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What is it?

Impingement describes the catching of bone or soft tissue against a surface which limits movement. This can be a bone spur, an ossicle, loose body or soft tissue/scar tissue. The presence of an os trigonum is a common cause of posterior ankle impingement, however its presence is not always symptomatic. Those patients that move the ankle to the extremes of its range of motion, particularly if repetitive, are most commonly affected. This includes ballet dancers, runners, football players and other elite athletes. An os trigonum is an extra piece of bone (ossicle) found at the back of the talus in the ankle, and as the toes point downwards this hits the tibia (shin bone) resulting in pain. If this is repeated it can cause the ossicle to become loose and irritate the tissue between it and the talus.



Patients typically complain of ankle pain along the back of the ankle, which can be present at rest as well as when weight-bearing and is associated with a reduced range of motion. The pain is exacerbated by pointing the toes downward, which causes an os trigonum or soft tissue to hit the tibia (shin bone).




Initial management includes analgesics and non-steroidal anti-inflammatory medication, activity modification and physiotherapy. Corticosteroid injections may also be considered.

With persistent pain and symptoms despite non-operative measures, arthroscopic (‘keyhole’) surgery can be considered to remove scar tissue, loose bodies and an os trigonum.


Your ankle will be in bandaging and a surgical boot will be provided to allow you to weight-bear protected. You will be provided with crutches for support. Elevation, as much as possible, is important in the first few weeks, and ankle movements within limits of bandaging is recommended. The bandaging will come down at 2 weeks and dressings changed, and at this stage I would allow the foot to go into a normal comfortable shoe. Physiotherapy can be started at this stage and non-impact activities permitted.


With regards to return to work, it is dependent on the amount of weightbearing required. If the work is sedentary and you can keep the foot elevated, then return after 2 weeks is satisfactory. Otherwise, return to work should be expected after 6 weeks.

Return to sports can permitted after 6 weeks, depending on the level of discomfort.

Return to driving will not be before 2 weeks and you must be able to perform an emergency stop. It is important to inform your insurance company of the type of procedure that has been undertaken to ensure the cover is valid.


Risks of Surgery

As with any surgery there are potential risks. This will be discussed in more detail during the consultation, however common complications are stiffness, swelling, nerve injury, infection, failure to resolve symptoms and clots.