Introduction
Pain localized to the lateral ankle region is often attributed to subtalar joint degeneration or sinus tarsi syndrome.
However,
extraarticular soft-tissue and osseous impingement is an unrecognized entity that can cause lateral ankle pain.
The impingement occurs lateral to the ankle joint as a result of flatfoot deformity with resulting talocalcaneal subluxation and valgus hindfoot malalignment.
Lateral hindfoot impingement is often seen in patients with severe hindfoot deformity secondary to congenital or acquired flatfoot deformity.
Other causes of lateral hindfoot impingement include tarsal coalitions,
calcaneal fracture malunion,
neuropathic arthropathy and inflammatory arthritis (table 1).
Patophysiology
Lateral hindfoot impingement is an extrarticular soft-tissue and osseous impingement that occurs lateral to the ankle joint that as been shown to result from a lateral shift in the weight-bearing forces from the talar dome to the lateral talus and fibula, combined with subluxation of the talocalcaneal joint.
It can be divided into talocalcaneal impingement,
subfibular impingement and combined talocalcaneal-subfibular impingements.
Talocalcaneal impingement occurs between the lateral talus and calcaneus and subfibular impingement occurs between the calcaneus and the fibula.
The later is usually preceded by talocalcaneal impingement (figure 1).
Lateral hindfoot impingement is characteristically not related to an acute injury but to chronic hindfoot valgus malalignment which is often due to posterior tibial tendon insufficiency ,
as this tendon is crucial in maintaining the longitudinal arch of the foot.
This leads to contact between the inferior aspect of the talus with the superior aspect of the calcaneus in the sinus tarsi (at the point of the angle of Gissane).
Also,
patients with flatfoot and impingement show higher talonavicular abduction angles on weight bearing radiographs.
Talonavicular abduction results in an increase in the anteroposterior talocalcaneal angle,
causing the calcaneus to abduct and evert.
This likely allows the calcaneus to move closer to the fibula and also facilitates lateral subluxation of the posterior facet of the subtalar joint and results in hindfoot valgus.
Since the sinus tarsi opens in inversion and closes in eversion,
hindfoot valgus causes a narrowing of the sinus tarsi.
Peroneal tendon subluxation is also observed in patient with lateral impingement,
possibly resulting from the proximity of the calcaneus to the fibula with advanced posterior tibial tendon dyfunction that leads to crowding and subsequent dislocation of the peroneal tendons of the retromalleolar groove.
Clinical Presentation
Lateral hindfoot impingement most commonly occurs in middle-aged and older individuals with a chronic hindfoot valgus deformity.
Clinical presentation varies on the basis of the cause of flatfoot and hindfoot valgus.
Symptoms often include hindfoot pain on weight-bearing,
swelling and tenderness in the region anterior and inferior to the lateral malleolus,
and limited subtalar range of motion.
These clinical symptoms are not specific and may also be encountered in patients with subtalar degenerative arthritis,
sinus tarsi syndrome,
and other disorders affecting the hindfoot region.
Posterior tibial tendinopathy is a common cause of hindfoot valgus deformity.
These patients experience pain that is initially located along the medial aspect of the foot,
often associated with swelling due to tenosynovitis.
With progressive collapse of the longitudinal arch and development of a hindfoot valgus deformity,
lateral foot pain develops and is frequently related to lateral hindfoot impingement (table 2).
Progressive deformity,
secondary osteoarthrosis of the subtalar,
talonavicular,
and calcaneocuboid articulations contribute to pain symptoms in cases with extraarticular lateral ankle impingement.