk 15.2 m (50 ft). Hurley et al (28) did not report the reliability of measurements obtained with this test. The test-retest reliability of Get Up & Go Test measurements was examined in our clinic for 67 patients with knee OA, and the measurements demonstrated good reliability (intraclass correlation coefficient=.88; unpublished data). Our patient's initial Get Up & Go Test time was 10.06 seconds. Hurley et al (28) reported average Get Up & Go Test times of 16.5 seconds for subjects with knee OA (n=103, mean age=60.7 years) and 12.5 seconds for control subjects without OA (n=25, mean age=65 years). Average Get Up & Go Test times from our preliminary data were 11.3 seconds for subjects with knee OA (n=89, mean age=61 [+ or -] 9 years) and 8.1 seconds for subjects without knee OA (n=27, mean age=57 [+ or -] 8 years). On the basis of these values, our patient's Get Up & Go Test time was faster than average for people with knee OA.

On the basis of our examination findings, we believed that the patient's pain and instability during physical activity were related to her knee OA and not to some other acute extra-articular pathology. Her pain was limited to the medial compartment of her knees, and she did not complain of pain in other regions, such as the anterior knee, quadriceps femoris and hamstring muscle tendon insertions, patellar tendon or fat pad region, or collateral ligaments. We believed it unlikely that there was any acute pathology in the quadriceps femoris and hamstring muscles or tendons because we were unable to reproduce pain in these structures during passive and active motion testing of the knees or during resistance applied manually to the quadriceps femoris and hamstring muscles. There were no signs during palpation of knee swelling, effusion, or increased skin temperature that might have indicated the presence of acute synovitis or other inflammatory process of the knee.

We believed that our patient was a good candidate for the agility and perturbation training activities for a number of reasons. First, an important quality-of-life goal for the patient included returning to playing golf and tennis. To achieve this goal, we hypothesized that she would need to be able to perform many of the movement tasks that would be included in the agility and perturbation training program. Second, her complaint of knee instability during many activities of daily living, including walking, stair climbing, and standing from a sitting position, suggested to us that she was in need of activities that might promote the development of compensatory neuromuscular control mechanisms to maintain knee stability during functional tasks. Third, based on our examination, her overall levels of impairment and functional limitations were moderate in comparison with those of other patients with knee OA, and we therefore hypothesized that she would be likely to tolerate the agility and perturbation training program. Thus, we decided to incorporate agility and perturbation training techniques into her rehabilitation program.

Treatment

The patient participated in 12 treatment sessions at a frequency of 2 visits per week. During the patient's first 2 visits, the rehabilitation program consisted of therapeutic exercises performed in a heated pool and in the physical therapy gymnasium. The rationale for the pool exercises was to allow the patient to perform weight-bearing activities with less pain by reducing the load on the knees. The pool exercises included walking for 10 minutes in chest-deep water (progressing to 20 minutes in waist-deep water during the second treatment session), minisquats, toe raises, and four-way leg raises (in standing hip abduction, adduction, flexion, and extension) bilaterally in chest-deep water (progressing to waist-deep water). Braiding (lateral stepping combined with forward and backward crossover steps) and side stepping also were introduced in the pool, as was simulated pedaling while supported in a flotation device.

The patient denied any complaints of pain or discomfort following the first aqua therapy treatment. In addition, she reported that the exercises were only minimally challenging in the chest-deep water. As a result, the pool program was progressed to waist-deep water during her second visit. During this treatment, the patient noted increased difficulty with the exercises in the chest-deep water; however, she denied any complaints of pain or discomfort with the given pool exercises.

The patient's gymnasium program included therapeutic exercises to address impairment identified during the evaluation. The patient was given a non--weight-bearing calf stretch. The patient was seated with her legs extended in front of her, a strap was placed around the ball of the patient's foot, and she was instructed to pull her foot toward her until a gentle stretch was felt in the calf region. The stretch was held for 30 seconds and repeated 3 times on each side. The patient maintained the long-sit position for the isometric quadriceps femoris muscle contraction. A silver chloride electrode was placed on the quadriceps femoris muscle one handbreadth superior and medial to the superior border of the patella. The electrode was connected to a portable biofeedback unit. The patient was instructed to contract the quadriceps femoris muscle and hold the contraction for 6 seconds. She completed 20 repetitions of this exercise on each leg. The patient went on to perform a straight leg raise with the biofeedback unit. She was instructed to first contract her quadriceps femoris muscle and then lift the leg approximately 15 to 20 cm (6-8 in), maintaining the quadriceps femoris muscle contraction. She was instructed to lower the leg and relax the contraction once the leg reached the table. She was instructed to perform 20 repetitions on each leg. The patient also performed hamstring muscle curls on the table. She was positioned prone, and a 1.8-kg (4-lb) ankle weight was placed on each leg. The starting weight was based on a 10-repetition maximum (ie, the amount of weight a patient can perform a given exercise for 10 repetitions). The patient was instructed to bend her knee, bring her heel toward her buttocks, and repeat 10 times. Two sets of 10 repetitions were performed on each leg. In addition to the table exercises, the patient was placed on the seated leg press machine. The exercise was performed bilaterally with an initial weight of 31.8 kg (70 lb). Again, this weight was established based on a 10-repetition maximum, and the patient performed 2 sets of 10 repetitions. All of these strengthening exercises were progressed based on the patient's tolerance and response to current treatment. Finally, the patient was placed on the stationary bicycle for endurance training with a low level of resistance initially for 10 minutes and progressed based on the patient's tolerance and response.

After the first 2 visits, the patient was tolerating her exercise program well without complaints of discomfort during the exercises. She was tolerating weight-bearing activities in the pool without pain and indicated that the pool activities no longer seemed challenging. On her third visit, we decided to have the patient progress to performing the weight-bearing exercises out of the pool. The patient was able to perform the weight-bearing exercises and was able to walk approximately 60 m (200 ft) without complaint of pain. Because she appeared to tolerate the weight-bearing activities well, we decided to begin incorporating the agility and perturbation training techniques into the rehabilitation program.

General Description of the Agility and Perturbation Training Activities

The agility training techniques in the program included side stepping; braiding; front crossover steps during forward walking; back crossover steps during backward walking; shuttle walking (forward and backward walking to and from designated markers); and a multiple change-in-direction drill, in which the therapist provided hand signals at random to prompt the patient to change directions during walking (forward-backward, right-left lateral steps, diagonally backward-forward). The perturbation training consisted of 3 perturbation techniques. During the first technique, the patient stood on a 1.3-cm-thick (1/2-in-thick) foam surface with single-limb support while the therapist attempted to perturb the patient's balance in various directions. During the second technique, the patient stood with one foot on a stationary platform and the other foot on a roller board. The therapist applied translational (movement of the roller board parallel to the ground) perturbations to the roller board at random, with various directions and magnitudes of speed and displacement. During the roller-board perturbations, the patient was instructed to try to counter the therapist's perturbations by keeping the roller board in a stationary position. The patient was instructed not to overcome the therapist's perturbing force but rather to simply match the direction and magnitude of the force. Our intent with this technique was to encourage more selected responses from lower-extremity muscles to a destabilizing load rather than strong co-contraction responses to keep the knee stable. We acknowledge that we do not know whether we had this effect, as muscle activity was not measured during treatment. After 10 to 30 seconds of perturbations on each leg, the patient switched feet, and the technique was repeated. During the third technique, the patient stood on a tilt board with double-limb support, and the therapist applied anteroposterior and mediolateral perturbations to the tilt board in a random fashion.

Progression of the Agility and Perturbation Training Program

Table 2 provides a summary of the agility and perturbation training activities and the progression of training over the course of the patient's rehabilitation program. The table indicates that the patient did not perform all activities during each session. The agility techniques were alternated with the perturbation techniques from treatment session to treatment session. This was done to keep the intensity and duration of each session at a reasonable level for patient tolerance and because alternating movement experiences between sessions may improve long-term carryover of motor skills that may have been acquired during the training. (14) The average total treatment time per session was approximately 40 to 45 minutes, and the estimated time devoted to agility and perturbation training techniques was approximately 5 to 10 minutes per session. The therapist intermixed the agility and perturbation training techniques with other exercise activities and attempted to use different sequences of exercises from session to session. Altering the sequence of training activities from session to session may enhance the potential for long-term carryover. (14)

The difficulty level of the agility and perturbation training techniques was increased in a number of ways, as described in Table 2. Initially, the agility techniques were performed with hand-held assistance from the therapist. As the skill level of the patient improved, the hand-held assistance was replaced with standby supervision. The intensity of the agility training techniques was increased by increasing the number of activities and by increasing the distance that each technique was performed. Later in the rehabilitation program, an obstacle course was added. This included a series of cones, boxes, and dumbbells. The course began with 3 small dumbbells placed approximately 0.6 m (2 ft) apart. Next, 3 cones were placed approximately 1.2 to 1.5 m (4-5 ft) apart, and finally a 5.1-cm (2-in) box and a 15.2-cm (6-in) box were placed approximately 1.2 to 1.5 m apart at the end of the course. The patient was instructed to step over each of the dumbbells, walk to the right of the first cone, walk to the left of the second cone, and walk to the right of the third cone. The patient concluded the course by walking up and over the 5.1-cm box and then the 15.2-cm box. The perturbation training techniques also were increased from hand-held assistance to standby assistance as the patient's balance improved. For the roller-board technique, the activity initially was performed with the patient semiseated on the edge of the plinth and later was performed in the full standing position. Near the end of the rehabilitation program, catching and tossing a ball were added during the perturbation techniques.

The decision to increase the patient's activity level was based on her tolerance for the activities and her demonstration of improved skill with each session. She was monitored by the therapist before and after each treatment session for adverse signs and symptoms, such as increased pain, joint effusion, and increased skin temperature. The patient did not report pain or episodes of giving way at any time during performance of the agility and perturbation training techniques.

Home Program

The patient was given a home exercise program to supplement her supervised physical therapy program. The patient's program included the following walking-based activities: tandem ambulation, backward ambulation, side stepping, braiding, front crossover steps, and back crossover steps. The patient's husband attended therapy and was instructed in the proper technique for assistance and guiding if required by the patient. Only one of the perturbation techniques was simulated in the home exercise program. The patient was instructed to use a standard foam pillow to replicate the foam used in the clinic. She stood on the pillow with single-limb support while her husband attempted to perturb her balance in various direction. In addition to the coordination and agility training, the patient spent 20 to 30 minutes on the stationary bicycle 3 times a week.

Outcomes

At the time of the patient's fifth visit (2 sessions of the agility and perturbation training program), she stated that overall her pain was decreasing and she was experiencing less frequent episodes of giving way of the knee during walking and stair climbing. At the time of her seventh visit (fourth week) for physical therapy, she stated that she had gone to a local shopping mall for several hours without experiencing pain or knee instability while walking at the mall. She also reported that she had not experienced an episode of giving way of the knee during stair climbing or rising from a chair since the time of the fifth visit for physical therapy. On the ninth visit, after 4 weeks of physical therapy, the patient reported that she had played 9 holes of golf without knee pain or instability. She also had attempted to play tennis and had experienced some pain on lateral movements, which she rated as 3 out of 10 on a numeric pain scale.

Pretraining and posttraining outcome measurements are provided in Table 1. After completing 12 treatment sessions over 6 weeks, the patient no longer had pain with walking. She was able to go up and down stairs without the use of the handrail, and she had returned to playing golf without pain or knee instability. She reported that she still had decreased endurance, which now had become her primary limitation. She especially noted this after returning to playing tennis. She stated that she was able to walk 3.2 to 4.8 m (2-3 miles) without knee instability. During observation of the patient's gait on a level surface, the patient appeared to have adequate knee extension during the stance phase of gait without flexed knees. She was now able to perform a step-down test from a 10.2-cm (4-in) step without complaints of weakness or instability, an activity that could not be performed on initial evaluation.

Discussion

We believe that the patient in this case report is an example of a growing number of older people who would like to maintain a higher quality of life through active participation in physically challenging activities, despite the onset of age-related disease, such as OA. She had been an avid tennis player and golfer but had had to suspend these activities because of the pain and instability associated with her knee OA. Her single most important goal for rehabilitation was to restore her capacity to return to these recreational activities. In planning the treatment strategy for this patient, we determined that we would need to tailor the treatment program in a manner that would prepare her for coping with the physical demands placed on the lower extremities during participation in these recreational activities.

It would be inappropriate for us to conclude that our patient's favorable outcome was the result of the agility and perturbation training program. In addition to the agility and perturbation activities, the patient received standard exercises that addressed lower-extremity strength and joint mobility. However, we believe that the agility and perturbation training activities provided her with an opportunity to adapt to potentially destabilizing loads on the knee during rehabilitation, ultimately allowing her to return to her recreational activities. The agility and perturbation training program gave the patient additional exposure to pivoting, quick starting and stopping, and quick changes in direction and challenged her balance capabilities. The additional exposure to these activities may have allowed her to develop adequate motor skills for dealing with potentially destabilizing forces on the knee that may be encountered during recreational activities and activities of daily living.

Although our patient achieved a favorable outcome and tolerated the agility and perturbation training activities without difficulty, incorporating the general use of these activities into rehabilitation programs for other patients with knee OA should be approached with caution. It should be recognized that on the basis of our initial examination findings, we considered this patient to be only moderately affected by her condition in terms of physical impairments and level of disability. Patients who are more severely affected by the disease may have difficulty tolerating these activities. In such cases, therapists may need to initially focus their treatment plan on resolving pain and inflammation, muscle weakness, and limitations in joint mobility before patients can safely perform the agility and perturbation training techniques that we have described. We observed our patient's response to a general exercise program over the course of 2 treatment sessions before initiating the agility and perturbation training activities to ensure that she would be likely to tolerate these activities. In some cases, it may take longer for patients to be ready to tolerate these activities. We recommend continued monitoring of the patient for signs of recurring pain, inflammation, or episodes of instability once the agility and perturbation training program is initiated. If these symptoms occur, then the appropriateness of the activities for the patient should be reconsidered.

Supplementing rehabilitation programs for patients with knee OA with agility and perturbation training techniques may improve treatment effectiveness by allowing them to return to higher levels of activity in shorter time periods. Although it cannot be determined from this case report, we hypothesize that adding agility and perturbation training techniques might provide a way for patients to develop improved neuromuscular control mechanisms that would allow higher levels of functional performance than what might be achieved without the use of these activities. Future research efforts are needed to determine the role of agility and perturbation training in influencing neuromuscular control mechanisms and the outcome of rehabilitation in people with knee OA.

Table 1.
Pretraining and Posttraining Outcome Measurements (a)

Impairment and
Physical Performance
Measures                     Pretraining      Posttraining

Knee range of motion         Right: 2/0/130   Right: 5/0/130
  (hyperextension/neutral/   Left: 2/0/126    Left: 5/0/130
  flexion) ([degrees])

Manual muscle test           Right: Good      Right: Normal
  (quadriceps femoris        Left: Good       Left: Normal
  muscle)

Manual muscle test           Right: Good      Right: Normal
  (hamstring muscle)         Left: Normal     Left: Normal

Get Up & Go Test             10.06 s          9.10 s

Self-Report Measures         Pretraining      Posttraining
of Function

Numeric pain scale (0-10)    5: during
                                examination   2: during examination
                             8: worst pain
                                experienced   4: worst pain experienced
ADLS (0-100)                 62               90

WOMAC
  Pain subscale (0-20)        7                5
  Stiffness subscale (0-8)    3                3
  Physical Function          17               13
    subscale (0-68)

Total (0-96)                 27               21

(a) ADLS=Knee Outcome Survey-Activities of Daily Living Scale,
WOMAC=Western Ontario and McMaster Universities Osteoarthritis Index.
Table 2.
Summary of Agility and Perturbation Training Program Progression

Visit                                    Treatment
No.     Activities                       Intensity

 3      Front crossover steps
          during forward walking         6.1 m (20 ft) x 3 sets
        Back crossover steps
          during backward walking        6.1 m x 3 sets
        Side stepping -- moving
          right to left and then
          left to right                  6.1 m x 3 sets

 4      Single-leg standing on foam
          surface, with no               10 s x 3 sets
          perturbation of balance
        Roller-board perturbation        10 s x 3 sets

 5      Front crossover steps
          during forward walking         9.1 m (30 ft) x 3 sets
        Back crossover steps
          during backward walking        9.1 m x 3 sets
        Side stepping -- moving
          right to left and then
          left to right                  9.1 m x 3 sets
        Braiding -- alternating
          front and back crossover
          steps during side stepping     3.1 m (10 ft) in each
                                           direction x 3 sets

 6      Single-leg standing on foam
          surface, with no               20 s x 3 sets
          perturbation of balance
        Roller-board perturbation        20 s x 3 sets

 7      Front crossover steps during
          forward walking                9.1 m x 3 sets
        Back crossover steps during
          backward walking               9.1 m x 3 sets
        Side stepping -- moving
          right to left and then
          left to right                  9.1 m x 3 sets
        Braiding                         6.1 m x 3 sets
        Shuttle walking -- markers
          were placed at 1.5, 3.1, and   2 sets
          4.6 m (5, 10, and 15 ft);
          the patient walked forward
          to the marker and then
          backward to the start
          position for each of the
          3 markers, emphasizing quick
          changes in direction
        Multiple direction changes
          during walking -- the          20 s x 2 sets
          therapist directed the
          patient to walk forward,
          backward, sideways, or on a
          diagonal by cueing the
          patient with hand signals;
          changes in direction were
          cued randomly by the
          therapist

 8      Single-leg standing on foam
          surface, with perturbations    30 s x 3 sets
          of balance
        Roller-board perturbation        Progress to standing;
                                           10 s x 3 sets
        Tilt-board technique with
          double-limb support
          and anteroposterior and        10 s x 2 sets for
          mediolateral perturbations       each direction

 9      All activities listed in
          visit 7                        30 s x 3 sets; shuttle
                                           walking x 2 sets
        Initiate obstacle course         1 set
          walking -- figure-eight
          walking around cones placed
          3.1 m apart, stepping up
          onto and down off of a
          20.3-cm (8-in) box, and
          stepping over bolsters
          placed on the floor

10      Single-leg standing on foam
          surface,
          with perturbations             30 s x 3 sets
          of balance
        Roller-board perturbation        30 s x 3 sets
        Tilt-board technique with
          double-limb support
          and anteroposterior and
          mediolateral                   30 s x 2 sets in each
          perturbations                    direction

11      Front crossover steps
          during forward walking         15.2 m (50 ft) x 2 sets
        Back crossover steps
          during backward walking        15.2 m x 2 sets
        Side stepping -- moving right
          to left and then left
          to right                       15.2 m x 2 sets
        Braiding                         15.2 m x 2 sets
        Shuttle walking                  2 sets
        Multiple direction
          changes during walking         30 s x 2 sets
        Obstacle course                  1 set

12      Single-leg standing on foam
          surface, with perturbations    30 s x 3 sets
          of balance
        Roller-board perturbation        30 s x 3 sets
        Tilt-board technique with
          double-limb support and        30 s x 3 sets
          anteroposterior and
          mediolateral perturbations;
          ball tossing and catching

Visit
No.     Activities                       Level of Assistance

 3      Front crossover steps            Hand-held assistance
          during forward walking           from therapist for each
        Back crossover steps               activity
          during backward walking
        Side stepping -- moving
          right to left and then
          left to right

 4      Single-leg standing on foam      Hand-held assistance from
          surface, with no                 therapist
          perturbation of balance
        Roller-board perturbation        Patient semiseated on edge
                                           of plinth

 5      Front crossover steps            Hand-held assistance from
          during forward walking           therapist for each
        Back crossover steps               activity
          during backward walking
        Side stepping -- moving
          right to left and then
          left to right
        Braiding -- alternating
          front and back crossover
          steps during side stepping

 6      Single-leg standing on foam      No hand-held assistance;
          surface, with no                 progress to standby
          perturbation of balance          assistance
        Roller-board perturbation        Patient semiseated on edge
                                           of plinth

 7      Front crossover steps during     Standby assistance
          forward walking
        Back crossover steps during      Standby assistance
          backward walking
        Side stepping -- moving          Standby assistance
          right to left and then
          left to right
        Braiding                         Hand-held assistance
                                           from therapist
        Shuttle walking -- markers       Standby assistance
          were placed at 1.5, 3.1, and
          4.6 m (5, 10, and 15 ft);
          the patient walked forward
          to the marker and then
          backward to the start
          position for each of the
          3 markers, emphasizing quick
          changes in direction
        Multiple direction changes       Standby assistance
          during walking -- the
          therapist directed the
          patient to walk forward,
          backward, sideways, or on a
          diagonal by cueing the
          patient with hand signals;
          changes in direction were
          cued randomly by the
          therapist

 8      Single-leg standing on foam      Standby assistance for all
          surface, with perturbations      activities
          of balance
        Roller-board perturbation
        Tilt-board technique with
          double-limb support
          and anteroposterior and
          mediolateral perturbations

 9      All activities listed in         Standby assistance for all
          visit 7                          activities
        Initiate obstacle course
          walking -- figure-eight
          walking around cones placed
          3.1 m apart, stepping up
          onto and down off of a
          20.3-cm (8-in) box, and
          stepping over bolsters
          placed on the floor

10      Single-leg standing on foam      Standby assistance for all
          surface,                         activities
          with perturbations
          of balance
        Roller-board perturbation
        Tilt-board technique with
          double-limb support
          and in eachanteroposterior
          and mediolateral
          perturbations

11      Front crossover steps            Standby assistance for all
          during forward walking           activities
        Back crossover steps
          during backward walking
        Side stepping -- moving right
          to left and then left
          to right
        Braiding
        Shuttle walking
        Multiple direction
          changes during walking
        Obstacle course

12      Single-leg standing on foam      Standby assistance for all
          surface, with perturbations      activities
          of balance
        Roller-board perturbation
        Tilt-board technique with
          double-limb support and
          anteroposterior and
          mediolateral perturbations;
          ball tossing and catching

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the US Air Force or Department of Defense.

This article was submitted April 27, 2001, and was accepted October 14, 2001.

* Eli Lilly and Co, Lilly Corporate Center, Indianapolis, IN 46285.

[dagger] Pharmacia Corporation/Pfizer, 7000 Portage Rd, Kalamazoo, MI 49001.

References

(1) Guccione AA, Felson DT, Anderson JJ, et al. The effects of specific medical conditions on the functional limitations of elders in the Framingham Study. Am J Public Health. 1994;84:351-358.

(2) Creamer P, Lethbridge-Cejku M, Hochberg MC. Where does it hurt? Pain localization in osteoarthritis of the knee. Osteoarthritis Cartilage. 1998;6:318-323.

(3) Messier SP, Loeser RF, Hoover JL, et al. Osteoarthritis of the knee: effects on gait, strength, and flexibility. Arch Phys Med Rehabil. 1992;73: 29-36.

(4) Fisher NM, White SC, Yack HJ, et al. Muscle function and gait in patients with knee osteoarthritis before and after muscle rehabilitation. Disabil Rehabil. 1997;19:47-55.

(5) Rogind H, Bibow-Nielsen B, Jensen B, et al. The effects of a physical training program on patients with osteoarthritis of the knees. Arch Phys Med Rehabil. 1998;79:1421-1427.

(6) van Baar ME, Assendelft WJ, Dekker J, et al. Effectiveness of exercise therapy in patients with osteoarthritis of the hip or knee: a systematic review of randomized clinical trials. Arthritis Rheum. 1999;42: 1361-1369.

(7) Fisher NM, Pendergast DR, Gresham GE, Calkins E. Muscle rehabilitation: its effect on muscular and functional performance of patients with knee osteoarthritis. Arch Phys Med Rehabil. 1991;72:367-374.

(8) Hochberg MC, Airman RD, Brandt KD, et al. Guidelines for the medical management of osteoarthritis, part II: osteoarthritis of the knee. American College of Rheumatology. Arthritis Rheum. 1995;38: 1541-1546.

(9) Deyle GD, Henderson NE, Matekel RL, et al. Effectiveness of manual physical therapy and exercise in osteoarthritis of the knee: a randomized, controlled trial. Ann Intern Med. 2000;132:173-181.

(10) Beard DJ, Dodd CA, Trundle HR, Simpson AH. Proprioception enhancement for anterior cruciate ligament deficiency: a prospective randomised trial of two physiotherapy regimes. J Bone Joint Surg Br. 1994;76:654- 659.

(11) Fitzgerald GK, Axe MJ, Snyder-Mackler L. The efficacy of perturbation training in nonoperative anterior cruciate ligament rehabilitation programs for physically active individuals. Phys Ther. 2000;80:128-140.

(12) Ihara H, Nakayama A. Dynamic joint control training for knee ligament injuries. Am J Sports Med. 1986;14:309-315.

(13) Thordarson DB. Running biomechanics. Clin Sports Med. 1997;16: 239-247.

(14) Schmidt RA. Organizing and scheduling practice. In: Schmidt RA, ed. Motor Learning and Practice: From Principles to Practice. Champaign, Ill: Human Kinetics Books; 1991:199-225.

(15) Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis. 1957;16:494-502.

(16) Irrgang JJ, Snyder-Mackler L, Wainner RS, et al. Development of a patient-reported measure of function of the knee. J Bone Joint Surg Am. 1998;80:1132-1145.

(17) Irrgang JJ. Development of a Health Related Quality of Life Instrument to Assess Physical Function Related to Pathology and Impairment of the Knee [doctoral dissertation]. Pittsburgh, Pa: University of Pittsburgh, 1999.

(18) Thachuk C, Irrgang JJ, Starz TW, Levitt DA. Validity of the knee outcome survey in patients with osteoarthritis of the knee. Arthritis Care and Research. 1997;40:S174.

(19) Thachuk C, Irrgang JJ, Starz TW. Responsiveness of a specific measure of physical function of the knee as compared to a general measure of health status. Arthritis Rheum. 1998;41:S227.

(20) Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol. 1988;15:1833-1840.

(21) Bellamy N, Kean WF, Buchanan WW, et al. Double blind randomized controlled trial of sodium meclofenamate (Meclomen) and diclofenac sodium (Voltaren): post validation reapplication of the WOMAC Osteoarthritis Index. J Rheumatol. 1992;19:153-159.

(22) Hawker G, Melfi C, Paul J, et al. Comparison of a generic (SF-36) and a disease specific (WOMAC) (Western Ontario and McMaster Universities Osteoarthritis Index) instrument in the measurement of outcomes after knee replacement surgery. J Rheumatol. 1995;22: 1193-1196.

(23) Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function. 4th ed. Baltimore, Md: Williams & Wilkins; 1993.

(24) Magee D. Orthopaedic Physical Assessment. 2nd ed. Philadelphia, Pa: WB Saunders Co; 1992.

(25) McClure PW, Rothstein JM, Riddle DL. Intertester reliability of clinical judgments of medial knee ligament integrity. Phys Ther. 1989: 69;268 -275.

(26) Cooperman JM, Riddle DL, Rothstein JM. Reliability and validity of judgments of the integrity of the anterior cruciate ligament of the knee using the Lachman's test. Phys Ther. 1990:70;225-233.

(27) Rubinstein RA, Shelbourne KD, McCarroll JR, et al. The accuracy of the clinical examination in the setting of posterior cruciate ligament injuries. Am J Sports Med. 1994:22;550-557.

(28) Hurley MV, Scott DL, Rees J, Newham DJ. Sensorimotor changes and functional performance in patients with knee osteoarthritis. Ann Rheum Dis. 1997;56:641-648.

GK Fitzgerald, PT, PhD, OCS, is Assistant Professor, Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, 6035 Forbes Tower, Pittsburgh, PA 15260 (USA) ([e-mail]). Address all correspondence to Dr Fitzgerald.

JD Childs, PT, MPT, MBA, OCS, CSCS, Capt, US Air Force, is a doctoral student in the Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh.

TM Ridge, PT, MS, CSCS, is Staff Physical Therapist, Center for Sports Medicine, University of Pittsburgh Medical Center, and Adjunct Instructor, Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh.

JR Irrgang, PT, PhD, ATC, is Assistant Professor, Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh.

All authors provided concept/research design. Dr Fitzgerald, Capt Childs, and Dr Irrgang provided writing. Ms Ridge provided data collection, project management, and the patient. Capt Childs also provided project management.