We assessed the long-term (20 years) outcome of closed reduction and immobilisation in 19 patients with an isolated fracture of the posterior malleolus of the ankle treated at a single hospital between 1985 and 1990. The assessments used were an Olerud functional questionnaire score, physical examination using a loaded dorsal and plantar range of movement measurement, radiological analysis of medial joint space widening, the Cedell score for anatomical alignment of all three malleoli, and the radiological presence of osteoarthritic change.

There were excellent or good results in 14 patients (74%) according to the Olerud score, in 18 patients (95%) according to loaded dorsal and plantar range of movement assessment, in 16 patients (84%) as judged by the Cedell score, and for osteoarthritis 18 patients (95%) had an excellent or good score. There were no poor outcomes. There was no correlation between the size of the fracture gap and the proportion of the tibiotalar contact area when compared with the clinical results (gap size: rho values -0.16 to 0.04, p ≥ 0.51; tibiotalar contact area: rho values -0.20 to -0.03, p ≥ 0.4). Conservative treatment of ‘isolated’ posterior malleolar fractures resulted in good clinical and radiological outcome in this series at long-term follow-up.