Peroneal tendon subluxation although rare, is a commonly misdiagnosed cause of lateral ankle pain and instability. The orientation and depth of the lateral retromalleolar groove is a major contributor to peroneal stability, but is little understood. We attempt to quantify the groove using three directional mapping techniques.

Eight age and sex matched embalmed cadaveric feet were dissected to expose the peroneal tendons and the retromalleolar groove. A hand held digitiser was used to map the version and inclination of the groove in a 3D virtual environment. The length and depth of the groove and its orientation were calculated using the cartilage boundary and the centroid of the curved surface.

Four male and four female specimens (mean age 80 Yrs) were studied. The groove was noted to be concave in 62%, flat in 25 % and concave in 12.5 %. Flatter groove were more commonly noted in (2/4) females. There was a significant difference in length and width of the groove between male and female feet. The mean length of the groove in male specimens was 6.2cm (5.4–6.7cm), and in female specimens 5.5cm (4.4–5.9cm). The mean width in males was 5.3mm (5.0–6.1mm) and in females 4.5mm (3.7–5.3mm). There was no significant difference noted in the depth of the groove between male and female feet. The mean depth in males was 2.3mm (0.8–3.1) and in female 2.2mm (0–2.4mm).

Knowledge of peroneal groove geometry in treatment of peroneal tendon instability is important. There appears to be a consistent difference in the anatomy of the groove between the sexes. Although men have longer and wider grooves than woman, the depth is the same in both sexes.