Posterior ankle impingement syndrome is a condition where impingement occurs at the back of the ankle [2]. The most common cause of this is when soft tissues (such as muscles or ligaments) become ‘pinched’ between the talus (highest ankle bone) and tibia (shin bone) [13]. |  Impingement betwwen the calcaneus (heel bone) and tibia (shin bone) |
This type of impingement is shown on the picture at the very top of this page. Typically, the patient experiences pain with forced toe pointing movements, such as dancing, kicking a ball or running downhill [20]. An enlarged bony lump (posterior tubercle) on the back of the talus (highest ankle bone) may increase the likelihood of a person developing PAIS [12]. Additionally, in 7-14% of the population [9], this bony lump remains detached (in normal people it fuses during puberty). This detached bone is called the ‘os trigonum’ and on it’s own this is not particularly a problem, however in certain people it can increase the ‘pinching’ occurring at the back of the ankle and cause PAIS [6].
Posterior ankle impingement is quite a broad term and as such, there are many other structures in the back of the ankle which can become impinged and cause PAIS. Sometimes the calcaneus (heel bone) can compress structures against the tibia (shin bone) as seen in the second picture [13]. Note how the impingement is occurring between the heel bone and the shin bone, and the highest ankle bone is not involved [13].
Some of the soft tissue compressed includes:
- the 'ligament like' capsule which envelopes the ankle joint to provide stability (tibiotalar capsule) [13]
- some of the ligaments surrounding the ankle joint (posterior talofibular, intermalleolar and tibiofibular ligaments) [20].
- Additionally it is possible to impinge the tendon of the muscle which flexes the big toe (flexor hallicus longus). It is important to know however, that if there is an injury or problem with this tendon (such as tenosynovitis), it can appear very similar to PAIS [20].
