The effect of numbness on outcome from total knee replacement

INTRODUCTION Some patients report continuing pain and functional limitations after total knee replacement (TKR). While numbness around the TKR scar is common, the impact of numbness is less clear. One particular activity that could be influenced by numbness is kneeling. The aim of this study was to explore the impact of numbness around TKR scars on health related quality of life and kneeling ability. METHODS Fifty-six patients were recruited one year after primary TKR. Sensation around the knee was assessed through patient self-reporting, monofilament testing and vibration, and patients' distress was measured on a visual analogue scale. Patient reported outcome measures (PROMs) including the Western Ontario and McMaster Universities (WOMAC r) index, the Knee injury and Osteoarthritis Outcome Score (KOOS), the painDETECT r (Pfizer, Berlin, Germany) questionnaire and the EQ-5D T (EuroQol, Rotterdam, Netherlands) questionnaire were used. Participants were also asked about kneeling ability. RESULTS While 68% of patients reported numbness around their TKR scar, there was no statistically significant correlation between numbness and distress at numbness (self-report: 0.23, p= 0.08; monofilament: 0.15, p= 0.27). Furthermore, numbness did not correlate significantly with joint specific PROMs (WOMAC r : 0.21, p= 0.13; KOOS: 0.18, p= 0.19). However, difficulty with kneeling did correlate with both self-reported numbness (0.36, p= 0.020) and worse PROM scores (WOMAC r pain subscale: 0.62, p< 0.001; KOOS: 0.64, p< 0.001). CONCLUSIONS Numbness after knee replacement is common but is not associated with worse patient reported outcomes.