Synovial chondromatosis is a rare condition characterized by benign, proliferative cartilaginous lesions that arise from the synovial tissue, tenosynovium, or bursal lining of/or near joints. Although synovial chondromatosis can be found all over the body, the condition most commonly affects large joints like the knees, elbows, ankles, hips, and shoulders. However, it also may involve the wrist, metacarpophalangeal (MP), or interphalangeal (IP) joints. The condition is also usually monoarticular, but more than one joint may be affected in some cases. Patients that only present with mild symptoms may be effectively managed with careful observation and some conservative interventions, but resection of loose bodies with or without synovectomy is generally typically needed for cases of primary synovial chondromatosis with debilitating symptoms.1-5
Pathophysiology
- Primary synovial chondromatosis was believed to result from a benign reactive metaplasia of synovial tissue into cartilaginous tissue, arising either from the articular synovium or the tendon sheath synovium; however, increasing evidence has suggested that it may actually be a neoplastic condition.1,3
- There are reports of its malignant transformation into chondrosarcoma and evidence of involved chondrocytes, demonstrating atypical cytology and architecture on histology.1
- Multiple cytogenetic abnormalities have also been reported, such as 1p13, 1p21–22, 12q13–15, and +5, and a murine model with a hedgehog signaling mutation has shown an increased incidence of synovial chondromatosis.1
- Synovial chondromatosis commonly progresses gradually, although spontaneous regression also has been reported.1
- A commonly used classification system was created by Milgram and categorizes it into the following 3 phases:
- Early phase: no loose bodies are present, but active intrasynovial disease exists
- Transitional phase: loose bodies are present with active intrasynovial disease
- Late phase: multiple loose bodies are present without active intrasynovial disease3,4
- Synovial chondromatosis can be further subdivided into either primary or secondary, and either synovial or tenosynovial:
- Primary: cartilaginous tissue arising directly from metaplastic synovial tissue, tenosynovium, or bursal lining
- Secondary: loose bodies arising from hyaline cartilage implanted into the joint space or tendon sheath from degenerative joint disease, trauma, or neuropathic arthropathy
- Synovial (intra-articular) chondromatosis: more common and usually monoarticular, unless associated with a familial chondromatosis or conditions such as Wagner-Stickler syndrome
- Tenosynovial (extra-articular) chondromatosis: most common over the flexor tendons in the fingers but can be found along any tendinous sheath1
Related Anatomy
- MP joint
- IP joint
- Radiolunar joint
- Synovial tissue
- Cartilaginous tissue
- Tenosynovium
- Bursa
- Tendon sheath
Incidence and Related Conditions
- The exact incidence of synovial chondromatosis is ill-defined and probably less than currently estimated, likely due to confusion with the much more prevalent secondary chondromatosis or soft tissue chondroma.1
- Synovial chondromatosis can occur at any age, but usually presents between ages 20-50 years.1,6
- No sex predilection has been established, but some studies suggest that it is twice as common in men versus women.1,3,6
- Malignant transformation of synovial chondromatosis into chondrosarcoma was considered extremely rare, but one study reported a 5% relative risk. The reported recurrence rate for synovial chondromatosis also varies widely, with reports ranging from 3-60%.1
- The most common site of synovial chondromatosis is the large joints, predominantly the knee (~40%), hip, and shoulder.4
- It rarely affects the wrist, MP, and IP joints, with very few cases reported. Tenosynovial chondromatosis, however, is most often found in the flexor tendons of the hand.1,3,7
Differential Diagnosis
- Secondary chondromatosis
- Chondrosarcoma
- Soft tissue chondroma
- Periosteal chondroma
- Tenosynovial giant cell tumor
- Calcifying aponeurotic fibroma
- Tumoral calcinosis
- Hydroxyapatite deposition disease
- Foreign body
- Inflammatory arthritides
- Osteoarthritis
- Osteochondritis dissecans
- Osteochondral fracture
- Neuropathic joint
- Tuberculosis
- Rheumatoid arthritis
- Monoarticular synovitis
- Synovial sarcoma
- Villonodular synovitis
- Hemangioma
- Dermatomyositis
- Hyperparathyroidism
