Primary synovial chondromatosis
Primary synovial chondromatosis, also known as Reichel syndrome, is a benign mono-articular disorder of unknown origin that is characterised by synovial metaplasia and proliferation resulting in multiple intra-articular cartilaginous loose bodies of relatively similar size, not all of which are ossified. Hence, the term synovial chondromatosis is preferred over primary synovial osteochondromatosis. It is distinct from secondary synovial chondromatosis that is the result of a degenerative change in the joint.
The age range of affected patients is wide, but most present in the 4th or 5th decades of life 2. Men are affected more frequently (M:F ratio of 2:1 to 4:1) 1,6.
Patients usually present with pain, swelling, and limitation of motion, which often progress slowly for several years. Joint effusions are common as there is a restricted range of motion.
Primary synovial chondromatosis is a self-limiting benign neoplastic process 5 characterised by proliferative chondroid nodules of the synovium. Three phases of articular disease have been identified:
- initial phase: metaplastic formation of cartilaginous nodules in the synovium
- transitional phase: detachment of those nodules and formation of free intra-articular bodies
- inactive phase: resolution of synovial proliferation, but loose bodies remain in the joint, and may increase in size obtaining nourishment from the joint fluid by diffusion
Usually, the condition is monoarticular affecting any joint but the large joints are preferentially affected:
- knee (up to 70%) 4
- hip (20%)
Occasionally, bursa or tendon sheaths may be involved 1-2.
Macroscopic appearance is that of a multi-lobulated synovium with multiple white/bluish nodules that are composed of hyaline cartilage attached to the synovium. These nodules may detach to form loose bodies. Most nodules are small (less than 2-3 cm) and usually uniform in size. Cases of massive nodules have been reported, with multiple nodules coalescing into giant nodules measuring up to 20 cm in size 5.
Microscopically the metaplastic synovium demonstrates cartilaginous nodules beneath the surface lining of the synovial membrane. They are characterised by proliferation and metaplastic transformation of the synovium, with formation of multiple cartilaginous or osteocartilaginous nodules within the joints, bursae, or tendon sheaths. These nodules are highly cellular, and the moderate pleomorphism may be identified. Cartilaginous bodies may contain cartilage alone, cartilage and bone, or mature bone with fatty marrow.
Imaging findings depend on the stage of disease and the extent of calcification or ossification of the cartilaginous nodules. In its most distinctive appearance, multiple small, well-defined, juxta-articular nodules of uniform size are observed.
Radiograph and CT
The radiographic features depend on the degree of ossification that has occurred. When calcification is absent (25-30% of cases) plain radiographs may be normal or reveal a non-specific findings, e.g. soft-tissue mass surrounding the joint, widening of the joint space, erosions of adjacent bones, or early osteoarthritic changes.
When extensive ossification is present, then many calcific joint bodies are present, either fully ossified, or demonstrating the ring and arc calcification characteristic of chondroid calcifications. They are most often multiple and of uniform size 1.
CT may be able to confirm that the loose bodies are intra-articular, and arthrography can be used as an adjunct.
MRI appearance is variable and depends on the relative preponderance of synovial proliferation, loose bodies formation, and extent of calcification or ossification.
The most frequent pattern is one of predominantly unmineralised nodules that demonstrate typical chondroid signal characteristics:
- T1: intermediate to low signal
- T2: high signal
Focal areas of signal void within these nodules represent areas of mineralisation 5.
- gradient echo (GE): will show blooming artefact 6
In some cases no mineralisation is present, and in other instances (representing 'burnt out' disease) all the nodules are fully ossified with central fat intensity in keeping with marrow.
Treatment and prognosis
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 4-5 .
Malignant degeneration into chondrosarcoma has been reported but is rare 3-4. Additionally, the cellular atypia demonstrated as synovial ostreochondromatosis may be misinterpreted in some instances as chondrosarcoma, and thus a true rate of malignant degeneration is uncertain 5.
The differential diagnosis of primary synovial chondromatosis includes:
- older age group
- extensive degenerative change
- fragments are fewer and often larger
pigmented villonodular synovitis (PVNS)
- more confluent masses
- diffuse characteristic low intensity on MRI
- synovial haemangioma
- characteristic fat signal/density
- soft tissue mass
- extension beyond the joint
- presence of metastases
- siderotic synovitis 6
- seronegative spondyloarthritides
- Jaccoud arthropathy
- juvenile idiopathic arthritis
- lyme arthritis
- rheumatoid arthritis
- systemic lupus erythematosus
- erosive osteoarthritis
- osteoarthritis (mnemonic)
- primary cystic arthrosis of the hip
- rapidly destructive osteoarthritis of the hip
- secondary synovial osteochondromatosis
- miscellaneous disorders
- related articles
- 1. Greenspan A. Orthopedic imaging, a practical approach. Lippincott Williams & Wilkins. (2004) ISBN:0781750067. Read it at Google Books - Find it at Amazon
- 2. Kiritsi O, Tsitas K, Grollios G. A case of idiopathic bursal synovial chondromatosis resembling rheumatoid arthritis. Hippokratia. 2009;13 (1): 61-3. - Free text at pubmed - Pubmed citation
- 3. Kenan S, Abdelwahab IF, Klein MJ et-al. Case report 817: Synovial chondrosarcoma secondary to synovial chondromatosis. Skeletal Radiol. 1993;22 (8): 623-6. - Pubmed citation
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- 7. Erb RE, Nance EP. Skeletal case of the day. Synovial osteochondromatosis. AJR Am J Roentgenol. 1992;158 (6): 1370-1. AJR Am J Roentgenol (citation) - Pubmed citation
- 8. Campeau NG, Lewis BD. Ultrasound appearance of synovial osteochondromatosis of the shoulder. Mayo Clin. Proc. 1998;73 (11): 1079-81. - Pubmed citation
- 7. Knoeller SM. Synovial osteochondromatosis of the hip joint. Etiology, diagnostic investigation and therapy. Acta Orthop Belg. 2001;67 (3): 201-10. Pubmed citation