Calf

Anatomically, the calf corresponds to the posterior part of the leg. In simpler terms, it mainly involves the two largest muscles at the back of the leg, namely the gastrocnemius and the soleus.

Origins:

• The gastrocnemius has two heads: The lateral head originates from the back of the lateral condyle of the femur, while the medial head originates above the medial condyle of the femur.

• The soleus is a flat, sheet-like muscle located beneath the gastrocnemius. It originates from the upper parts of the tibia and fibula shafts and a tendinous arch between the two bones.

• The plantaris, sometimes considered as a vestigial part of the lateral head of the gastrocnemius, has a very small muscle belly and a long tendon that might be mistaken for a nerve. It originates from the lateral supracondylar line on the lower shaft of the femur.

Insertion:

• The calf muscles insert into the heel bone (calcaneum) through a common Achille’s tendon.

Movements/actions:

• The calf muscles facilitate flexion at the knee and ankle joints (plantar flexion). The soleus is stronger, while the gastrocnemius is faster in action. As a result, the gastrocnemius provides the primary propulsive force during walking and running, while the soleus acts as the main postural muscle.

• It’s worth noting that the calf muscles also play a vital role in circulation. Contraction of these muscles, especially the soleus, aids in venous return from the lower limb.

Innervation and blood supply:

• At the back of the knee, the sciatic nerve divides into the tibial and common fibular (common peroneal) branches. Similarly, at the lower border of the popliteus muscle, the popliteal artery and vein bifurcate into anterior and posterior tibial branches. Amongst these, the muscular branches of the tibial nerve and posterior tibial vessels serve as the primary innervation and blood supply for the calf muscles.