The superficial muscles of back of leg:
Gastrocnemius: medial and lateral heads from the posterior aspect of the femur just above the condyles.
Soleus is deep to the gastrocnemius: from the proximal 1/3 of the fibula, soleal line of tibia, and fibrous arch across the popliteal vessels near their bifurcation.
The muscles unite to form the tendo calcaneus, which is inserted into the calcaneum. Shortening of these muscles strains the tendo calcaneus and causes Achilles tendonitis.

Release the soleus and gastrocnemii muscles. When pain is bilateral, treat one side at a time only as soreness from needling can cause limping.

Other Pains in the foot may result from:

Shortening of the extensor hallucis longus and extensor digitorum longus muscles which dorsiflex the toes, thus angulating the metatarso-phalangeal joint and exposing the tender underside of the heads of metatarsals and plantar nerves to pressure on walking.
Metatarsalgia. Pain in the metatarsal region may arise from weakness of the intrinsic muscles. Palpate for tenderness in the flexor digiti minimi, abductor digiti minimi, flexor digitorum brevis, flexor hallucis brevis, abductor hallucis, and adductor hallucis muscles. Also check the flexor hallucis longus and flexor digitorum longus muscles in the calf.
Plantar (Morton’s) neuralgia. An interdigital plantar neuroma may subsequently develop in the interdigital nerves, commonly between the third and fourth toes, causing pain, numbness, tingling, aching, and burning in the distal forefoot. Treatment is to the above extensor muscles. The long flexors and lumbricals may also require treatment if tender (see below).
Plantar fasciitis is one of the most common causes of foot pain. The condition is frequently associated with systemic rheumatoid diseases, and many patients are HLA-B27 positive and have other tender muscles in the body. A hallmark for diagnosis is point tenderness along the longitudinal bands of the plantar fascia. Identify and needle the discrete points of tenderness, penetrating through to reach the flexor digitorum brevis and flexor accessorius muscles (quadratus plantae).
Calcaneal heel spur which sometimes develops from long-standing plantar fasciitis, responds to the same treatment. Direct needling of the spur is seldom necessary.