PRIMARY SYNOVIAL CHONDROMATOSIS is a rare. Synovial Chondromatosis in an Elite Cyclist: A Case Report CLINICAL NOTE

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1 860 CLINICAL NOTE Synovial Chondromatosis in an Elite Cyclist: A Case Report David A. Doward, MD, Megan L. Troxell, MD, Michael Fredericson, MD ABSTRACT. Doward DA, Troxell ML, Fredericson M. Synovial chondromatosis in an elite cyclist: a case report. Arch Phys Med Rehabil 2006;87: Primary synovial chondromatosis is a rare disorder that can present as chronic hip and groin pain. It is characterized by formation of osteocartilaginous nodules arising from the synovium. We report the first case, to our knowledge, of an Olympic-caliber cyclist, in her mid thirties, with primary synovial chondromatosis of the left hip. Clinical examination showed decreased internal rotation, external rotation, forward flexion, and abduction of the left hip. A radiograph of the left hip showed slight hip-joint narrowing centrally. A magnetic resonance imaging arthrogram showed a small anterior labral tear and innumerable small intermediate-intensity filling defects situated diffusely within the joint fluid. Fluoroscopically guided injection of the left hip with local anesthetic and cortisone produced temporary pain relief. Conservative treatment was marginally helpful. Results of a rheumatology workup were unremarkable. Arthroscopic removal of loose bodies and synovectomy were performed. The diagnosis of primary synovial chondromatosis was confirmed by histologic examination. At the 17-month follow-up, our patient was essentially pain free and had returned to her previous athletic activities. Key Words: Case report; Chondromatosis, synovial; Rehabilitation by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation PRIMARY SYNOVIAL CHONDROMATOSIS is a rare condition characterized by formation of osteocartilaginous nodules originating from the synovium. 1 It is thought to be due to synovial proliferation and metaplasia, 2 which was first described by Reichel 3 in Most patients complain of a several-year history of joint pain, swelling, and loss of joint motion (signs of advanced disease) before diagnosis is made. Other monoarticular disease entities such as pigmented villonodular synovitis (PVNS) must be ruled out. Imaging studies can aid in diagnosis. Malignant transformation has been reported in cases involving repeated recurrence after treatment, but this is rare. 4,5 Without intervention, the disease can progress, the joint can deteriorate, and secondary osteoarthritis can occur. Early recognition and treatment are the keys to preventing these sequelae. From the Department of Orthopaedic Surgery, Division of Physical Medicine and Rehabilitation (Doward, Fredericson) and Department of Pathology (Troxell), Stanford University School of Medicine, Stanford, CA. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to David A. Doward, MD, 400 E 71st St, #21-I, New York, NY 10021, dadoward@yahoo.com /06/ $32.00/0 doi: /j.apmr In this clinical note, we report the first case, to our knowledge, of an elite cyclist with synovial chondromatosis of the hip joint and discuss clinical findings, diagnosis, and treatment. CASE DESCRIPTION An Olympic-caliber cyclist, in her mid thirties, presented with a 1-year history of progressive left-hip and groin pain that occasionally radiated to the anterior aspect of her thigh. She also complained of left-hip tightness. She described her pain as an intermittent, deep, dull, achy pain that averaged 2 to 4 out of 10 on a numeric pain rating scale. Her symptoms initially began with running but progressed to occur with walking, cycling, and lying on the hip. She noted a feeling of left-hip weakness or of giving out with prolonged walking. Clinical examination showed decreased internal rotation, external rotation, forward flexion, and abduction of the left hip compared with the right; there were subjective complaints of deep hip pain with external rotation. Thomas, Ely, and Faber test results were positive on the left side. A radiograph of the left hip showed slight hip-joint narrowing centrally (fig 1). Clinical evaluation at this point suggested a labral tear versus an osteochondral defect (appendix 1). A magnetic resonance imaging (MRI) arthrogram showed a small anterior labral tear and innumerable small intermediate-intensity filling defects situated diffusely within the joint fluid thought to be consistent with extensive reactive synovitis in the left hip (fig 2); other disease entities were believed to be less likely (including synovial chondromatosis, inflammatory arthropathy, and PVNS). Fluoroscopically guided injection of the left hip with a long-acting local anesthetic and cortisone was performed diagnostically and therapeutically to target the suspected inflammatory/reactive condition; it produced marked improvement of the patient s left hip pain for approximately 1 week. Nonsteroidal anti-inflammatory medications, swimming, oral prednisone, massage, and ice were only marginally helpful; physical therapy aggravated her symptoms. Results of a rheumatology workup were as follows: an erythrocyte sedimentation rate of 7mm/h; C-reactive protein level of 0.3mg/L; rheumatoid factor level of less than 20ng/mL, negative test results for antinuclear antibody, white blood cell count of 5.7 g/ml, and positive test results for human leukocyte antigen B27 (HLA-B27). The differential diagnosis included noninflammatory etiologies for monoarticular arthritis such as PVNS and synovial chondromatosis (appendix 2). Arthroscopic removal of loose bodies was recommended and performed. Operative evaluation showed no real labral tear but damage at the labral cartilaginous junction anteriorly, some damage to the femoral head, and hundreds of cartilaginous loose bodies within the hip joint (fig 3). A large capsulectomy with ablation of the synovium in the inferior capsule, removal of all loose bodies, synovectomy, and contouring of the damaged femoral head and neck were performed. The specimen sent for pathologic study consisted of 35 fragments of nodular but smoothsurfaced cartilage fragments measuring cm in aggregate, varying in size from 0.1 to 0.8cm in the greatest dimension (fig 4). Histologically, the fragments had a nodular appearance and consisted of hyaline cartilage; they were surrounded by fibrous tissue and an overlying synovial layer (fig 5). The appearance was characteristic of synovial chondromatosis.

2 SYNOVIAL CHONDROMATOSIS IN AN ELITE CYCLIST, Doward 861 Seventeen months after surgery, our patient noted a few episodes of a deep aching pain in the left hip that has caused her to discontinue riding for short periods of time. Otherwise, she has had pain-free range of motion (ROM) of the hip (with some limited end-range external rotation) and has been able to return to her previous athletic activities. DISCUSSION Evaluating a patient with chronic hip and groin pain can present a diagnostic and treatment challenge. It is essential to localize the area of abnormality. Pain may originate from the hip joint and its surrounding structures, as is seen with a labral tear, osteochondral defect, hip-joint synovitis, stress fracture of the femoral neck, and trochanteric bursitis. 2,6 It also may arise from the adductor muscles where chronic muscle strain or tendinopathy occur. Injury to the pubic bones may result in a pubic ramus fracture or osteitis pubis and can be the cause of a patient s symptoms. Likewise, the lower abdominal muscles may be implicated in iliopsoas strain, rectus abdominis tendinopathy, or sports hernia. The lower thoracic spine, lumbar spine, and sacroiliac joint may refer pain to the groin. Clinicians also must consider less-common causes of pain in this region, such as intra-abdominal pathology, urinary tract and gynecologic abnormalities, and rheumatologic disorders. 6 These disease entities may be distinguished by a thorough history, physical examination, and appropriate imaging study. Our patient had a fairly classic presentation of synovial chondromatosis. Despite this, it was necessary to do a systematic workup considering etiologies of chronic hip and groin pain and rheumatologic factors to arrive at this diagnosis. Confounding data such as the HLA-B27 positive finding could have indicated that she had a spondyloarthropathy. Because there is no correlation between synovial chondromatosis and HLA-B27 it was determined to be an incidental finding. Definitive diagnosis was confirmed by biopsy. Synovial chondromatosis, also known as synovial osteochondromatosis, is a benign condition characterized by formation of osteocartilaginous nodules that originate from the synovium. 1 The synovial lining of a joint, bursa, or tendon sheath undergoes nodular proliferation, and fragments break off from the synovial surface into the joint; these fragments can grow, calcify, or ossify. 7 It is typically a monoarticular process affecting primarily the large joints (knee, hip, elbow, ankle, shoulder); however, it may involve any synovial surface (including the extra-articular bursa), and multijoint involvement has been reported. 8,9 There is a 2- to 4-fold greater risk of occurrence for men compared with women, 7 and most present during the third to fifth decades of life with a peak incidence in the fifth. 10 Most patients describe a several-year history of joint pain and swelling associated with loss of joint motion and/or a history of locking; however, painless cases have been reported. 11 Intermittent episodes of the joint giving way also may be present. 2 The cause of primary synovial chondromatosis is unknown. 1 There is no evidence to suggest a correlation with family history or previous trauma. The pathogenesis is theorized to be a reactive metaplastic process. However, there is recent evidence to suggest that the process may be more neoplastic in nature. 12 This is based on the reported cases of chondrosarcoma originating from synovial chondromatosis 13 and research indicating that clonal proliferation is the result of somatic mutations. Currently, the relative risk of malignant transformation is determined to be 5%. 11 Three stages of the disease pathogenesis have been described: (1) active intrasynovial disease with no free, loose bodies; (2) osteochondral nodules in the synovial membrane Fig 1. Anterior radiographic view showing mild left-hip narrowing centrally. and osteochondral bodies lying free within the joint cavity; and (3) multiple free osteochondral bodies, apparently produced by previously active but now quiescent intrasynovial disease. 14 Purists distinguish primary synovial chondromatosis from secondary synovial chondromatosis, which involves an initial predisposing, unrelated articular process (eg, osteoarthritis, rheumatoid arthritis, osteochondritis dissecans, avascular necrosis) leading to joint disintegration, intra-articular fragment production, synovitis, and eventually synovial metaplasia. 7 The course of the disease is relatively benign because the proliferative process is only disruptive to the joint and can be surgically treated. Although these osteocartilaginous nodules can recur, they do not metastasize (unless there is malignant transformation, which is rare) and place the host at increased risk of mortality. Late recognition and treatment of the disease makes the outcome of secondary arthritis more likely. Synovial chondromatosis is diagnosed by history, physical examination, and imaging studies. 2 Plain radiographs are frequently diagnostic because they show characteristic features of multiple (usually 5) calcified or osseous bodies within the joint or bursa. 1 When fragments are not calcified, intrasynovial fragments may not be seen on plain radiographs, and arthrographic studies are required to show the bodies. Pressure erosions and cyst formation can be seen in adjacent bone, although this is more typical with lax capsules, such as the hip. A similar observation may be found in patients with PVNS. Degenerative joint disease with osteophytes that have broken off into the joint also must be considered in the differential diagnosis; this can usually be distinguished from synovial chondromatosis by the number of loose bodies seen in the joint (usually 5 with synovial chondromatosis). Computed tomography imaging can be used to show noncalcified bodies and possible hip-joint erosions. Ultrasound also may be used to show typical features of the disease such as synovial membrane thickening. 15 Bone scintigraphy will show nonspecific increased uptake depending on the activity of the process. 16 T1-weighted and proton density weighted MRI often shows multiple rounded bodies that are isointense or hypointense relative to muscle. T2- weighted images may show areas of high intensity consistent with joint effusion and synovial thickening. The distinguishing characteristic of synovial chondromatosis is calcification that appears as

3 862 SYNOVIAL CHONDROMATOSIS IN AN ELITE CYCLIST, Doward Fig 2. (A) Axial T1 gadolinium hip arthrogram showing multiple filling defects in synovium. (B) Axial T2 fat-suppressed image showing intermediate filling defects in bright joint fluid lower in the hip joint. Fluid anteriorly is anesthetic related to the hip. (C) Sagittal T1 fat-suppressed gadolinium arthrogram showing normal anterior labrum. (D) Sagittal T2-weighted image showing a small anterior labral tear and intermediate low-signal filling defects in the hip fluid.

4 SYNOVIAL CHONDROMATOSIS IN AN ELITE CYCLIST, Doward 863 Fig 3. (A D) Arthroscopic view of cartilaginous loose bodies in hip joint. signal voids in the synovium. On MRI, synovial chondromatosis may appear somewhat similar to PVNS, but the 2 conditions are easily differentiated by using plain radiographs.7 PVNS is a benign proliferative disorder that can be confused with synovial osteochondromatosis.17 It also affects synoviallined joints, bursae, and tendon sheaths and must be considered in the differential diagnosis. It has a clinical presentation similar to that of synovial chondromatosis, but calcifications are not a usual feature; therefore, plain radiographs are helpful in distinguishing the 2 disorders.7 Other disease entities to exclude are rice bodies of tuberculosis, rheumatoid arthritis, gout, hemochromatosis, hemophilic arthropathy, amyloid arthropathy, synovial sarcoma, secondary osteoarthritis, and synovial hemangioma.17 Without intervention, the disease can progress, the joint can deteriorate, and secondary osteoarthritis can occur.7,11 Therefore, early recognition and treatment are critical. The treatment of synovial chondromatosis is surgical: either open or arthroscopic removal of loose bodies with or without synovectomy.2,17 Removal of loose bodies alone does not halt progression of the disease. Synovectomy is controversial and has been described as essential,18 harmful,19 or useless.14 With complete synovectomy, hip dislocation is necessary, and long-term clinical outcomes with this procedure are excellent (providing that all loose bodies are removed).20 Arthroscopic synovectomy is safe and effective and allows for faster rehabilitation.2,17 Kim et al21 have described excellent results with arthroscopic removal of loose bodies and partial synovectomy in 4 patients with synovial chondromatosis. We elected this procedure for our patient. The recurrence rate after surgery is reported to be as high as 15%, possibly because of inadequate removal of loose bodies and synovium at time of initial surgery.4,11 Fig 4. Specimen consists of hyaline cartilage and has typical nodular architecture. Nodules are surrounded by fibrous tissue and an overlying synovial layer. Fragments measure 3ⴛ2ⴛ0.8cm in aggregate and vary in size from 0.1 to 0.8cm in the greatest dimension.

5 864 SYNOVIAL CHONDROMATOSIS IN AN ELITE CYCLIST, Doward Fig 5. (A) Histology slide showing clustered chondrocytes with pyknotic dark-staining nuclei. (B) Magnified view showing some atypical features including large nuclei with dispersed chromatin and nucleoli. CONCLUSIONS To our knowledge, there are no other case reports of this condition in athletes. Although we do not know if our patient s sport involvement played a role, it is possible that the high-level hip demands of cycling contributed to this condition. Also, with the increased awareness of labral tears as a source of hip pain in athletes, it is important for physicians to keep other causes of hip synovitis in mind. Seventeen months after surgery, our patient has pain-free ROM of the left hip and has been able to return to previous athletic activities. APPENDIX 1: DIFFERENTIAL DIAGNOSIS OF CHRONIC HIP AND GROIN PAIN Adductor muscles Osteitis pubis Pubic symphysitis Trochanteric bursitis Nerve entrapment Referred back/sacroiliac pain Stress fracture Inguinal hernia Iliopsoas strain/bursitis Snapping hip Hip joint Synovitis Osteoarthritis Labral tear Osteochondral defect Infection Intra-abdominal abnormality Spondyloarthropathy Avascular necrosis Tumor APPENDIX 2: DIFFERENTIAL DIAGNOSIS FOR MONOARTICULAR ARTHRITIS Inflammatory Infectious Disseminated gonorrhea Tuberculosis (rice bodies) Fungi Lyme arthritis Endocarditis Crystals Monosodium urate Calcium pyrophosphate Hydroxyappatite Spondyloarthropathy Ankylosing spondylitis Reiter s syndrome Psoriatic arthritis Noninflammatory Trauma/fracture Osteoarthritis Osteonecrosis Neoplasm Benign PVNS Synovial chondromatosis Chondroma Synovial hemangioma Fibroma Lipoma Malignant Synovial sarcoma Chondrosarcoma Clear cell Epitheliod References 1. Mora R, Soldini F, Raschella F, Paparella F, Belluati A, Basile G. Primitive synovial chondromatosis of the hip. Ital J Orthop Traumatol 1992;18: Coles MJ, Tara HH Jr. Synovial chondromatosis: a case study and brief review. Am J Orthop 1997;26: Reichel PF. Chondromatose der Kniegelenkkapsel. Arch Klien Chir 1900;61: Davis RI, Hamilton A, Biggart JD. Primary synovial chondromatosis: a clinicopathologic review and assessment of malignant potential. Hum Pathol 1998;29:683-8.

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