The extensor retinaculum refers to the set of ligaments inside the ankle that connect the tibia and fibula, which are the bones of the lower leg. The Achilles tendon and tissue inside the sole of the foot are also connected by the extensor retinaculum. The superior extensor retinaculum ligament extends across the back of the leg and is attached horizontally to the fibula and in the middle of the tibia.
These ligaments are a group of fibrous bands inside the fascia of the leg that attach the extensor tendons to the joint of the ankle. The inferior extensor retinaculum is the lower band of extensor retinaculum that attaches horizontally to the calcaneus (heel bone) and passes over and under the extensor muscle tendons in the ankle. The superior extensor retinaculum crosses over the front part of the ankle and binds the peroneus tertius, extensor hallucis longus, tibialis anterior, and the extensor digitorum longus tendons to the joint of the ankle.