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Knee extension loss secondary to a "Cyclops-Like" gouty tophus: a case report and literature review.

Abstract

While gouty arthritis of the knee is not uncommon, associated mechanical block to extension is a rarely seen complication. This report presents a unique case of extension loss due to a single, isolated intra-articular gouty tophus. Only a few similar reports have been described in the literature involving cases that are often initially suspected to be related to inherent structural knee pathology as opposed to a systemic condition or illness.

Extension loss in the knee joint is a debilitating condition. It increases contact forces between the patella and femur and can cause patients to ambulate with a flexed knee and ultimately lead to a fixed contracture. (1) Any loss greater than 5[degrees] typically results in a noticeable limp. (2) Classic causes of extension loss include post-traumatic fibrotic lesions, internal derangement of ligaments or cartilage, displaced meniscal tears, cyclops lesions following ACL reconstruction, degenerative changes, and loose bodies. While gout is not a typical cause of diminished knee range of motion (ROM), a few cases have been described in the literature in which flexion was typically impacted more significantly than extension. (3-5)

Gout is an inflammatory crystal arthropathy, resulting from abnormal purine metabolism. Symptoms of acute gouty arthritis typically include joint pain, swelling, and redness, with the knee being the third most commonly involved joint, behind the first metatarsophalangeal joint and ankle. (6) The chronic stage of gouty arthritis is characterized by the presence of tophi. The tophus is a nodule composed of a central crystalline core of monosodium urate (MSU) crystals surrounded by a fibrovascular zone made up of inflammatory cells and matrix proteins. (7) Tophi typically present within subcutaneous tissue, joints, tendons, and ligaments, and have been implicated in the development of structural joint damage. (7)

Case Report

A 41-year-old male presented for evaluation of acute, atraumatic onset of left knee pain. The patient had a long history of mild, intermittent knee pain, which he related to an old football injury. He described having knee pain that spontaneously worsened over the previous 2 weeks prior to presentation. The patient had a history of gout but reported no prior episodes of inflammatory arthritis and had not been on any medical therapy or prophylactic treatment. On physical examination, he had a small effusion with full ROM from -5[degrees] to 135[degrees] of flexion. There was no joint line tenderness, and the knee was stable to varus and valgus stress testing. Lachman and pivot shift tests were negative. Plain radiographs and MRI were unremarkable other than evidence of a chronic appearing partial tear of the ACL. The patient was treated with a course of physical therapy with gradual resolution of symptoms.

Seven months later, the patient presented again with pain and swelling of the left knee as well as a firm block to terminal extension. On exam, the patient's passive ROM was 25[degrees] to 115[degrees] of flexion. There was a small effusion and tenderness to palpation over the medial joint line. The patient reported experiencing an acute gouty attack of his left great toe 2 weeks prior, coinciding with the onset of his knee pain. Repeat MRI demonstrated a chronic partial tear of the ACL with grossly normal menisci, a popliteal cyst, and moderate-sized joint effusion with synovitis (Fig. 1).

The patient was referred to his primary care physician for medical management of his gout. Two weeks later his pain and swelling remained unchanged, and his ROM remained limited to 25[degrees] to 120[degrees] of flexion. Once again, there was felt to be a firm mechanical block to terminal extension and consequently arthroscopic surgery was recommended.

The knee was examined under anesthesia, revealing once again a firm, fixed extension block. A systematic arthroscopic evaluation was then performed. There was diffuse synovitis throughout the suprapatellar region. The patellofemoral articular cartilage appeared normal. A small crystalline deposit was noted on the articular cartilage of the anterior aspect of the medial femoral condyle (Fig. 2), and the medial meniscus was probed and found to be intact and stable. Inspection of the lateral compartment revealed a stable meniscus with normal-appearing articular cartilage.

Inspection of the intercondylar notch revealed a large, well-formed crystalline deposit, which was firmly adherent to the roof of the notch and to the ACL (Fig. 3) having the appearance of a "cyclops" lesion. The deposit was carefully excised in its entirety and sent to pathology (Fig. 4). The ACL and PCL were both intact and stable to probing. Following debridement of the notch, full, terminal extension was readily achieved without any signs of residual notch impingement. Histologic analysis confirmed the specimen to be consistent with tophaceous gout (Fig. 5).

On 4-month follow-up examination, the patient claimed to be pain free and was without complaints. On physical examination directed toward the left knee, there was no effusion with ROM of -5[degrees] to 135[degrees] of flexion, equal to the contralateral side. He had been referred to his primary care physician for medical management of his gout.

Discussion

Mechanical blockage within the knee secondary to gouty tophi has been demonstrated as a rare cause of limited ROM and locking symptoms. Internal or structural derangement of the knee is often initially suspected based on history and physical examination. Several such case reports have been described recently in the literature. (3,5,8,9)

Other unique presentations of tophaceous gout involving the knee have been described, including extensor weakness and tendonitis, (10,11) buckling of the PCL, (12) and acute rupture of the ACL. (13)

In a retrospective review of MRIs from 30 patients with tophaceous gout involving the knee, typical patterns and locations of MSU crystal deposition were characterized. (6) Of the 32 knees, 26 had multiple lesions, while only 6 had a single isolated tophus. The most common locations of deposition included the infrapatellar fat pad and anterior joint recess (87%), popliteal groove (78%), and intercondylar roof (69%). Additionally, only six patients presented with concomitant subcutaneous tophi. These investigators did not comment on the symptoms experienced by these patients.

Yu and colleagues (3) described a series of seven patients with limited knee ROM secondary to gouty tophi. Three of the patients experienced an average loss of 25[degrees] of extension. All seven patients experienced and average loss of 35[degrees] of flexion. The investigators comment that all patients' symptoms were initially thought to be due to degenerative changes or other internal derangements before MRI revealed multiple tophaceous deposits within the joints. Common sites of deposition included the infrapatellar fat pad, patellofemoral compartment, and intercondylar fossae.

Hussin and associates (8) reported on two patients with isolated extension loss; one patient presented with 10[degrees] of extension loss and the second with 30[degrees] of extension loss. Both patients were found to have multiple tophi deposits in the patellofemoral compartments and attached to the anterior horn of the medial meniscus.

Only two reports were found in the literature describing symptoms due to a single gouty tophus. Law and coworkers (5) presented a patient who complained of anterior knee pain and limited ROM from 10[degrees] to 100[degrees] of flexion, who was found to have a single tophus in the patellofemoral compartment. Espejo-Baena and colleagues (9) described a patient who presented with painful locking during extension, and was found to have a single tophus attached to the anterior horn of the lateral meniscus.

The case described in the present report is an unusual presentation of tophaceous gout with a single tophus in the intercondylar notch resulting in isolated extension loss. Based on review of the literature, the more typical presentation is diffuse tophi causing combined flexion and extension loss. Although MRI in this case failed to demonstrate or identify any deposits, no other intra-articular structural abnormalities were identified, and consequently gouty tophus should be considered as a possible cause of extension loss.

Arthroscopic treatment of the patient described in this case resulted in full restoration of ROM and function. Similar excellent outcomes have been reported by other investigators. (4,8)

Conclusions

Although rare, mechanical blockage secondary to gouty tophi should be considered as a potential etiology of knee extension loss in patients with a history of gout. While extension loss can be debilitating for patients, this condition can be treated successfully with arthroscopic debridement and excision of the deposit.

Disclosure Statement

None of the authors have a financial or proprietary interest in the subject matter or materials discussed, including, but not limited to, employment, consultancies, stock ownership, honoraria, and paid expert testimony.

References

(1.) Perry J, Antonelli D, Ford W. Analysis of knee-joint forces during flexed-knee stance. J Bone Joint Surg Am. 1975 Oct;57(7):961-7.

(2.) Laubenthal KN, Smidt GL, Kettelkamp DB. A quantitative analysis of knee motion during activities of daily living. Phys Ther. 1972 Jan;52(1):34-43.

(3.) Yu KH, Lien LC, Ho HH. Limited knee joint range of motion due to invisible gouty tophi. Rheumatology (Oxford). 2004 Feb;43(2):191-4.

(4.) Pan F, Li Q, Tang X, et al. [Method and effectiveness of arthroscopic debridement for treating gouty arthritis of the knee]. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2011 Aug;25(8):937-40.

(5.) Law YY, Lue KH, Lu KH. Gouty tophi presenting as medial patellar plica syndrome and patellofemoral disorder to limit knee range of motion. J Rheumatol. 2010 Mar;37(3):680-1.

(6.) Ko KH, Hsu YC, Lee HS, et al. Tophaceous gout of the knee: revisiting MRI patterns in 30 patients. J Clin Rheumatol. 2010 Aug;16(5):209-14.

(7.) Chhana A, Dalbeth N. The gouty tophus: a review. Curr Rheumatol Rep. 2015 Mar;17(3):19.

(8.) Hussin P, Mawardi M, Nizlan NM. The 'Chalky Culprit' of acute locked knee. G Chir. 2014 Sep-Oct;35(9-10):239-40.

(9.) Espejo-Baena A, Coretti SM, Fernandez JM, et al. Knee locking due to a single gouty tophus. J Rheumatol. 2006 Jan;33(1):193-5.

(10.) Rodas G, Pedret C, Catala J, et al. Intratendinous gouty tophus mimics patellar tendonitis in an athlete. J Clin Ultrasound. 2013 Mar-Apr;41(3):178-82.

(11.) Jabour P, Masrouha K, Gailey M, El-Khoury GY. Masses in the extensor mechanism of the knee: an unusual presentation of gout. J Med Liban. 2013 Jul-Sep;61(3):183-6.

(12.) Cetin P, Tuna B, Secil M, Akar S. Tophaceous gout causing internal derangement of knee joint. J Clin Rheumatol. 2014 Jun;20(4):235.

(13.) Hwang HJ, Lee SH, Han SB, et al. Anterior cruciate ligament rupture in gouty arthritis. Knee Surg Sports Traumatol Arthrosc. 2012 Aug;20(8):1540-2.

Caption: Figure 1 Sagittal T1 MRI of left knee.

Caption: Figure 2 Intraoperative arthroscopic image of crystalline deposit on medial femoral condyle. To view this figure in color, see www.hjdbulletin.org.

Caption: Figure 3 Intraoperative arthroscopic images of gouty tophus in the intercondylar notch. To view this figure in color, see www.hjdbulletin.org.

Caption: Figure 4 Crystalline specimen sent to pathology. To view this figure in color, see www.hjdbulletin.org.

Caption: Figure 5 Hematoxylin and eosin stained micrograph of surgical specimen evaluated at 100X magnification showing amorphous material surrounded by chronic inflammatory cells. To view this figure in color, see www.hjdbulletin.org.

Michael E. Doany, B.S., Nicole Lopez, M.D., and Andrew S. Rokito, M.D.

Michael E. Doany, B.S., New York Medical College, Valhalla, New York. Nicole Lopez, M.D., and Andrew S. Rokito, M.D., Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, New York.

Correspondence: Michael E. Doany, B.S., New York Medical College, 1003 Old Farm Road, Valhalla, New York, 10595; mdoany@gmail.com.
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Author:Doany, Michael E.; Lopez, Nicole; Rokito, Andrew S.
Publication:Bulletin of the NYU Hospital for Joint Diseases
Geographic Code:1USA
Date:Jul 1, 2017
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