Intra-Articular Calcaneus Osteoid Osteoma With an Ankle Varus and a Red-Brown Synovial Fluid in the Affected Joint, a Case Report.

It is still essential that intra-articular calcaneal osteoid osteoma should be considered in patients with prolonged pain and varus of the ankle. The red-brown synovial may be used as a finding for diagnosis.