A 19-year-old male came with chronic (for approximately 7 years) progressive palpable painless stiff swelling over the anterior aspect of the ankle with mild restriction of movements. He was ordered for an x-ray and, thereafter, an MRI with complementary ultrasound.
On radiograph (Figure 1), a soft tissue swelling was noted in the anterior aspect of the tibiotalar joint, with multiple small loose calcified bodies with preserved tibiotalar joint space and underlying bones.
On ultrasound grey scale B-mode (Figures 2 and 3), a heterogeneous echogenicity lobulated cystic lesion with multiple intralesional variable-sized calcified loose bodies and internal echogenic content were noted. On Doppler USG, arterial and venous waveforms were noted due to an underlying inflammatory/neoplastic process.
On MRI ankle (Figures 4a, 4b and 4c), a T2/PDFS hyperintense cystic lesion is noted in soft tissue planes anterior to the tibiotalar joint with hypointense septations and hypointense intralesional loose bodies, which show blooming on MEDIC sequence suggesting calcifications.
The aetiology of extra-articular synovial chondromatosis, which is uncommon in the foot and ankle, is yet unknown. It typically affects one limb at a time, with an incidence of about one in 100,000 [3]. Most extra-articular synovial chondromatosis cases show that patients have symptoms for several years prior to a diagnosis and necessary surgery. Pain, locking, instability, and palpable bulk are typical symptoms [1].
Based on the stage of maturation, three categories were used in Milgram’s 1977 description of this system: early, transitional, and late. Active synovial disease without loose bodies is referred to as the early phase. Synovial illness and loose bodies are indicative of the transitional period. Loose bodies without synovial involvement are characterised as late phases [5].
The MRI appearance of synovial chondromatosis can vary and can show loose bodies, as seen in our case, proliferative synovium, and pressure erosions, which were not seen. To differentiate highly vascular synovial tissue from synovial fluid, intravenous contrast is useful. Additionally, calcification-related regions of signal void on all pulse sequences are frequently seen on MRIs [6–8]. Since both conditions exhibit signal voids on MRI, synovial chondromatosis and pigmented villonodular synovitis might be confused with one another. However, because haemosiderin deposits are present in pigmented villonodular synovitis, the synovial lining usually exhibits a low MRI signal [6,9]. When it comes to identifying calcified loose bodies resulting from primary synovial chondromatosis, and differentiating them from more localised loose bodies related to degenerative osteoarthritis (OA), CT imaging can be helpful.
Before a complete excision, the surgical technique can be determined with the use of histologic investigation, performed by biopsy and/or surgical frozen section.
According to reports, there may be a 5% relative risk of malignant transformation in synovial chondromatosis. It is unknown if the risk of malignant degeneration is the same for extra-articular and intra-articular forms. Recurrence rates have been reported to range from 37.5% to over 50%; however, insufficient resection or incorrect diagnosis may have influenced these rates [2]. Due to prompt diagnosis and treatment, the patient has been able to resume an active and regular lifestyle without any signs of cancerous growth or recurrence.
For the purpose of treating extra-articular synovial chondromatosis, en bloc, total surgical excision is usually used. Recurrence is very rare and is ascribed to inadequate excision. Adjuvant radiation therapy or chemotherapy, whether preoperative or postoperative, is not currently indicated in light of the benign histology. Depending on institutional procedures, treatment consists of adjuvant chemotherapy and/or radiation and larger surgical resection if malignant characteristics are discovered during surgical pathologic examination [2–4,10].
Extra-articular synovial chondromatosis
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This patient is a 19-year-old male who has had a gradually developing, palpable, painless hard mass in the anterior aspect of the ankle for about 7 years, accompanied by mild limitation in range of motion. Based on the provided X-ray, ultrasound, and MRI images, the following key features are noted:
Based on imaging findings and the patient’s clinical presentation, the primary differential diagnoses include:
Taking into account the patient’s young age, the long-term slow-growing palpable mass in the anterior ankle region, and radiologic findings of multiple calcifications or cartilaginous densities with MRI evidence of synovial proliferation and nodular signals, the diagnosis most consistent with these findings is Extra-articular Synovial Chondromatosis. If there remain any clinical uncertainties, a biopsy is recommended for definitive histopathological confirmation.
Postoperative rehabilitation should follow a gradual progression based on joint range of motion, soft tissue healing status, and individual tolerance, in accordance with the FITT-VP principles:
Given the patient’s young age, if bone quality and joint condition permit, running, jumping, and other activities may be resumed in later stages of rehabilitation. Ensure that the surgical site is stable and pain-free, ideally under the guidance of a rehabilitation therapist or physician.
Disclaimer: This report is based solely on the currently available imaging and clinical information for reference purposes and cannot replace an in-person consultation or professional physician’s examination and diagnosis. If you have any questions or if your condition changes, please seek medical attention promptly.
Extra-articular synovial chondromatosis
