The muscles that extend from the back of the knee to the heel are known as the calf muscles. Among them, the gastrocnemius muscle originates behind the knee and comprises the prominent bulk of the calf. Just beneath it lies the soleus muscle, which initiates at the back of the tibia (shin). These two muscles merge to form the Achilles tendon, which attaches them to the heel. The contraction of the calf muscles plays a crucial role in raising the heel and is vital for activities such as walking, running, and jumping.