Tarsal tunnel syndrome. Causes and results of operative treatment. From 1975 to 1988, operative treatment was performed on 50 feet in 45 patients with tarsal tunnel syndrome. The causes of this syndrome were correlated with operative findings and included ganglia in 18, and a bony prominence from talocalcaneal coalition in 15. Five feet had sustained an injury, tumours were found in three and there was no obvious cause in nine. In most cases in need of operative treatment, there was a space-occupying lesion. Classifying the results according to causes, those with coalition or a tumour fared better, and idiopathic and traumatic cases had a worse outcome. In cases with a definite lesion, an excellent result can be expected from surgical treatment carried out soon after onset of the condition. 