The flexor digitorum longus muscle can cause and contribute to pain in the foot that radiates into the back of the leg. It can contribute to the development of hammertoe and claw toe.
The plantaris muscle is a very small muscle located behind the knee. It contributes to pain behind the knee and is occasionally involved in cramps in the calf.
The gastrocnemius muscle is a prime contributor to pain in the back of the knee. It can contribute to lower leg, ankle, and arch pain.
The soleus muscle can cause and contribute to pain in the heel, ankle and back of the knee. It can also cause pain in the low back on the same side of the affected leg. Dysfunction of the soleus muscle can also contribute to swelling in the foot and ankle. Occasionally a trigger point at the bottom and outside of the muscle can contribute to pain in the jaw and side of the head.
The tibialis posterior muscle can cause and contribute to pain in the lower leg just above the heel. This pain will often extend into the heel and the bottom of the foot. The pain will sometimes extend up into the lower calf. If you have fallen arches, you should check the tibialis posterior for trigger points and tightness because dysfunction of this muscle will allow your ankles to collapse inward.