The objective of this study was to define the Os Submedialis Malleolare (OSM) as an any ossicles below medial malleolus of tibia and to determine the characteristics of clinical and radiological characteristics and to evaluate results of surgical treatment of OSM.

Twenty-six patients with OSM were identified between November 1, 1998 and June 30, 2002.

The mean age was 18.3 years. All patient except one were male and soccer players comprised 71% (20 cases). Associated disease were 8 cases (29%) of chronic ankle instabilities, one case (4%) of anterior impingement syndrome and one (4%) of plantar fascitis. The most common clinical symptom was pain during walking and sports activity and sign was tenderness around medial malleolus. Only simple radiograph could reveal presence of ossicle and differentiate with acute fracture. If symptom and sign obscured , Bone scan (7 cases) and MRI (3 cases) identify causes of pain and tenderness. As a surgical treatment, all bony fragment caused symptom and sign were eliminated and medial collateral ligament was reattached meticulously. Associated chronic ankle instability were present, modified Brostrom procedure was done simultaneously. On follow-up, The symptomatic pain were wholly disappeared at average 2.2 months (1-6 months) after operation. On one year follow-up, all patients have been daily life without any complaints and all soccer players go back to the game within three months.

Os Submedialis Malleolare have relatively rare incidence and most common clinical symptom and sign is tenderness on medial malleolar area of ankle, can be diagnosed both physical examination and plain X-ray film. As a treatment, Removal of ossicle and meticulous repair or reattachment of deltoid ligament could obtain excellent or good results.