posterior ankle impingement syndrome
Posterior ankle impingement (PAI) syndrome is one of the impingement syndromes involving the ankle. It is classically described in ballet dancers.
It is usually a unilateral phenomenon. Bilateral posterior ankle impingement syndrome has been described but is rare .
Patients usually present with a sharp pain at the back of the ankle upon plantar flexion. The pain might persist for some time after such a movement.
Thought to occur from repetitive ankle plantar flexion leading to soft tissue compression, synovitis, capsulitis and eventually scarring .
Predisposing anatomical factors
- Stieda process
- os trigonum
- fracture involving lateral tubercle of the posterior process of the talus
- prominent superior surface of calcaneal tuberosity
- prominent downslope of the posterior tibial articular surface
- any abnormal calcification/ossification posterior to the ankle
- may demonstrate posterolateral capsular thickening and synovitis involving an intact posterior talofibular ligament (PTFL)
- there may be tenosynovitis involving the flexor hallucis longus (FHL)
- may show one or more of the predisposing anatomical factors
- accompanying bone contusion may be present, involving the lateral tubercle of the posterior talar process
- localized fluid and/or edema in the posterior joint recesses
MRI signal characteristics
- T1: low signal in areas of bone bruising
- T2/STIR: high signal posterior to ankle in areas of bone bruising
- PD/PD fat saturated: high signal posterior to the ankle