Increasing knee flexion following total knee arthroplasty (TKA) has become an important outcome measure. Surgical technique is one factor that can influence knee motion. In this study, it was hypothesised that stripping of the posterior knee capsule could improve flexion and range of motion (ROM) following TKA. Patients who were undergoing TKA were prospectively randomised into two groups - one group (62 patients) were allocated stripping of the posterior knee capsule (PCS), the other group (66 patients) no stripping (no-PCS). The primary outcome was change in flexion and ROM compared to pre-operative measurements at three time points; after wound closure, 3months and 1year post-operatively. Secondary outcomes were absolute measurements of flexion, extension, ROM and complications. All operations were performed by a single surgeon using the same implant and technique. All patients received identical post-operative rehabilitation. There was a significant gain in flexion after wound closure in the PCS group (p=0.022), however there was no significant difference at 3months or 1year post-operatively. Absolute values of extension (p=0.008) and flexion (p=0.001) 3months post-operatively were significantly reduced for the PCS group. The absolute value of ROM was significantly higher for the no-PCS group at 3months (p=0.0002) and 1year (p=0.005). There were no significant difference in the rate of complications. Posterior capsular stripping causes a transient increase in flexion that does not persist post-operatively. We do not recommend routine stripping of the posterior knee capsule in patients undergoing TKA.