The ankle joint is formed by three bones of the leg. The tibia, the largest of the three bones, forms the roof and inner aspects of the ankle joint. Part of the tibia that forms the medial side of the ankle joint is called the medial malleolus. The fibula, or smaller leg bone, forms the lateral portion of the ankle joint. The expansion at the base of the fibula, which forms the lateral side of the ankle joint, is called the lateral malleolus. The talus is the bone that sits on the bottom portion of the joint and allows the foot to move up and down. The deltoid ligament and spring ligament stabilize the medial side of the ankle. The ATFL (Anterior Talofibular Ligament), CFL (Calcaneofibular Ligament) and PTFL (Posterior Talofibular Ligament) stabilize the lateral side of the ankle. The syndesmotic ligaments stabilize the tibia and fibular bones. An ankle sprain is an injury to one or more of these ligaments that stabilize the bones of the ankle. Chronic ankle laxity or ankle instability occurs when these ligaments fail to heal or heal stretched out.

What are the causes?

Ankle instability can result from incomplete healing of a ligament resulting from previous sprain(s) or injury to the ankle.

What are the symptoms?

Patients complain of pain with activity, recurrent sprains and a sense of instability of the ankle.

How is it diagnosed?

Your surgeon will examine both of your ankles and compare the difference in response to stress. Stress radiographs, in which the surgeon pulls on the ankle during the X-ray, will show excess forward movement of the foot in relation to the lower leg.

How is it treated?


Physical therapy to strengthen the soft tissues that support the ankle may be effective. Your surgeon may recommend a brace to help stabilize the ankle during physical activity. A cast in an acute setting may be used to immobilize the ankle and allow the injured ligaments to heal.


Patients who have continued instability despite non-operative treatment may be candidates for surgical intervention. A variety of surgical techniques are used to amend lateral or medial ankle instability. If patients do not have any healthy lateral or medial ligament tissue to repair, a lateral or medial ankle reconstruction will be performed. Tunnels are drilled in the bones where the injured ligaments normally attach and a graft is passed through the tunnels and secured. A cast is applied for 6 weeks or more to protect the reconstructive repair.