IS Case 380: Synovial osteochondromatosis

Keith Forrest Dockery, MD

2009 URMC Imaging Sciences
Publication Date: 2010-03-02


Patient is a 65-year-old mentally retarded, institutionalized, debilitated female with multiple medical problems, undergoing acute hospitalization for peritonitis, pneumatosis, and megacolon. She is status post-exploratory laparotomy, with subtotal colectomy and ileostomy, now presenting from intensive care with incidental finding on radiograph. Inpatient exam reveals extremities with no edema, but contraction and wasting are evident.


AP portable chest demonstrated numerous, peri-articular well-circumscribed calcificied bodies measuring more than 1 cm each in the right shoulder. (Other findings pertaining to acute hospitalization are not considered germane to the case discussion.)


The patient has typical findings of synovial osteochondromatosis on plain radiograph. Her debility and mental retardation probably account for her lack of reported symptoms. A review of prior clinical admission notes did not reveal a diagnosis of synovial chondromatosis. A right shoulder radiograph from 9 years prior (for question of bleed or fracture) indicates calcific densities of the shoulder capsule, with severe degenerative changes, but no fracture. Similar findings are reported on a chest film 11 years ago. This would support that the right shoulder disease is a longstanding process (images are no longer extant).

Pathophysiology: Synovial chondromatosis is a metaplastic synovial disease characterized by hyperplasia nodular proliferation of the synovium with fragmentation into the joint space. Fragments frequently calcify or ossify. Disease is typically mono-articular. The most often affected joint is the knee in 60-70% of cases; next most common are the shoulder, elbow, and hip, followed by other joints. Disease may affect any synovial joint or bursa. Multi-articular disease is reported. Ossified fragments may become centimeters in size, and usually number more than five. Malignant transformation is extremely rare.

Two etiologies are suggested: (1) Primary type - ectopic synovium with subsequent loose body formation; (2) Secondary type – fragments of synovium and loose bodies form secondary to trauma or underlying degenerative joint diseases.

The primary synovial chondromatosis develops in 3 phases, (per Milgram 1977 [4]): Phase 1 – Intrasynovial Involvement (Early): Active intrasynovial disease without loose bodies. Time course is weeks to months.

Phase 2 – Intrasynovial Involvement and Free Bodies (Transitional): Transitional lesions with osteochondral nodules in the synovial membrane and osteochondral bodies lying free in the joint cavity. Time course is weeks to years.

Phase 3 – Multiple Free Bodies Due to Synovial Osteochondromatosis (Late): Osteochondral bodies with quiescent intrasynovial disease. Time course is months to years.

Demographics: Male to female predominance, approximately 2:1. Age of onset usually occurs in the third through fifth decade.

Imaging: Plain radiograph is usually sufficient, but MR is helpful, in diagnosis of non-calcified forms and showing extent of disease. Computed tomography may be utilized with or without CT arthrography. Ultrasound has been used. Tc-99m MDP nuclear medicine bone scans have also been used.

On plain radiograph, fragments are usually > 5 mm. Pressure erosions can be seen in adjacent bone, a.k.a. saucerization. On MR, T1-weighted images would show iso- to hyp-intense rounded, intra-articular fragments: fragments may extend into the peri-articular soft-tissue. T2-weighted images would show hyper-intense signal in the synovial membrane and effusion. Increasing calcification results in corresponding focal hypo-intensity.

Differential Diagnosis: The differential diagnosis is typically short, including: pigmented villonodular synovitis; rice bodies of tuberculosis; rheumatoid arthritis; chondromas. Note that secondary degenerative changes may occur.

Treatment: Treatment is complete synovectomy with loose body removal. The disease can recur in up to 25% of cases as total synovectomy is rarely attained at surgery.

Conclusion: Given this patient’s debility and mental retardation, her history and symptomatology are difficult to assess. She could be classified as a Phase III primary versus secondary type synovial osteochondromatosis, viz., the etiology could be idiopathic or be sequela of chronic trauma or osteoarthritis. Other co-morbidities exclude this patient from definitive surgery.


  1. Greenspan A. Orthopedic Radiology: A Practical Approach. 3rd Ed., Lippincott, Williams, and Wilkins. Philidelphia, 2000.
  2. Monu JU, Oka M. Synovial Osteochondromatosis. eMedicine. Jun 21, 2007. (An extensive reference list is available in this article.)
  3. Duke Orthopaedics presents Wheeless' Textbook of Orthopaedics. Synovial Chondromatosis.
  4. Milgram JW. Synovial osteochondromatosis: a histopathological study of thirty cases. J Bone Joint Surg Am. 1977 Sep;59(6):792-801. PMID: 908703

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