Ankle synovitis is a condition characterized by inflammation of the soft tissue lining the ankle joint capsule, known as the synovium, with subsequent ankle swelling, pain and stiffness.

The lower leg comprises of 2 long bones, known as the fibula and the tibia, which are situated beside each other (figure 1). These bones join with each other and the talus to form the ankle joint (figure 1). The ankle joint comprises of strong connective tissue surrounding the joint known as the joint capsule. The joint capsule is lined with specialized tissue known as the synovium (or synovial membrane) which is responsible for secreting lubricating fluid (synovial fluid) into the ankle joint, therefore reducing friction during ankle movements.

Following an ankle injury, swelling may accumulate within the ankle joint. This may place pressure on the synovium particularly when combined with excessive weight bearing activity and ankle movements. This may irritate the synovium causing it to become inflamed. In addition, the synovium may become inflamed directly due to injury. When the synovium becomes inflamed, the condition is known as ankle synovitis.