Many people are aware of their larger, more superficial calf muscles, gastrocnemius and soleus. But what about the smaller, deeper and less known calf muscles? What is their purpose, and what are the symptoms when they aren’t functioning properly? Today I am writing specifically about tibialis posterior, flexor digitorum longus and flexor hallucis longus.
Tibialis posterior originates at the proximal, posterior shafts of the tibia and fibula (bones of lower leg) and the interosseous membrane. It inserts into all five tarsal bones (small foot bones) and bases of second through fourth metatarsals (long foot bones). It inverts the foot, plantar flexes the ankle, and helps maintain the long arch of the foot, keeping weight properly distributed to the outside of the foot.
Muscle spasm, trigger points and weakness in tibialis posterior can contribute to Achilles tendonitis, so it is wise to treat this muscle along with gastrocnemius and soleus.
Dysfunction in this muscle can give the appearance of fallen arches and can contribute to issues such as shin splints. Pain from tibialis posterior trigger points presents primarily in the Achilles tendon especially while running or walking, but can also extend to the calf, heel and sole of the foot. If you have issues with chronic heel spurs, you may explore treating this muscle, as it may be part of the problem.
Flexor digitorum longus flexes the second through fifth toes, inverts the foot, and is a weak plantar flexor of the ankle. Flexor hallucis longus performs the same actions, except that it is a flexor of the big toe instead of the other four toes. FDL originates at the posterior, mid tibia (shin bone) and inserts into the distal portion of the second though fifth toes. FHL originates at the posterior middle fibula (smaller of the two lower leg bones) and inserts into the distal phalanx of the first toe. The tendons of these two muscles, along with the tibialis posterior tendon, pass behind the medial malleolus (inside ankle bone). If you have ever taken anatomy, you may have learned the acronym Tom, Dick and Harry to help you remember which order these tendons are in as they pass behind the malleolus.
Trigger points in your long toe flexors can cause pain in the soles of your feet when walking. They can also contribute to cramps in the smaller muscles of the bottom of your feet, which can lead to hammer toe and claw toe. FDL trigger points also cause pain in the metatarsal arch and under the toes. FHL dysfunction can cause pain and numbness under the big toe, and discomfort under the first metatarsal head (large knuckle involved in bunions).
Walking or running on uneven surfaces, such as rocky ground or a sandy beach, can cause trigger points to form in any of the above muscles. Also, if you have Morton’s foot (when second MTP joint extends further out than your other MTP joints, causing instability of the foot) this can cause you to walk on the inner edges of your foot which can overwork tibialis posterior and lead to trigger points there. Worn out shoes or any surface that causes rocking of the foot are sometimes blamed on trigger point formation of these deep calf muscles. Adjusting to wearing barefoot or minimalist style shoes, which are less stable by nature, especially when getting used to wearing them on uneven surfaces, can tire these muscles out.
Now that the weather is getting warmer and you may be doing more walking, running or hiking on uneven surfaces, educating yourself on how to treat trigger points in your deep hidden calf muscles can help! Check back for part 2 of this article for massage techniques and exercises to aid in conditioning for your spring and summer adventures.