Extensor digitorum longus tendinopathy and synovitis

Findings

Pain in the anterior compartment of the lower leg and/or under the anterior retinaculum at the ankle, which is tender to palpation and worse with resisted toe extensors. There may be audible and palpable crepitus. The skin over the tendons may be red and sore. Examination of the inside of the shoe near the toes often reveals a hole or pit that is being worn away by the dorsiflexed hallucis. Weak painless extensors of the toes are likely to be caused by L5 nerve palsy.

Cause

Overuse of extensors of the toes, or rubbing of the extensor tendons by the shoes. These muscles are used either to protect an unstable foot or ankle, when they lock up together with the calf, posterior tibialis and peroneals, producing a solid foot at impact, or when they try and do the work of the posterior tibialis and hold up the long arch of the foot. This occurs in inexperienced runners who run and impact into the midstance phase, which collapses the longitudinal arch. The dorsiflexors can be overused by shuffle runners, who dorsiflex the foot and toes in the swing phase.

Sports

a) Avoid inclined or ordinary sit-ups with the feet under a bar, or held by a colleague, for leverage.

b) Inexperienced cross-country skiers may concentrate on sliding the ski forwards by dorsiflexing the foot and toes.

c) "Shuffle runners", who do not thrust from the forefoot to achieve lift-off, may have to dorsiflex their toes and feet faster to clear the ground at take-off.

d) Step aerobics and hill running may lead to increased dorsiflexion of the foot and toe.

Some of these runners will wear a hole in the top of their running shoe, from the big toe nail pulling up into the shoe during the swing phase of running. Lacing up the shoes too tightly does not allow room for the tendons to bridge the joints without rubbing into the shoe. Padding either side of the affected tendon will distribute the pressure points away from the tendon itself. This can be sufficient to relieve the problem as it is very difficult to change this particular running style. An orthotic which helps to reduce pronation also reduces the need for the supporting muscles to lock up, which it the athletes' way of preventing overpronation, especially in an externally rotated foot.

"Concise guide to sports injuries, 2^nd edition",Churchill Livingstone, Malcolm T.F. Read,  foreword by Bryan English