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Synovial chondromatosis


  • Also known as synovial chondro-metaplasia
  • Rare condition of unclear etiology in which foci of cartilage develop in the synovial membrane of joints, bursae, or tendon sheaths as a result of metaplasia of the subsynovial connective tissue
  • Nodules can detach and become loose bodies within the joint, which may undergo secondary calcification and ossification
  • Extra-articular involvement may occur if proliferating loose bodies break through joint capsule or if synovial structures outside joint (eg, tendon sheaths, bursae) are involved
  • Generally a primary condition, but may occur secondary to osteoarthritis
  • Most often arises in weight-bearing joints of the lower extremity (hip, knee); usually monoarticular involvement
  • In upper extremity, shoulder, elbow, wrist, and small joints of hand may be affected

Tumor biology and incidence

  • Benign periarticular cartilaginous lesions
  • May be calcified and/or ossified
  • Not known to metastasize but may give rise to intra-articular loose bodies
  • Extremely low risk of malignant transformation to chondrosarcoma


Primarily adults in their 20s through 40s


M:F = 2:1


  • Joint pain, swelling, stiffness
  • Patient may report history of slowly progressing symptoms: clicking, locking, or catching sensation during joint range of motion
  • Baseline dull, aching discomfort exacerbated by motion, causing sharp pain

Physical findings

  • Locked joint or limited range of motion (10-15 degree loss of flexion/extension)
  • Joint effusion
  • Possible inflammatory signs
  • Compare to contralateral side, noting fullness, effusion, palpable loose bodies in synvovial recesses, and medial/lateral joint line tenderness

Plain films

  • Knee most commonly involved
  • Hip, shoulder, elbow, and ankle also involved
  • May affect any joint bursa or tendon sheath
  • Multiple calcified bodies in joint; regular in outline and uniform in size
  • Range from a few millimeters to several centimeters.
Tumor effect on bone
  • Some individual lesions may extrinsically erode underlying surface of bone and articular cartilage
  • May progress to cause degenerative arthritis
Bone response to tumor

Mild reactive sclerosis may result from bone erosion

  • Lesions composed of cartilage matrix
  • Variable degrees of calcification and/or ossification

Not applicable

Soft tissue mass

Lesions frequently extend into bursae around distended joints

CT scan

CT scan can demonstrate an effusion, a mass effect with radiolucent loose bodies, or multiple calcified and or ossified loose bodies


  • Variable findings depending on relative amounts of synovial proliferation and calcified nodule formation
  • Loose bodies tend to have low signal on T1-weighted images and high signal on T2-weighted images
  • Lesions with extensive calcification may have low signal on all images

Classification (Milgram)

  • Early: Chondrometaplasia but no loose bodies
  • Transitional: Synovial disease and loose bodies
  • Late: Loose bodies predominate generally with extensive effusion

Differential diagnosis

  • Any source of loose bodies (secondary osteochondromatosis), such as osteochondral fracture, osteoarthritis, neuropathic joint, or osteochondritis dissecans
  • Synovial chondrosarcoma
  • Myositis ossificans
  • Pigmented villonodular synovitis
  • Septic joint
  • Calcific tendonitis (shoulder)
  • Soft tissue chondroma (hand),
  • Saponification of patellar fat pad (anterior knee)
  • Osteogenic sarcoma
  • Myxoid chondrosarcoma (posterior knee)

Natural history

  • Generally benign, self limiting disease
  • However, can become disabling, resulting in secondary degenerative osteoarthritis


  • Gross: Thickened, nodular synovium often with separate loose bodies of chondroid-appearing tissue
  • Microscopic: Nodules of chondroid tissue within synovium
  • Cartilage may be cellular but cells are in clusters
  • May be variable mineralization
  • Differentiation into trabecular bone may be present

Diagnosis and treatment

  • Diagnosis may be made radiographically
    • Plain radiographs may be normal and may require further investigations – such as arthrogram, MRI, or arthroscopy – to make diagnosis
  • Treatment is controversial
    • Removal of loose bodies can be done with or without total synovectomy
      • Alleviates symptoms and prevents secondary joint changes
      • Low risk of recurrence (<20%).
    • Some clinicians prefer complete synovectomy
      • More extensive than removal of loose bodies
      • May be associated with increased morbidity (eg, arthrofibrosis)
      • May have lower recurrence rate than removal of loose bodies

Surgical findings


  • Recurrence
  • Loss of range of motion
  • Arthrofibrosis
  • Arthritis
  • Transition to synovial chondrosarcoma (rare/associated with multiple recurrences)

Recommended reading

OKU Musculoskeletal Tumors AAOS 2nd Edition 2007, Ch 28 pg 265-266.

Adelani et al. Benign Synovial Disorders. JAAOS, Vol 16, No 5, May 2008, 268-275

Sperling et al. Synovial chondromatosis and chondrosarcoma: a diagnostic dilemma. Sarcoma. 2003;7(2):69-73.

Maurice et al.  Synvovial Chondromatosis JBJS Br 1988; 70(5): 807-11.

Sah et al. Malignant Transformation of Synovial Chondromatosis of the Shoulder to Chondrosarcoma*.* A Case Report. JBJS Jun 2007;89:1321-1328.

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