Hip iSAWE 16

Question

A 42 year old man has a year of mechanical hip pain with intermittent catching.

Hip iSAWE 16, AP radiograph of the hip
AP radiograph of the hip. Image by Ruiz Santiago, Fernando, Santiago Chinchilla, Alicia, Ansari, Afshin, Guzmán Álvarez, Luis, Castellano García, Maria del Mar, Martínez Martínez, Alberto, Tercedor Sánchez, Juan, Wikimedia Commons, CC BY 4.0.
  1. Describe the radiograph and give the diagnosis.
  2. What are the pathology and differential diagnosis?
  3. How is it treated?

Answer

Radiograph

  • Multiple small, rounded, calcified loose bodies around the hip
  • Similar size and shape
  • Possible extrinsic erosion of the femoral neck
  • Primary synovial chondromatosis

Pathology

  • Synovial metaplasia producing cartilaginous nodules
  • Nodules detach and calcify, may enlarge in synovial fluid
  • Recurrent FN1 and ACVR2A gene fusions suggest a neoplastic process
  • Milgram stages, intrasynovial active, transitional, multiple loose bodies with quiescent synovium
  • Malignant change to chondrosarcoma is rare (under 5%)

Differential diagnosis

  • Secondary osteochondromatosis from osteoarthritis (fewer, varied loose bodies)
  • Pigmented villonodular synovitis
  • Synovial chondrosarcoma

Treatment

  • Loose body removal and synovectomy
  • Arthroscopic or open with surgical dislocation
  • Recurrence 10 to 20%
  • THA for established arthritis

Related pages

Author Contributions

Orthofracs team

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.