The insertion of the biceps femoris is on which structure?

• A. Head of fibula
• B. Calcaneus via calcaneal tendon
• C. Proximal medial shaft of tibia
• D. Posterior aspect of medial tibial condyle

Answer: (A)

Where the distal tendon of the biceps femoris attaches determines its action. This muscle, with its two heads, converges to insert on the head of the fibula. That placement on the fibular head allows knee flexion and, when the knee is bent, lateral rotation of the leg. The other options point to attachments for different structures: the calcaneus via the calcaneal tendon is where the gastrocnemius and soleus attach (not the hamstrings); the proximal medial shaft of the tibia is a common insertion for muscles that form the pes anserinus (such as semitendinosus and gracilis); and the posterior aspect of the medial tibial condyle is where the semimembranosus inserts. So the head of the fibula is the correct insertion site.