Arthroscopic Management of Primary Synovial Chondromatosis of the Ankle: A Case Report and Review of the Literature

Introduction

Synovial chondromatosis (SC) is a slowly progressing, self-limited disorder of unknown etiology, characterized by synovial metaplasia within an otherwise healthy joint, resulting in the formation of loose cartilaginous bodies.¹ If left untreated, SC may lead to debilitating degenerative changes and, in rare instances, malignant transformation into chondrosarcoma.²

The estimated prevalence of SC is approximately 1 in 100,000 individuals.² It is defined by metaplastic transformation of the synovial membrane, tendon sheath, or bursae into intra-articular or juxta-articular cartilaginous or osteocartilaginous nodules.³ The disease progresses through three stages as first described by Milgram: (1) early disease without loose bodies; (2) transitional disease with active proliferation and loose bodies; and (3) late-stage disease with multiple loose bodies but no active synovitis.⁴

SC typically affects individuals between 30 and 50 years of age, with a male-to-female ratio of approximately 2:1.¹ The most commonly involved joints are the knee (65%), hip (20%), shoulder (10%), and elbow (5%).⁵ Ankle involvement is exceedingly rare, with only around 50 cases reported in the literature.

In this paper, we present a case of ankle SC in a 49-year-old female, managed arthroscopically. We also conduct a review of the literature since 2010 with the purpose of providing an updated, clinically relevant, critical synthesis comparing outcomes between open and arthroscopic approaches for surgical treatment. Relevant studies including both intra-articular and extra-articular SC of the ankle were identified through a non-systematic search of the PubMed, Embase, and Scopus databases from 2010–2024.

Case Presentation

A 49-year-old female with a medical history of palmoplantar psoriasis presented to our clinic following referral from her rheumatologist. She initially presented to her rheumatologist complaining of a 12-month history of progressively worsening right ankle pain and described a sensation of “walking on pebbles”. She also noted reduced ankle range of motion, particularly in dorsiflexion, and anterior ankle pain after prolonged standing. There was no history of trauma or previous foot or ankle injuries. Her rheumatologist then placed her on a course of nonsteroidal anti-inflammatory medications and referred her to physical therapy for conservative treatment. Plain x-ray radiographs followed by MRI were also ordered. She presented to our clinic after 14 months of her initial onset of symptoms.

Institutional approval was not required as written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Physical Exam

Physical examination revealed an antalgic gait with tenderness and mild edema over the anterior tibiotalar joint. The patient had approximately 8° of active and 10° of passive dorsiflexion, and 28° of active and 40° of passive plantarflexion. The dorsalis pedis pulse and light touch sensation were intact. There were no abnormalities in the distal interphalangeal joints, and the contralateral ankle examination was unremarkable.

Imaging

Initial radiographs showed anterior calcified loose bodies (Figure 1). Given these findings, her rheumatologist ordered an MRI, which revealed multiple intrasynovial loose bodies (1–2 cm) and synovial thickening (Figures 2–4). When the patient presented to our clinic 14 months following initial symptoms, repeat imaging confirmed persistent loose bodies, synovial hypertrophy, and moderate joint effusion prompting surgical management.

Figure 1 AP (a), lateral (b), and oblique (c) radiographs of the right ankle showing anterior calcified bodies specified by the yellow arrows. (R) refers to right. (KH) refers to radiology technician initials.

Figure 2 Axial MRI T2 of the right ankle showing anterior calcified loose bodies specified by the yellow arrows.

Figure 3 Coronal MRI T2 of the right ankle showing anterior calcified loose bodies.

Figure 4 Sagittal MRI of the right ankle with anterior calcified loose bodies specified by the yellow arrows.

Surgical Technique

Under general anesthesia, the patient was positioned supine with the right lower limb supported on a well-padded bolster. The limb was scrubbed and draped in a standard sterile fashion. Standard anteromedial and anterolateral portals were established for ankle arthroscopy.

Arthroscopic inspection revealed extensive calcified synovial loose bodies in the anterior ankle compartment along with severely inflamed synovium. Complete debridement of inflamed synovial tissue was performed, with care to avoid injury to adjacent neurovascular and tendinous structures. All accessible loose bodies were excised and sent for pathological evaluation (Figure 5). The joint was thoroughly irrigated and inspected to confirm removal of all visible loose bodies. Upon completion, passive dorsiflexion showed marked improvement. The portals were closed and a sterile dressing applied. The patient was transferred to recovery in stable condition and was allowed immediate full weight-bearing as tolerated postoperatively.

Figure 5 Arthroscopic views of the loose bodies found in the ankle specified by the yellow arrows.

Histopathological Result

Osteochondroid nodules consistent with loose bodies measuring 0.6–1cm (Figure 6) showing lobules of hyaline cartilage. Graded as Milgram stage 3 with no atypia.

Figure 6 A total of 15 loose bodies extracted from the ankle joint.

Follow Up

At one-year follow-up, the patient reported significant symptomatic improvement, including enhanced ankle stability, increased range of motion, and reduced pain. Physical examination revealed improved ankle motion with 15° of active and 20° of passive dorsiflexion, and 40° of active and 50° of passive plantarflexion. She had completed multiple sessions of physical therapy with satisfactory outcomes.

Discussion

Synovial chondromatosis (SC), also known as Reichel’s syndrome, is a rare, predominantly benign arthropathy affecting bursae, tendon sheaths, and joints. It is a metaplastic disorder in which synovial tissue transforms into cartilaginous or osteocartilaginous nodules.³

SC can be classified as either primary or secondary. Primary SC results from direct synovial metaplasia into chondrocytes, whereas secondary SC occurs secondary to chronic joint diseases such as osteoarthritis, osteochondritis dissecans, rheumatoid arthritis, or tuberculosis.⁶ Our case represents primary SC, as there was no history of trauma or preexisting joint disease.

Milgram’s pathological classification, introduced in 1977, describes SC in three stages: (1) active intrasynovial disease without loose bodies, (2) transitional disease with synovial proliferation and free bodies, and (3) multiple osteochondral bodies without active synovial disease.⁷ This staging guides management. Surgical excision is recommended for stages 2 and 3, with or without synovectomy.⁸ Conservative management may be considered in stage 1, but no cases in the literature report complete resolution without surgery.⁹

The exact pathophysiological and genetic factors contributing to the development of synovial chondromatosis are not entirely understood. However, several papers have attempted to explain certain aspects related to the genetic and molecular basis of this disease. While being traditionally considered a benign process, some of these studies suggest that SC may in fact be a neoplastic condition driven by specific genetic alteration and molecular pathways. One of the key pathological events reported by Agaram et al is the recurrent fibronectin 1 (FN1) and activin receptor 2A (ACVR2A) gene fusion, identified in a significant number of cases, which serves as a leading molecular driver of the disease.¹⁰ Additionally, a study by Buddingh et al has reported recurrent karyotypic abnormalities on chromosome 6 in 3 cases of SC.¹¹ Both of these aforementioned studies may indicate a neoplastic origin of SC rather than metaplastic. At a cellular level, there is abnormal proliferation and differentiation of specific progenitor cells. A paper by Li et al identified an increased proportion of CD34+ fibroblasts within the synovium, which exhibit a high osteogenic differentiation potential and may be central to the formation of osteochondral nodules. This abnormal differentiation appears to be regulated by complex pathways related to TGF-β signaling.¹² Collectively, these molecular and genetic findings may provide a basis for future research aimed at better understanding the pathophysiology of SC.

Ankle involvement is rare, with only ~50 cases reported. Affected joints include the tibiotalar, subtalar, calcaneocuboid, naviculocuneiform, tarsometatarsal, and metatarsophalangeal joints. SC may also occur extra-articular, complicating diagnosis due to vague symptoms.^13,14 Clinical presentation includes pain, swelling, stiffness, locking, decreased range of motion, or palpable mass. One case even linked SC of the subtalar joint to ankle instability,¹⁵ highlighting the need for a high index of suspicion, especially in patients with repetitive trauma or ligamentous injury.¹⁶

Radiographs detect calcified nodules in 75–95% of cases.^17,18 These nodules are typically round, smooth, and uniform in size.¹⁷ When calcification is absent, radiographs may only show soft tissue swelling.¹⁸ CT is useful for visualizing both calcified and non-calcified nodules and distinguishing primary from secondary SC.¹⁷ MRI is superior for evaluating early SC and determining lesion extent, bone erosion, and marrow invasion.¹⁴

SC complications include recurrence and potential malignant transformation to chondrosarcoma. Recurrence rates vary from 11% to 37%, while malignant transformation occurs in ~5% of cases. The risk increases with repeated recurrence.¹⁹ Among the 48 ankle SC cases we reviewed, recurrence occurred in only two: Isbell et al reported recurrence at 2 years, managed with repeat arthroscopy, and Gatt et al described recurrence at 9 months following open excision without documented synovectomy, ultimately managed conservatively.^20,21 Al Farii et al also reported a single recurrence at 10 years among 22 cases.²² No malignant transformations of ankle SC were found in our sample. However, Galat et al reported malignant transformation in 2 of 8 foot and ankle SC cases,¹³ indicating this remains a potential concern.

Arthroscopy versus Arthrotomy

Traditionally, ankle SC has been managed through open arthrotomy with excision of loose bodies and, in some cases, synovectomy. This approach often necessitates postoperative immobilization.²³ However, advances in minimally invasive surgery over the past two decades have facilitated arthroscopic treatment, which offers reduced morbidity, faster recovery, and greater patient satisfaction.^23,24

Our literature review identified 33 cases managed arthroscopically and 11 cases treated with open arthrotomy (Table 1). Recurrence was reported in two open cases: one by Isbell et al at 2 years post-op, and another by Gatt et al at 9 months.^20,21 No recurrence was noted in the arthroscopically treated cases.

Table 1 Case Reports Listed in the Literature Including Method of Surgical Removal (Arthroscopy vs Arthrotomy), Whether Synovectomy Was Performed, Histopathological Staging Based on the Miller Classification, and Complications

While these findings suggest a potential advantage for arthroscopic treatment, the sample size is limited, and outcomes depend heavily on surgical expertise, disease stage, and joint involvement. Ultimately, no technique has been definitively proven superior. Nevertheless, arthroscopy is associated with less pain, lower infection rates, shorter hospital stays, and faster return to function, making it a favorable option when feasible.²⁴

Synovectomy versus No Synovectomy

Among the reviewed literature, 17 studies explicitly stated whether synovectomy was performed (Table 1). Of the 35 patients who underwent either partial or total synovectomy, one experienced recurrence at two years. Similarly, among the 9 patients who did not undergo synovectomy, one recurrence was reported at 9 months.^20,21

Although this sample is too small to draw statistically significant conclusions, some authors advocate synovectomy in cases with active synovitis to reduce recurrence and postoperative pain.¹⁸ Based on our findings, while synovectomy may be beneficial in selected cases, further comparative studies are needed to determine its definitive role in surgical management of SC.

Conclusion

Both arthroscopic and open surgical approaches are effective for treating ankle synovial chondromatosis. While no approach has shown definitive superiority in recurrence prevention, recent papers favor arthroscopic management due to potentially lower morbidity, faster rehabilitation, and greater patient satisfaction.^23,24

The role of synovectomy remains debated. Some evidence suggests that it may reduce recurrence in patients with active synovitis, but current data are insufficient to recommend routine use in all cases.²¹ Furthermore, while malignant transformation is rare, it underscores the need for timely diagnosis and long-term surveillance.^13,19

This case report contributes to the existing body of literature that supports functional recovery at one year post-operatively, in terms of symptoms and quality of life. Further high-quality, longitudinal studies are warranted to clarify optimal surgical techniques, the utility of synovectomy, and risk factors for malignant transformation.