Korean J Sports Med.  2018 Dec;36(4):221-226. 10.5763/kjsm.2018.36.4.221.

Synovial Osteochondromatosis of the Subtalar Joint in an Adolescent Baseball Player

  • 1Department of Orthopaedic Surgery, Good Samsun Hospital, Busan, Korea. oyong79@naver.com


Synovial chondromatosis is an uncommon disorder characterized by cartilaginous proliferation within the synovial membrane of the articular joint. Smaller joints are rarely affected and it may be progressed to osteochondromatosis after ossification or calcification of metaplastic cartilage. It is commonly presented in the third to fourth decade of life, but rarely presented in adolescence. We report a unique case of synovial osteochondromatosis of the subtalar joint in 14-year-old baseball player. Arthroscopic removal of loose body and complete excision of the osteochondral mass with concomitant synovectomy resulted in satisfactory outcome without recurrence at final follow-up.


Adolescent; Arthroscopy; Baseball player; Subtalar joint; Synovial chondromatosis

MeSH Terms

Chondromatosis, Synovial*
Follow-Up Studies
Subtalar Joint*
Synovial Membrane


  • Fig. 1 Preoperative plain radiographs of left ankle. (A) Anteroposterior view showed radio-opaque area near the subtalar joint (arrow). Mortis (B) and lateral (C) views showed innumerable subcentimeter loose bodies within posterior subtalar joint (arrows).

  • Fig. 2 Computed tomographic images of the left ankle. Multiple high-density loose bodies were demonstrated in subtalar joint space on coronal (A) and sagittal (B) images. (C, D) Three-imensional reconstruction images showed the main clusters of multiple loose bodies were in posterior subtalar joint and the remainders were scattered into sinus tarsi.

  • Fig. 3 Magnetic resonance imaging of the left ankle. (A) The T1-weighted coronal image demonstrated a lobulated low signal intensity mass (arrow). (B) T2-weighted axial image showed multiple osteochondral and chondral loose bodies which demonstrated signal void or low signal intensity (arrow) surrounded by an area of high signal intensity effusion. Low signal intensity cyst-like synovial lining (arrowheads) was extended from posterior subtalar joint on (C) T2-weighted and (D) proton density image, and signal void loose bodies were identified in sinus tarsi.

  • Fig. 4 Subtalar arthroscopic photographs through the lateral portal (A, B) and the posterolateral portal (C, D). (A) Multiple cartilaginous loose bodies (asterisks) and minimal synovial proliferation were shown around talocalcaneal interosseous ligament (IOL). After removal of loose bodies, (B) synovectomy was performed in sinus tarsi. Yellowish nodular cartilaginous metaplasia and accompanying loose bodies were shown in (C) lateral and (D) medial gutters of posterior subtalar joint. Asterisks indicate multiple loose bodies. PFC: posterior articular facet of calcaneus, L: lateral malleolus, T: talus.

  • Fig. 5 Intraoperative photographs demonstrate (A) extension of the posterolateral arthroscopic portal between lateral malleolus and Achilles tendon and (B) multiple osteochondral and chondral loose bodies in varying size.

  • Fig. 6 Histological sections of osteochondral loose bodies from the synovium of the patients, showing (A) multiple osteoid covered by fibrocartilage (H&E, ×40) and (B) vascular proliferation and osteochondral metaplasia of the synovial stroma (H&E, ×100).


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