Comparison of the effects of exercise in water and on land on the rehabilitation of patients with intra-articular anterior cruciate ligament reconstructions.

Rehabilitation following anterior cruciate ligament (ACL) reconstruction has evolved over the past few decades and is considered important in guaranteeing a beneficial outcome following surgery.[1] Advances in surgical approaches, such as graft placement and graft fixation, and the use of arthroscopically assisted procedures have influenced rehabilitation, as have knowledge of stress-strain patterns in the ACL during various exercises.[2] Twelve-month protocols requiring immobilization and non-weight bearing[3] have given way to accelerated protocols permitting immediate weight bearing, no immobilization, and return to activity within 6 months.[2] Primary goals continue to be the recovery of joint range of motion (ROM), quadriceps femoris muscle force-generating capability, and ambulatory skills.[2] Attaining these goals, however, may be delayed by postoperative joint effusion and the persistence of pain. Early phases of rehabilitation must minimize the deleterious effects of surgery through ROM and muscle strengthening exercises while ensuring that each activity is performed without overstressing the ACL grafts.[4,5]

Electromyographic biofeedback[5,6] and neuromuscular electrical stimulation[7,8] are two modalities used in the early phases of rehabilitation following ACL reconstruction to reduce muscle atrophy and to facilitate strengthening. The effectiveness of these modalities in improving quadriceps femoris muscle force in subjects with ACL reconstruction has been measured by isokinetic dynomometry.[6,7] These studies, however, applied feedback or neuromuscular electrical stimulation during isometric quadriceps femoris exercises, and this approach may not simulate functional activities.

We believe knee extension exercises should be designed to simulate functional activities. "Closed-chain" knee extension has been advocated as a safe exercise for patients after ACL reconstruction.[9] These exercises involve applying resistance through the terminal joint of a limb segment, which restrains the joint's free movement (eg, rising from a chair), whereas "open-chain" exercises involve applying resistance to an extremity in a way that the distal joint is free to move (eg, kicking into the air).[10] Although both of these forms of exercise can address the physical impairments of patients following ACL reconstruction, research suggests that closed-chain exercises are safer than open-chain exercises because there is less stress on the graft.[11-13] Despite this fact, some subjects experience increased pain and knee effusion following closed-chain exercises.14 Therefore, performing closed-chain exercises in an environment in which the forces around the knee joint are reduced may aid in reducing knee pain and joint effusion.

Exercises in water could expedite rehabilitation because of the decreased stress on the joints, improved circulation, and facilitated movement that occur in water.[15,16] Researchers have analyzed limb movement in water[17-19] and have compared different aquatic exercise devices,[20-22] but few studies have quantified gains in muscular force that occur following an aquatic exercise program. Bartow and Diamond[23] have concluded that exercises performed using water as resistance can increase the torque-generating capabilities of the thigh musculature in healthy subjects. Gehlsen et al[24] have made similar conclusions in patients with multiple sclerosis, but no control group was used for comparison.

Napoletan[25] found that in subjects with ACL reconstructions, underwater treadmill ambulation in conjunction with traditional rehabilitation was more effective in retarding thigh atrophy than traditional rehabilitation alone. Thigh atrophy, however, is only one measure of recovery. Whether rehabilitation in water will be different from traditional rehabilitation in reducing knee joint laxity, enhancing muscle force, and improving functional outcomes in subjects with intra-articular ACL reconstructions is uncertain.

The purpose of this study was to determine whether exercises in a pool will lead to less joint effusion, less thigh atrophy, increased ROM and thigh musculature strength, and less difficulty with activities of daily living in patients after intra-articular ACL reconstruction compared with exercises on land. An effort was made to match specific exercises in both groups so that each program was identical and only the rehabilitation environment was manipulated.

Method

Subjets

Twenty subjects (14 male, 6 female) ranging in age from 16 to 44 years (X=29.0, SD=7.8) participated in this study. All subjects had undergone arthroscopically assisted intra-articular ACL reconstruction using a bonepatellar tendon-bone autograft, performed by the same orthopedic surgeon. Subjects who had prior ACL surgery to either knee or who had a meniscus repair at the time of surgery were excluded from the study.

Procedure

During the preoperative visit, subjects were familiarized with the study and postoperative rehabilitation protocols were explained. Each subject signed an informed consent statement, written to conform with the guidelines of Emory University and Piedmont Hospital (Atlanta, Ga), and a questionnaire was administered. Subjects were assigned to either a traditional rehabilitation (TR) group or a pool rehabilitation (PR) group using the following method of group assignment. The first 2 subjects were randomly assigned to one of the two groups using a coin toss. The next 2 subjects recruited were placed in opposite groups of the first 2 subjects. This procedure was continued for every 4 subjects until 20 subjects were recruited. As a result, 6 men and 4 women were placed in the PR group and 8 men and 2 women were placed in the TR group. This method of group assignment was used to evenly distribute subjects between the two groups over time, while also incorporating random assignment to groups.

Week 1 Exercises for Both

Groups

During the first postoperative session, patients in both groups were instructed in an identical program (Tab. 1), which they performed at home twice per day. The first week of postoperative rehabilitation consisted of three or four treatment sessions in which one of the authors reviewed the home program to ensure that the exercises were done safely and independently. To facilitate passive knee extension, each subject was positioned prone and the involved leg (from the superior third of the tibia to the foot) was placed off the side of a treatment table or bed, letting gravity pull the knee into extension. Resistance for the straight leg raises and leg curls was added using variable-resistance cuff weights. Subjects initiated each exercise, performing three sets of 10 repetitions without weight and progressing until they could perform three sets of 15 repetitions without difficulty. Subjects then added 0.9 kg (2 lb) to the cuff weight and repeated the progression starting with three sets of 10 repetitions. This procedure was continued, and resistance was added in 0.9-kg increments (most patients progressed their weight every 2-3 days). Subjects were instructed how to keep a log of their home exercise program, which was checked by one of the authors to help assess compliance.

Weight Bearing

Gait training was also initiated on the first postoperative session with axillary crutches and a hinged knee brace. The braces were locked in fun extension for the first 4 to 7 days, and subjects were instructed to bear as much weight as they could tolerate. Subjects were progressed from two crutches to one crutch between the 4th and 7th postoperative days and were usually off the crutch by the 10th postoperative day. The hinged knee brace was unlocked at the beginning of the 2nd week, permitting 90 degrees of knee flexion. The ROM of the braces were increased to 120 degrees by the beginning of the 3rd postoperative week, and subjects were out of the brace by the 6th postoperative week.

Rehabilitation Programs

During the second through the eighth postoperative weeks, the TR group performed a land rehabilitation program and the PR group performed a similar program in the water (Tab. 1). Both programs were performed three times per week in the same sequence.

Table 1. Rehabilitation Programs
Week 1 and Home Program Exercises (Both Groups)

1. Wall slides: 25 repetitions
2. Active-assistive range of motion: 25 repetitions
3. Passive knee extension: 10 minutes
4. Hamstring muscle and calf stretching: 10 minutes each
5. Quadriceps femoris muscle sets
6. Straight leg raises(a): 3 sets x 10 repetitions for hip
   flexion, adduction, adduction, and extension
7. Active knee flexion(a): 3 sets x 10 repetitions
8. Toe raises: 3 sets x 10 repetitions
9. Partial wall squats (usually added to the home program after
first week): 3 sets x 10 repetitions

Week 2-8 Exercise Programs
Traditional Rehabilitation Group

1. Stationary cycling: 10 minutes
2. Gait training without brace, alternating forward and
   backward
   ambulation: 10 min
3. Side step-ups, front step-ups, step-downs: beginning with 3
   sets
   of 10 repetitions, progressing to 3 sets of 15 repetitions
4. Hip flexion, extension, abduction, adduction in standing
   using a
   wall pulley with 4.54-kg (10-1b) plates: beginning with 3
   sets of 10
   repetitions, progressing to 3 sets of 15 repetitions
5. Knee flexion in sitting: 3 sets of 10 repetitions; boot:
   beginning
   with 3 sets of 10 repetitions, progressing to 3 sets of 15
   repetitions

Pool Rehabilitation Group

1. Stationary cycling: 10 minutes(b)
2. Gait training without brace, alternating forward and backward
   ambulation: 10 min
3. Side step-ups, front step-ups, step-downs: beginning with 3
   sets of
   10 repetitions, progressing to 3 sets of 15 repetitions(c)
4. Hip flexion, extension, abduction, adduction in standing
   using the
   Hydrotone resistance boot: beginning with 3 sets of 10
   repetitions
   and progressing to 3 sets of 15 repetitions
5. Knee flexion in standing using the Hydrotone resistance boot:
   beginning with 3 sets of 10 repetitions and progressing to 3
   sets of
   15 repetitions

(a) Cuff weights were added to straight leg raises and knee flexion
in increments of 0.91 kg (2 lb).

(b) Stationary cycling in the pool rehabilitation group used a
peddling device (see Fig. 1) rather than a stationary bicycle.

(c) Step-ups in the water were done with 20.32-cm (8-in) and
40.64-cm (16-in) steps.

Subjects in the TR group warmed up with 10 minutes of stationary cycling, followed by 10 minutes of gait training (alternating forward and backward walking) and 5 minutes of passive stretching. The PR group warmed up with the same exercises, but used a pedalling device underwater (Fig. 1) instead of a stationary bicycle.

Subjects in the TR group initiated closed-chain exercises on a 5.08-cm (2-in) step. Three sets of 10 repetitions were performed, progressing to three sets of 15 repetitions. When subjects could perform three sets of 15 repetitions comfortably at a given height, the height was increased by 5.08 cm and they started with three sets of 10 repetitions again. Subjects usually advanced every two or three sessions and continued the same exercise progression while the height of the step was increased in increments of 5.08 cm. Subjects usually achieved a maximum height of 30.48 cm (12 in).

Subjects in the PR group initiated closed-chain exercises on a 20.32-cm (8-in) step. Subjects began with three sets of 10 repetitions and progressed until they could do three sets of 15 repetitions without difficulty. This progression usually occurred within 1 week of rehabilitation in the water. Between the second and third weeks, subjects were advanced to a 40.64-cm (16-in) step in chest-deep water and the progression format was repeated. Between the fourth and eighth weeks, subjects used the 40.64-cm step in waist-deep water to reduce the force of buoyancy on body weight, thereby increasing resistance. Exercises in waist-deep water progressed in the same manner. If subjects were able to perform three sets of 15 repetitions on the 40.64-cm step in waist-deep water without difficulty, they were positioned on a 40.64-cm step in thigh-deep water for maximal resistance and the sequencing format was repeated.

The next group of exercises consisted of standing hip flexion, extension, abduction, adduction, and knee flexion strengthening. The TR group performed these exercises using pulleys that contained a stack of 4.5-kg (10-1b) plates. Subjects initiated each exercise with a weight they could lift comfortably for three sets of 10 repetitions and progressed until they could perform three sets of 15 repetitions without difficulty. Another 4.5-kg plate was then added, and the exercise was repeated with three sets of 10 repetitions.

Hip strengthening and knee flexion exercises were done using a Hydrotone exercise boot(*) (Fig. 2). Exercises consisted of three sets of 10 repetitions for hip flexion-extension, abduction-adduction, and knee flexion. Because this study did not intend to quantify the amount of resistance in the water or to increase the surface area of the Hydrotone boot, subjects were instructed to move their involved legs through the water as fast as they could. As symptoms decreased and muscle performance improved, subjects increased the speed and created more resistance.

Data Collection

Arthrometric measurements. Joint laxity was measured preoperatively and at 8 weeks following surgery. Measurements were made by one of two physical therapists (BJT and JC) using a KT-1000 knee arthrometer.([dagger]) This device has the highest diagnostic accuracy of five different arthrometric devices.[26] Anterior drawer testing was performed with the knee flexed 30 degrees. Anterior displacement of the tibia on the femur was measured (in millimeters) during 6.8-kg (15-1b) and 9.1-kg (20-1b) Lachman tests. Greater forces were not used in fear of over-stressing the graft during this critical period of graft healing. The testers maintained 100% agreement, within 0.5 mm, both with a prior reliability study and throughout this study.

Muscle performance measurements. Isometric and isokinetic peak knee torques were measured at the end of the eighth week of rehabilitation and compared between groups. An electromechanical dynamometer([double dagger]) and LIDO[R] AC+ software (version 5.1)([double dagger]) were used to calculate and record peak torque (in foot-pounds), and gravity-corrected measurements were obtained. According to the manufacturer, the dynamometer's accuracy is self-calibrated through the computer software package. One tester, who was blind to group assignment, performed all the testing.

During the testing session, subjects were positioned with their hips in 80 to 90 degrees of flexion. The hips and tested limb were stabilized with Velcro[R]([sections]) straps across the pelvis and over the thigh. Subjects were instructed to grasp the handrails during the test. The axis of rotation of the dynamometer was aligned with that of the knee, and the lever arm pad was placed 7.62 cm (3 in) below the tibial tubercle. Subjects were allowed a short period of familiarization at each speed.

Isometric testing consisted of three maximal 5-second repetitions with the knee flexed 85 degrees to measure knee extension torque and three maximal 5-second repetitions with the knee flexed 60 degrees to measure knee flexion torque. Subjects were given a 30-second rest period between repetitions. The highest torque value was recorded.

Isokinetic testing consisted of three separate contractions at 90[degrees]/s with a 30-second rest period between repetitions. Isokinetic extension was tested from 80 to 40 degrees of knee flexion, and isokinetic flexion was tested from 0 to 70 degrees of knee flexion. Isokinetic extension was done separately from isokinetic flexion to prevent possible shearing during changes in direction. The maximum peak torque for the three repetitions was recorded for each of the four tests. All subjects were tested in the same order.

Passive range of motion measurements. Passive range of motion (PROM) measurements for knee flexion and extension were taken by one of the two physical therapists using a standard plastic goniometer (17.78 cm [7 in] long with a 360[degrees] scale and 1[degree] increments). The testers maintained 100% agreement, within 5 degrees, both with a prior reliability study and throughout this study.

Passive range of motion was measured at the beginning of each treatment session at 2, 4, 6, and 8 weeks postoperatively. Subjects were allowed a 3-minute warm-up, which consisted of self-stretching within their available ROM. Both measurements were taken with subjects positioned supine. Knee extension measurements were taken with a towel roll under the heel of the involved extremity. Knee flexion measurements were taken with the hip maintained at 90 degrees of flexion, while the heel was moved toward the buttocks. End-range was determined by applying overpressure until firm resistance was met. The maximum value of three measurements was recorded.

Girth measurements. Girth measurements were taken by one of the two physical therapists during the preoperative visit and at 2, 4, 6, and 8 weeks following surgery. Measurements were taken at the mid-patella level and 15.24 cm (6 in) above the mid-patella using a standard tape measure (increments of 0.3175 cm [1/8 in]) with subjects positioned supine with their thigh musculature relaxed. These measurement locations were used to document changes in knee joint effusion and thigh muscular atrophy. The testers maintained 100% agreement, within 0.636 cm (1/4 in), both with a prior reliability study and throughout this study.

Functional questionnaire. A functional questionnaire was administered at the end of the eighth postoperative week. The questionnaire consisted of a Lysholm scale,[27] Which quantifies the functional use of the knee joint using a scale of 0 to 100. This rating system is a self-report of the subject's perceived ability of activities such as walking, stair climbing, and squatting and is an accepted method of evaluating functional impairment.[27,28] Higher scores indicated better functional use with fewer symptoms.

Data Management and Analysis

Side-to-side differences in joint laxity measurements were calculated and used to compare the values between groups prior to surgery and 8 weeks following surgery. Mean differences were compared using an analysis of variance (ANOVA). A Tukey's pair-wise comparison was used for within-group comparisons, and a Bonferroni pair-wise comparison was used for between-group comparisons.

Measurements of isometric and isokinetic peak torque for the quadriceps femoris and hamstring muscles were normalized to the values of the uninvolved contralateral musculature and expressed as a percentage. The mean peak torque percentage and the mean Lysholm score were compared between groups using a Student's t test. The ROM measurements for weeks 2, 4, 6, and 8 were analyzed using a two-way ANOVA (groups x weeks) for repeated measures. A Tukey's pairwise comparison post hoc test for significance was used for within-group comparisons, and a Bonferroni pair-wise comparison was used for between-group comparisons.

Girth measurements were calculated from measurements of girth at mid-patella and 15.24 cm above mid-patella. Mean differences were compared at 2, 4, 6, and 8 weeks using tests identical to those undertaken for ROM. The alpha level of significance was set at .05.

Results

Results of the ANOVAs for joint laxity measurements, presented in Tables 2 and 3, showed no significant difference between groups (F=3.43, 4,04; df=1,1; P=.08, .06), indicating that neither program induced more laxity than the other. A significant effect for time did exist at both the 6.8-kg (F=8.39, df=1, P=.01) and 9.1-kg forces (F=24.0, df=1, P=.0001), indicating that both groups had significantly less joint laxity at 8 weeks after surgery compared with before surgery.

Table 2. Results of Analysis of Variance of Differences in Joint
Laxity Measurements
During a 6.8-kg (15-1b) Lachman Test

Source               df        SS           ms         F         p

Between subjects
  Groups (A)          1        21.00        21.00      3.43     .082
  Error              17        104.08        6.12
Within subjects
  Weeks (B)           1         50.84       50.84      8.39       01
  A x B               1         0.003        0.003     0.00     .984
  Error              17        103.05        6.06

Table 3. Results of Analysis of Variance of Differences in Joint
Laxity Measurements
During a 9.1-kg (20-lb) Lachman Test

Source              df       SS          ms          F       p

Between subjects
  Groups (A)         1       37.16       37.16       4.04    .06
  Error             17      156.20        9.19
Within subjects
  Weeks (B)          1      123.73      123.73      24.00    .0001
  A x B              1        0.25        0.25       0.05    .827
  Error             17       87.64        5.16

Comparison of quadriceps femoris and hamstring muscle isometric and isokinetic peak torque percentages (Tab. 4) between groups revealed no significant differences for isometric knee flexion, isometric knee extension, and isokinetic knee extension peak torque percentages. The isokinetic knee flexion peak torque percentage, however, was significantly higher for the TR group (X=96.4, SD=13.5) than for the PR group (X=81.7, SD=11.1) P=.01).

[TABULAR DATA OMITTED]

Passive range of motion measurements were recorded at weeks 2, 4, 6, and 8. Table 5 shows that there were no significant differences between groups at each measurement period (F=0.38, df=1, P=.546). As expected, there was a significant effect for time (F=116.49, df=3, P=.0001), implying that knee joint PROM for both groups improved over the 8 weeks. At 2 weeks following surgery, the first PROM measurement showed that both groups had an average of 117 degrees of knee PROM. Both groups showed progressive increments over time, averaging 20 degrees between weeks 2 and 4, 8 degrees between weeks 4 and 6, and 4 more degrees between weeks 6 and 8. Mean knee PROM for both groups at the end of the 8-week program was 150 degrees. Post hoc analysis revealed that gains in PROM were significant for both groups only during the first 6 weeks. No significant differences were noted between groups. There was no significant group x time interaction, indicating that change in PROM over time was not dependent on assignment.

Table 5. Results of Analysis of Variance of Differences Between
Groups in Recovery
of Range of Motion

Source              df      SS         ms         F       p

Between subjects
  Groups (A)         1      132.61     132.61     0.38    .546
  Error             18     6287.63     349.31
Within subjects
   Weeks (B)         3    13277.84    4425.95   116.49     .0001
   A x B             3       48.24      16.08     0.42     .737
   Error            54     2051.66      37.99

Girth measurements taken at mid-patella and 15.24 cm above mid-patella were compared between knees to determine mean differences (Tab. 6). Between-group analysis showed that the PR group had less girth than the TR group for each mid-patella measurement, but the difference was significant only at 8 weeks. No significant difference between groups was noted (F=2.09, df=1, P=.166). A time effect was shown (F=23.45, df=4, P=.0001), as both groups had a significant increase in girth at mid-patella between the baseline measurement and the second postoperative week. Additionally, both groups showed a significant decrease in girth at mid-patella after the second week, but only until week 4. At 15.54 cm above mid-patella, both groups had significant decreases in girth between the baseline measurement and the second postoperative week, but no difference existed between groups. Mean Lysholm scores were significantly higher in the PR group (X=92.2, SD=4.31) than in the TR group (X=82.4, SD=12.36) (P=.03).

Table 6. Results of Analysis of variance of Differences Between
Groups for Girth
Measurements at Mid-patella and 40 64 cm (6 in) Above Mid-patella

Source                       df     SS      ms       F         p

Mid-patella
  Between subjects
    Groups (A)                1     0.42     0.42     2.09     .166
    Error                    17     3.44     0.20
  Within subjects
    Weeks (B)                4      2.93     0.73    23.45     .0001
    A x B                    4      0.06     0.02     0.51     .730
40.64 cm above mid-patella
  Between subjects
    Groups (A)               1      0.006    0.006    0.01     .933
    Error                   17     15.53     0.80
  Within subjects
    Weeks (B)                4      5.24     1.31    22.97     .0001
    A x B                    4      0.39     0.098    1.71     .157
    Error                   68      3.88     0.06

Discussion

Lysholm scale measurements showed that the PR group scored significantly higher than the TR group at 8 weeks, indicating that this group had fewer problems with activities of daily living. Increased pain, based on the subjects' self-report, and knee swelling during activities of daily living were primarily responsible for lower scores in the TR group. The results of the laxity and girth measurements may offer possible reasons why the PR group had higher Lysholm scores.

At 8 weeks following surgery, both groups had less than 3 mm of difference in joint laxity between the involved and uninvolved knees for both the 6.8- and 9.1-kg Lachman tests. Neither program induced knee joint laxity, as a laxity difference of [less than or equal to] 3 mm is considered normal.[29] Although between-group comparisons revealed no significant difference, the within-group means at the end of 8 weeks indicated that the TR group had greater than 1.5 mm more laxity for both tests than the PR group. The inability to detect a significant difference between groups may have been due to insufficient sample size. This result may be due to the increased stresses on the knee joint during rehabilitation on land compared with in water.[15] Increased knee joint laxity in the surgical knee at 8 weeks could have resulted in increased knee joint effusion, which may have led to the lower Lysholm scores.

Girth measurements taken at 15.24 kg above mid-patella showed no significant difference between groups for atrophy of the thigh musculature. Within-group comparison, however, revealed that both groups followed the same significant changes from the presurgical measurement until the eighth postoperative week. Both groups experienced the greatest change between the presurgical measurement and the second postoperative week, with the greatest decrease in girth occurring at the fourth postoperative week. Thigh musculature atrophy is commonly observed during the acute postsurgical period due to muscle inhibition that takes place from the increased joint effusion and increased pain. DeAndrade et al[30] have shown that with increased knee joint effusion, there is less muscle output as measured by electromyographic activity.

Thigh girth began to increase after the fourth postoperative week, and the involved extremity was within 1.90 cm (0.75 in) of the contralateral extremity by the eighth postoperative week for both groups. Increases in thigh girth at this time may be attributed to several factors. As postoperative joint effusion and pain decrease while ROM increases, the thigh musculature can be exercised through a greater ROM. As exercises are performed more vigorously, muscle tissue begins to hypertrophy, resulting in greater circumferential measurements.

Girth measurements taken at mid-patella showed that the girth for the PR group was consistently less at each time period, but these differences were significant only at 8 weeks. As discussed earlier, the increased girth in the TR group may have been caused by the joint effusion resulting from greater stress on the joint during land exercises compared with water exercises. This increased joint effusion may have led to lower Lysholm scores.

Within-group comparison reveals that mid-patella girth measurements changed similarly for both groups; that is, measurements at this location were inversely related to the measurements taken at 15.24 kg above mid-patella. The greatest increase in girth was noted between the presurgical measurement and the second postoperative week, suggesting the increased joint effusion that typically occurs following surgery. These results indicate that as joint effusion decreases, muscle girth increases, with the transition occurring around 4 to 6 weeks following surgery.

Between-group comparison for peak torque percentages (PTPs) showed that the TR group had a significantly higher PTP for the hamstring muscles at 90[degrees]/s, indicating that the traditional rehabilitation approach was more effective than the pool rehabilitation approach for strengthening the hamstring muscles. This result may have occurred for two reasons. First, resistance in the water was partially determined by the speed of limb movement, which was controlled by each subject.[16] Subject effort can be affected by pain and motivation. Therefore, subjects may not have generated enough resistance to facilitate maximal strengthening. Hamstring muscle exercises in the TR group were done using weights, so resistance was not self-paced. Second, there is a difference in the type of muscle contraction that occurs on land. Empirical evidence suggests that an eccentric muscle contraction is important for restoring muscle performance.[31] This type of contraction is more likely to occur on land than in water due to increased gravitational forces.

In both groups, there was equal effectiveness in restoring quadriceps femoris muscle strength. These results also showed that greater joint effusion in the TR group did not significantly affect peak torque muscle performance. A possible reason for this finding is that all subjects were tested in the range of 85 to 40 degrees of knee flexion, rather than at the end-range where joint effusion has been shown to affect muscle performance.[30]

The mean PTPs for both groups are similar to those reported for other subjects with ACL reconstructions.[5] Other studies,[7,8] however, have demonstrated higher peak torque values. Two possible explanations for lower PTPs in this study are the type of quadriceps femoris muscle strengthening and methodological factors.

Type of Quadriceps Femoris

Muscle Strengthening

The method of quadriceps femoris muscle strengthening in both groups focused on closed-chain exercises, which may not have provided enough isolated stimulus to the quadriceps femoris muscle to facilitate maximum strength gains. Previous studies,[7,8] which demonstrated higher strength gains, applied neuromuscular electrical stimulation during open-chain knee extension exercises. Both groups in this study may have benefited from isolated knee extension exercises through a limited ROM (90[degrees] to 40[degrees] of knee flexion to ensure graft protection), as recent research findings indicate that closed-chain exercises alone may not be enough to facilitate maximum muscle performance as measured by isokinetic dynamometry.[32]

Methodological Factors

Changing the methodology may have resulted in higher mean PTPs. Performing three 5-second isometric quadriceps femoris muscle contractions resulted in donor site pain (the anatomical site at which the central third of the patellar tendon was surgically removed for use as an autograft) in some subjects in both groups, which may have altered the remaining tests. Anterior knee pain is common in the early phases of ACL rehabilitation if a patellar tendon autograft is used. Testing isometrically and at slow speeds increases the joint reaction forces around the patella, but usually is a better indicator of strength. Although strength testing in this study provided adequate graft protection, testing at faster speeds first and slower speeds at the end of the testing session might have resulted in better PTP scores. The testing procedure in this study did not take these factors into account because at the time the study was proposed, no published research had incorporated isokinetic testing at 8 weeks, using only subjects with patellar tendon autografts.

Clinical Implications

Although a primary goal in the rehabilitation of patients with ACL reconstructions is the restoration of quadriceps femoris muscle performance, the means of achieving this goal must avoid overstressing the graft and increasing joint effusion. Additionally, to expedite recovery, patients must tolerate the rehabilitation program. Some patients find postoperative exercises too uncomfortable because of age, low presurgical activity level, or low pain tolerance, and progression during the early phases of rehabilitation is limited.

Exercises in water may make the total rehabilitation program more tolerable. Although a complete aquatic exercise program may be unnecessary, augmenting a land program with pool exercises may permit loading the joint to a greater degree. For patients who are unable to tolerate traditional exercises on land, water can be used to facilitate progression to more aggressive exercises. In this study, a water environment was most beneficial for facilitating closed-chain exercises, such as gait training and step-ups, and the land pulleys appeared to be most beneficial for hamstring muscle and hip strengthening. Isolated quadriceps femoris muscle contractions in a safe range using open-chain exercises may have benefited both groups.

Patients using a pool for rehabilitation are likely to tolerate an even more aggressive rehabilitation program than that presented in this study. In this study, however, exercises in both groups had to be carefully matched to ensure that the main effect between rehabilitation programs was due to the environment. The PR group could have performed more advanced exercises, but varying the exercises would have made interpretation of results unclear because differences between groups could have then been attributed to the environment, exercises, or interaction between the two.

Conclusion

Although traditional exercises have been the treatment choice of most clinicians, the results of this study suggest that a rehabilitation program for patients with intra-articular ACL reconstructions performed in a pool is more effective in reducing joint effusion and facilitating recovery of lower-extremity function as indicated by Lysholm scores. The results also suggest that rehabilitation in water is equally effective as on land for restoring knee ROM and quadriceps femoris muscle strength, but not as effective in restoring hamstring muscle strength. Clinicians who wish to allow maximal weight bearing may find the adjunct of aquatic exercises useful. Future studies should analyze the effectiveness of a program that combines traditional and water exercises, using larger sample sizes and a longer follow-up period.

Acknowledgments

We thank Lynn Snyder-Mackler, ScD, PT, for assisting with preparation of this manuscript; Roberto Infante, PT, and the staff at Resurgeons Orthopaedics for their assistance with data collection; and Piedmont Hospital for use of their facilities.

(*) Hydrotone International Inc, 3535 NW 58th St, Ste 1000, Oklahoma City, OK 73112.

([dagger]) Medmetric, San Diego, CA.

([double dagger]) Loredan Biomedical Inc, 2121-B 2nd St, Ste 107, Davis, CA 95616.

([sections]) Velcro USA Inc, 406 Brown Ave, Manchester, NH 03108.

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BJ Tovin, PT, ATC, is Staff Physical Therapist, Physiotherapy Associates, 2770 Lenox Rd NE, Ste 102, Atlanta, GA 30324 (USA), and Director of Rehabilitation Georgia Tech Athletic Association, Atlanta, GA 30332. Mr Tovin was a student at Emory University, Atlanta, GA, at the time this study was completed in partial fulfillment of the requirements for his Master of Medical Science degree. Address all correspondence to Mr Tovin.

SL Wolf, PhD, PT, FAPTA, is Professor and Director of Research, Department of Rehabilitation Medicine, Professor, Division of Geriatrics, Department of Internal Medicine, and Associate Professor, Department of Anatomy and Cell Biology, Emory University School of Medicine, 1441 Clifton Rd NE, Atlanta, GA 30322.

BH Greenfield, PT, OCS, is Clinical Coordinator of Education and Clinic Director, Physiotherapy Associates, Jonesboro, GA 30236, and Clinical Instructor, Division of Physical Therapy, Emory University.

J Crouse, PT, is Clinical Coordinator of Physical Therapy, HealthSouth, Atlanta, GA 30342.

BA Woodfin, MD, is Orthopaedic Surgeon, Resurgeons Orthopaedics, and Team Physician, Georgia Tech Athletic Association.