50 patients undergoing primary unilateral knee arthroplasty with an adductor canal block were randomized to either proximal or distal adductor canal catheter insertion. The purpose was to compare time to anaesthesia onset between the two insertion sites, and the effect each had on motor block. The results demonstrated no significant differences between groups in time to onset of sensory anaesthesia. A number of patients in both groups demonstrated at partial or complete motor block, with quadriceps weakness recorded in 19/25 of the proximal group and 16/24 in the distal group.