Ankle Impingement

Ankle impingement is pain and restricted movement caused by bone or soft tissue being trapped at the front or back of the ankle at the end of range.

It is classified by site:

• •Anterior: pain on dorsiflexion, from tibial and talar osteophytes or soft tissue (footballer's ankle)
• •Anterolateral: soft tissue scarring in the lateral gutter after a lateral ankle sprain
• •Posterior: pain on forced plantarflexion, usually from an os trigonum or prominent posterior talar process (dancer's ankle)

Impingement may be bony, soft tissue or both. Anterior osteophytes may be an early feature of ankle osteoarthritis (OA) or exist on their own.

Anterior: in dorsiflexion the anterior tibial margin and talar neck come together. Osteophytes from repetitive dorsiflexion loading (football, rugby, uphill running, squatting) or previous injury block dorsiflexion and pinch the capsule and synovium. Soft tissue causes include a thickened capsule, synovitis and meniscoid lesions.

Anterolateral: after a lateral ankle sprain, scar tissue, hypertrophied synovium and thickened capsule fill the anterolateral gutter. A thickened distal fascicle of the anterior inferior tibiofibular ligament (AITFL), Bassett's ligament, can impinge on the talus. Chronic instability and impingement often coexist.

Posterior: in forced plantarflexion, as in ballet dancers en pointe, footballers and fast bowlers, the posterior talar process is compressed between the tibia and the calcaneus. Causes include:

• •Os trigonum: an unfused lateral tubercle of the posterior talar process, a normal variant in about 7 to 14% of people
• •Stieda process: an elongated lateral tubercle
• •Flexor hallucis longus (FHL) tenosynovitis: the FHL runs between the medial and lateral tubercles and is often involved, particularly in dancers