Flexor Hallucis Longus Tendonitis

Anatomy & Function

The flexor hallucis longus (FHL) tendon is one of three structures that lie in the tarsal tunnel. Running behind the medial malleolus (inside ankle bone), the FHL is the most posterolateral (to the rear and side). The FHL runs forward into the foot to insert onto the distal phalanx (the end bone) of the great toe. The FHL acts as a flexor of the great toe, elevates the arch, and assists with plantar flexion of the ankle (pointing the toes away from the body).

Location of the Flexor Hallucis Longus

Diagnosis And Treatment

Patients with FHL Tendonitis usually present with pain in the posteromedial aspect of the ankle (behind the inside ankle bone). The pain improves with rest and increases in sports requiring push-off and extended running. Usually no palpable tenderness is present due to the deep location of the tendon. Pain and weakness are noted with resistance to plantar flexion of the first MTP joint. Pain also may be present in the tarsal tunnel (the area just back of the inside ankle bone).

FHL tendonitis typically is associated with repeated push-off maneuvers, such as those executed by ballet dancers or sprinters. Sometimes blunt trauma and repetitive impact may also play a role. FHL tendonitis may occur at three sites. These are: the entrance of the fibro-osseous tunnel between medial and lateral talar tubercles (the prominent ankle bones on then inside and the outside part of the ankle); the flexor sheath behind medial malleolus (inside ankle bone); between the sesamoids (small bones) of the great toe.

Among the conditions that can look like this are: Achilles tendinitis, Posterior Tibial Tendonitis, and tarsal tunnel syndrome.

Clinical findings include: swelling, pain, and tenderness posterior to the medial malleolus; triggering and pain along tendon sheath that may occur with toe flexion (bending the toe down); and reduced ability to point the great toe up. Plain x-rays of the foot are helpful with the differential diagnosis, and US imaging or MRI can help rule out a tear.

Treatment consists of immobilization, activity restrictions, and NSAIDs. Orthotics may be used as a conservative measure - steroid injection is possible but caution must be exhibited because of the nerves and blood vessels in the area. in severe cases surgery is sometimes required.