A case presented in the clinic this week of a very athletic client who had previously suffered a muscle strain/tear in their calf muscle. This had been treated well initially, but on trying to return to running, they suffered ongoing pains in the base of their Achilles tendon and around the back of their ankle. Despite having ongoing bouts of rest, massage and return to running, their symptoms returned as soon as they tried to increase their running distances or run over uneven terrain.
On assessment, this client had no palpable pain around their ankle, but on testing the forced passive ankle plantarflexion test, where the ankle is rapidly moved into plantarflexion, a highly positive result was noted. A referral for an x-ray confirmed that this client was suffering from a Stieda process involving the talus.
The two most common causes for posterior ankle impingement are a Steida process, which is an enlargement of the posterolateral talar process, or an os trigonum, which is a secondary ossification site of the talus which does not fuse through teenage years and the remaining bone remains separated from the talus.
Figure 1: Os trigonum (left) and Stieda process (right)
These two conditions are often asymptomatic, but can be irritated from either repetitive loading in plantarflexion (e.g. standing on tip toes), causing the bony prominence to be pinched between the calcaneus and tibia, or trauma to the area resulting in irritation or fracture of the bony prominences.
Treatment of this condition is usually conservative including activity modification, physiotherapy intervention including bracing or soft tissue stretches to increase plantar flexion range of motion, anti-inflammatory medications, and immobilisation for severe cases. Corticosteroid and local anaesthetic injections have also shown benefit in reducing pain symptoms and increasing functional capacity.
Where conservative treatment does not allow the person to return to sport, surgical techniques including a posterior ankle arthroscopy to remove the bony fragments or debride the Stieda process can be utilised to remove the impingement.
