Flexor digitorium longus
Flexor digitorum longus originates in the deep posterior compartment of the leg medial to flexor hallucis longus and superficial to tibialis posterior. Due to the deep location of the muscle belly, it is once again, extremely difficult to isolate with palpation. The tendon however, may be palpated as it passes behind the medial malleolus with tibialis posterior. To activate the muscle and cause the tendon to become prominent, ask your subject to plantarflex their lesser toes against resistance. Repeated flexion contractions of the digits will aid in distinguishing the flexor digitorum longus tendon from tibialis posterior.