Tensor Fasciae Suralis
Leg & Ankle
Most people do not have this muscle. When present, it can appear as a small lump behind the knee and may be mistaken for a Baker’s cyst, soft-tissue tumor, or other popliteal swelling.
Function
Likely weakly assists knee flexion and may help tense the fascia of the posterior leg. If it attaches into the gastrocnemius or Achilles tendon, it may have a minor assisting role in the calf/Achilles system.
Origin
Variable — may arise from semitendinosus, the long head of biceps femoris, the short head of biceps femoris, or occasionally the posterior femur/popliteal surface.
Insertion
Variable — may insert into the sural/crural fascia, the medial head of gastrocnemius, or the calcaneal/Achilles tendon.
Innervation
Usually the tibial nerve or tibial component of the sciatic nerve; rare variants may involve the common fibular (peroneal) nerve.