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 flexor hallucis longus can cause and contribute to pain in the big toe and ball of the foot. A classic sign of flexor hallucis longus dysfunction is numbness on the bottom of the big toe.
The abductor hallucis muscle is located on the bottom of the foot. It can cause pain in the ankle and heel. There is a deep aching pain in the heel and ankle when trying to rest.
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.