Tibialis anterior is the large muscle that runs down the outside of the shin, its tendon can be felt at the front of the ankle.
Tibialis anterior is responsible to dorsiflex (lift the foot up) and supinate (turn it inwards) the foot including the extension of the toes.
Injury can occur through overuse particularly through running on hard surfaces or in activities where you have to change direction frequently. Pain may be felt when you bend your foot and toes up, and swelling may present over the tendon.
Rest and Physiotherapy to treat biomechanical anomalies / checking that footwear is appropriate are important aspects of injury management.