Background

Numbness around a replaced knee is common but its effect on postoperative outcome is unclear. Joint awareness, an indicator of the integrity of replaced joints that correlates with patient satisfaction, might be affected by numbness. This study investigated the relation between numbness and patient-reported outcome measures (PROMs), including joint awareness and kneeling ability. We developed a Numbness score based on a 5-point Likert scale.

Methods

We retrospectively reviewed 404 patients (514 knees) underwent knee replacement at our institution between May 2007 and April 2019. PROMs, including the Numbness score, New Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS), and Forgotten Joint Score-12 (FJS-12), and other clinical and radiological data were collected from 311 patients (394 primary knee replacements) with complete data. Kneeling ability was evaluated using kneeling-specific items in KSS.

Results

Numbness score correlated with KSS-Symptoms (r=0.44) and KSS-Satisfaction (r=0.41), KOOS-Symptom (r=0.42), KOOS-Pain (r=0.44), KOOS-ADL (r=0.36), and KOOS-QOL (r=0.38), and FJS-12 (r=0.42). A multivariable regression analyses with the numbness score as the response variable suggested that the numbness score was better after midline incision than after anteromedial incision. A multivariable regression analyses with KSS-Kneeling as the response variable suggested that male sex, better postoperative knee flexion, and better numbness score were factors associated with better kneeling.

Conclusion

A worse Numbness score was correlated with inferior PROMs and affected inferior kneeling. Less numbness, male sex, and better knee flexion angle were positively associated with better kneeling.