21 years male with a 3 years history of painful swelling around his right big toe which has gradually increased in size over the last 12 months. No preceding trauma or history of inflammatory arthritis. On examination, the swelling was tender without any skin discoloration. Range of movement was restricted.
Radiographs (Figure 1) demonstrated several mineralised densities with amorphous type of calcification in the right toe interphalangeal joint (IPJ).
MRI (Figure 2) revealed several heterogeneous low signal masses within the right IPJ on T1WI accompanied by joint effusion and adjacent bone remodelling, probably mineralised masses.
CT study (Figure 3) confirmed intra-articular calcified masses within the IPJ. Although some of the masses were connected with the cortex of the proximal phalanx no medullary continuation was evident.
Given the unusual appearances and recent interval growth, a surface based paraosseous osteosarcoma or bizarre parosteal osteochodromatous proliferation (BPOP) was suspected and an opinion from a regional bone tumour centre was sought. The patient underwent a CT guided biopsy. Histological diagnosis was primary synovial chondromatosis. Subsequently the patient had a surgical excision.
Background
Primary synovial chondromatosis
It represents an uncommon benign neoplastic process with hyaline cartilage nodules in the sub-synovial tissue of a joint, tendon sheath, or bursa. The nodules may enlarge and detach from the synovium.
It affects approximately 1 in 100,000 people.
Most commonly occur between the ages of 30-50 years.
The primary synovial chondromatosis most likely happen in the knees, hip, elbow and shoulder joints.
Secondary synovial chondromatosis (SSC)
It represents intra-articular loose bodies secondary to joint pathology such as trauma, osteoarthritis, or neuropathic osteoarthropathy.
Synovial chondromatosis can be found in different joints such as hip, shoulder, knee and elbow.
Clinical perspective
Imaging Perspective
The radiographical appearance of the synovial chondromatosis is frequently pathognomonic.
Classically, multiple chondral-osseous bodies that are similar in shape and size fill the joint space entirely and may show a ring-and-arc pattern secondary to peripheral calcification.
At the same time, joint effusion, osteopenia, and bone erosion can be present.
The MRI appearance depends on the calcification. The calcification appears as iso-hypointense on T1WI and hyperintense on T2WI. Osseous bodies present as hypointense on both T1WI and T2WI. GRE images reveal calcifications as a marked hypointensity due to the magnetic susceptibility effects. In some cases, osseous bodies may contain fatty marrow and appear hyperintense on T1WI and T2WI.CT will show soft tissue swelling and intra-articular or periarticular calcification with bony erosion.
Outcome
Treatment of synovial chondromatosis usually consists of removal of the intra-articular bodies with or without synovectomy, but local recurrence is not uncommon, occurring in ~12.5% (range 3-23%) of cases.
Take Home Message / Teaching Points
Primary synovial chondromatosis can have atypical manifestations mimicking BPOP or periosteal osteochondroma/chondroma and occasionally requires histological diagnosis.
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Primary synovial chondromatosis of the right big toe IPJ
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Based on the provided X-ray, CT, and MRI images, a relatively large soft tissue mass is observed around the metatarsophalangeal joint of the right great toe, with multiple small or clustered calcified foci displaying varying degrees of ring-shaped or arc-like calcifications. CT scans show the lesion around the joint, partially exhibiting calcification/ossification changes accompanied by mild bone erosion. On MRI, the lesion appears generally isointense to low signal on T1-weighted images, and higher signal intensities suggestive of cartilaginous components on T2-weighted images, along with low-signal calcific/ossific areas. Noticeable soft tissue swelling reduces the joint space. Overall imaging points to multiple cartilaginous lesions around the joint.
Based on multiple cartilage-like calcifications, ring-shaped or arc-like calcification patterns, and a gradually enlarging protrusion around the joint, synovial chondromatosis (primary synovial chondromatosis) is suspected. This condition more commonly affects large joints but can occasionally occur in foot joints. The disease course is often prolonged, with restricted joint motion, pain, and swelling as major clinical features.
BPOP can also present as periarticular cartilaginous proliferation and calcification, often seen as irregular new bone or cartilaginous outgrowths. However, in this case, multiple lesions appear more commonly in the joint cavity or synovium, with a three-year history of gradual enlargement. Further differentiation is needed in conjunction with pathological or histological features.
If a soft tissue mass and localized bone erosion are observed on plain films or CT, one must consider the possibility of a superficial malignant tumor. However, given the slow growth, less severe pain compared to typical malignancies, and pathological findings consistent with chondroid proliferation, the likelihood of malignancy is relatively low.
Taking into account the patient’s young age (21 years old), relatively long disease course (around three years of gradual enlargement), radiological evidence of cartilaginous lesions around the joint, multiple calcifications, restricted joint motion, and CT-guided pathological biopsy confirming Primary Synovial Chondromatosis, the most likely diagnosis is Primary Synovial Chondromatosis.
Due to localized pain, limited motion, and imaging indicating continuous growth of cartilaginous nodules, surgical removal of the loose bodies and affected synovium (synovectomy) is generally recommended. Arthroscopic or open surgery may be chosen depending on the lesion’s extent and the degree of joint involvement.
Close postoperative follow-up is necessary to monitor for local recurrence. Literature suggests a recurrence rate of about 3-23%. If significant functional impairment or new cartilaginous fragments develop, timely evaluation and management should be undertaken.
Postoperatively or during remission, an individualized rehabilitation plan should be established based on the patient's overall condition (bone strength, cartilage healing status, range of motion, pain level, etc.). The following strategies are recommended:
· Focus on pain relief, reducing swelling, and preventing joint stiffness. Perform gentle passive joint exercises (e.g., gentle movement of the ankle and toe joints) and basic strengthening exercises with low intensity, high frequency, and short duration to avoid exacerbating pain.
· Recommend 2-3 sessions per day, each lasting 5-10 minutes, with passive or assisted active training. Use ice packs or physical therapy to reduce swelling and pain.
· As joint pain subsides, gradually introduce active joint movement and resistance training. Light resistance with elastic bands or simple equipment can help restore and strengthen foot and lower-leg muscles, stabilizing the joint.
· Exercise frequency of 3-5 times per week for 20-30 minutes each session at a moderately low intensity is suggested (avoiding significant pain or swelling).
· After restoring basic joint range of motion and muscle strength, prioritize proprioception training and weight-bearing exercises (e.g., single-leg stance, light tiptoe drills), gradually progressing to walking or light jogging if cleared by a physician.
· Increase exercise frequency to 4-5 times per week, with sessions longer than 30 minutes. Intensity and duration should be increased progressively based on tolerance. If any activity causes significant pain or discomfort, adjust or pause the exercise and seek medical advice.
· If the patient has other joint pathologies, low bone density, or chronic diseases, more conservative exercises should be conducted under professional supervision.
· Adhere strictly to the “pain-free or minimal pain” principle, increasing joint load gradually while closely monitoring soft tissue and joint responses.
Disclaimer: This report is based on the provided medical history and imaging data for reference and cannot replace in-person consultation or professional medical advice. If the patient has any concerns, they should seek medical attention promptly and follow specialist guidance and treatment.
Primary synovial chondromatosis of the right big toe IPJ
