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Synovial Osteochondromatosis

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Other Names

  • Synovial Chondromatosis
  • Synovial Osteochondromatosis (SOC)
  • Primary Synovial Chondromatosis
  • Primary Synovial Osteochondromatosis
  • Synovial Chondrometaplasia
  • Reichel Syndrome


  • This page refers to Synovial Chondromatosis (SOC), a rare proliferative disease of the synovium associated with cartilage metaplasia that results in multiple intra-articular loose bodies.


  • First described in 1558 in the knee by Ambrose (need citation)
  • In 1813, Laennac described intra-articular loose bodies arising from subsynovial tissues (need citation)
  • First termed Synovial Osteochondromatosis in 1958[1]


  • Incidence
    • One study reported approximately 1 in 100,000[2]
    • In England, estimated to be 1.8 per million individuals[3]
  • Usually affects young adults, age 30 to 50[4]
  • Usually unilateral, bilateral in about 5% to 10% of cases[5]


Synovial osteochodromatosis of the elbow and ankle[6]
A thirty-two-year-old man with malignant transformation of SOC of the right shoulder into chondrosarcoma[7]


  • Rare proliferation of cartilage within the synovium
  • Results in intra-articular loose bodies, less commonly in tendon sheaths and bursae
  • Mild disease is may be non surgical while more significant symptoms require surgery


  • Commonly affects diarthrodial weight bearing joints
  • Knee is most commonly affected (~50% to 70%)
  • Followed by other large joints including hip (20%), elbow, and shoulder
  • It has also been reported in the ankle, wrist and other smaller joints


  • Often delayed
  • Average time from symptom onset to diagnosis of 5 years (need citation)


  • General
    • Unknown
    • Debate as to whether it is metaplastic or benign neoplastic disease
  • Benign neoplastic disease currently favored as etiology of SOC[8]
  • Mechanism
    • Associated with cartilage metaplasia within the synovial membrane
    • Metaplastic synovium organizes into nodules
    • Progressive enlargement and ossification occur with time
    • If not treated, growth continues and they become larger, more calcified
    • Results in multiple intra-articular loose bodies
    • Ranges from synovial tissue to firm nodules of cartilage

Risk Factors

  • Demographic
    • 2:1 Male to female ratio (need citation)
  • Genetic
    • Chromosome 6 abnormalities[9]

Differential Diagnosis

  • Trauma-related:
    • Fracture with avulsed fragment
    • Fragmentation of meniscus with calcification
  • Degenerative joint disease related
    • Degenerative joint disease with detached spur
  • Synovial proliferation:
    • Pigmented villonodular synovitis
  • Neoplastic:
    • Synovial chondrosarcoma
  • Other:
  • Inflammatory Arthropathy

Clinical Features


  • History of SOC is non specific
  • Patients may be asymptomatic
  • Slow, chronic progression of symptoms
  • Pain and swelling
  • Pain worse with activity
  • Mechanical symptoms including stiffness, clicking, grating, locking
  • Can occur in the bursa overlying an osteochondroma

Physical Exam

  • Decreased range of motion
  • Can have warmth, erythema, or tenderness
  • Joint effusion is often present
  • Palpable masses can occur


Primary synovial osteochondromatosis
Preoperative lateral radiograph showing a large intra-articular mass with cortical destruction and small, calcified nodules. Preoperative T2-weighted lateral MRI scan showing large intra-articular chondral nodules that have coalesced, consistent with tumefactive SOC.[7]
Gross pathology of the xray and MRI above[7]
Synovial Osteochondromatosis of the hand[10]
Synovial Osteochondromatosis of the knee[11]


  • Recommended initial imaging modality
    • Abnormal in 70% of cases[12]
  • Findings[13]
    • Multiple, smooth, oval-shaped calcified masses within the joint space or bursa
    • Characteristic "pop corn appearance", typically evenly distributed
    • Variable depending on stage of disease
    • May show stippled calcification
    • Serial imaging may show changes in size, disappearance, migration
    • Degenerative changes, effusion are often seen
    • Periarticular erosions are seen in 30% of cases due to pressure within a tight capsule[14]


  • Early Findings
    • Initially cartilage nodules are only visible on MRI
    • Lobular appearance
    • Cartilage bodies appear isointense on T1, hyperintense on T2
  • Late Findings
    • Signal drop out consistent with calcification
  • Consider arthrogram


  • Useful early in disease process before calcification begins
  • Can detect non-calcified masses, distinguish from simple joint effusion
    • Low attenuation lesions with a lobular outline
  • Calcifications[15]
    • Optimal modality in assessing calcification
  • Inferior to MRI for the following
    • Does not show marrow invasion well
    • Chondromal nodules can be occult
    • Extent of disease better seen on MRI


  • Findings
    • Heterogenous, avascular mass surrounded by fluid
    • Nodules appear as hyperechoic foci with acoustic shadowing
    • Dynamic evaluation can identify gravity-dependent nodules


  • Gross
    • Glistening, gray-white polypoid cartilaginous or osteocartilaginous bodies
    • Typically spherical
    • Size ranges from millimeters to several centimeters
  • Microscopic Synovium
    • Villous hyperplasia, which imparts a wrinkled appearance on gross examination
    • Cartilaginous bodies may be attached attached to the synovium
    • Involvement may be focal or diffuse
    • Cartilage can be hyaline or myxoid


  • Primary
    • Occurs in an otherwise normal joint
    • Typically affects a single joint
    • Common in 3rd to 5th decade of life
  • Secondary
    • Occurs in older patients with previous joint disease (i.e. osteoarthritis)
    • Often bilateral with multiple joint involvement

Milgram Classification

  • First presented in 1977[16]
    • Based on gross and pathologic cases
    • Not widely used for clinical decision making
  • Stage I
    • Disease: active, inflammatory intrasynovial process without loose bodies
    • Symptoms: localized joint pain and swelling (or may be asymptomatic)
  • Stage II
    • Disease: active synovial proliferation with transitional loose bodies (transition from pedunculated to free)
    • Symptoms: patients often present with mechanical symptoms and decreased range of motion
  • Stage III
    • Disease: characterized by the presence of multiple loose bodies, minimal synovial disease, minimal inflammation
    • May be thought of as a quiescent stage of the disease with no ongoing metaplasia



  • Indications
    • Asymptomatic
    • Mild symptoms not affecting range of motion
  • Treatment


  • Indications
    • Severe symptoms affecting range of motion
    • Mechanical symptoms
  • Technique
    • Open or arthroscopic
    • Synovectomy, lose body resection

Rehab and Return to Play


  • No clear rehabilitation guidelines

Return to Play/ Work

  • No clear return to play guidelines

Complications and Prognosis


  • Outcomes
    • Treatment is mainly symptomatic, may help prevent degenerative changes
  • Recurrence[17][18]
    • 3-23%
    • Thought to be due to incomplete surgical resection


  • Malignant transformation into synovial chondrosarcoma
  • Mechanical symptoms
    • Clicking, grating or locking

See Also




  1. Jaffe HL (1958) Tumours and tumorous conditions of bones and joints, 1st edn. Lea & Fabiger, Philedelphia,USA, pp 558–567
  2. Felbel J, Gresser U, Lohmoller G, Zollner N (1992) Familial chondromatosis combined with dwarfism. Hum Genet 88:351–354
  3. Evans S, Boffano M, Chaudhry S, Jeys L, Grimer R. Synovial chondrosarcoma arising in synovial chondromatosis. Sarcoma. 2014;2014: 647939. Epub 2014 Mar 5.
  4. Adelani MA, Wupperman RM, Holt GE. Benign synovial disorders. J Am Acad Orthop Surg. 2008 May;16(5):268-75.
  5. Seckley J, Anderson SG, Snow TM, Benjamin M (2002) A rare case of polyarticular synovial osteochondromatosis. J Anat 200(5):524
  6. Image courtesy of https://orthoinfo.aaos.org/, "Synovial Chondromatosis"
  7. 7.0 7.1 7.2 Neumann, Julie A., et al. "Synovial chondromatosis." JBJS reviews 4.5 (2016).
  8. Robinson D, Hasharoni A, Evron Z, Segal M, Nevo Z (2000) Synovial chondromatosis: the possible role of FGF 9 and FGF receptor 3 in its pathology. Int J Exp Pathol 81:183–189
  9. Buddingh EP, Krallman P, Neff JR, NelsonM, Liu J, Bridge JA. Chromosome 6 abnormalities are recurrent in synovial chondromatosis. Cancer Genet Cytogenet. 2003 Jan 1;140(1): 18-22.
  10. Case courtesy of Dr Maulik S Patel, Radiopaedia.org, rID: 23031
  11. Terazaki, Carlos Renato Ticianelli, et al. "Synovial chondromatosis of the shoulder: imaging findings." Radiologia Brasileira 47 (2014): 38-42.
  12. Mohana-Borges AV, Chung CB, Resnick D (2004) Monoarticular arthritis. Radiol Clin North Am 42 (1):135–149
  13. Alexander JE, Holder JC, McConnell JR, Fontenot E Jr. Synovial osteochondromatosis. Am Fam Physician. 1987 Feb;35(2):157-61.
  14. Norman A, Steiner GC (1986) Bone erosion in synovial chondromatosis. Radiology 161:749–752
  15. Murphey MD, Vidal JA, Fanburg- Smith JD, Gajewski DA (2007) Imaging of Synovial Chondromatosis with Radiologic-Pathologic Correlation. RadioGraphics 27:1465–1488
  16. MilgramJW. Synovial osteochondromatosis: a histopathological study of thirty cases. JBone Joint Surg Am. 1977 Sep;59(6):792-801.
  17. Maurice H, Crone M, Watt I (1998) Synovial chondromatosis. J Bone Joint Surg Br 70:807–811
  18. Shpitzer T, Ganel A, Engelberg S (1990) Surgery for synovial chondromatosis: 26 cases followed up for 6 years. Acta Orthop Scand 61:567– 569
Created by:
John Kiel on 30 September 2022 14:42:45
Last edited:
8 January 2024 01:47:15