Increased knee joint circumference after total knee arthroplasty, should we care?

BACKGROUND: Knee swelling is common after total knee arthroplasty (TKA). However, there is limited literature on its clinical implications. OBJECTIVE: The study aimed to determine whether a correlation exists between increased postoperative knee circumference, pain, functional score and range of motion. METHOD: Between November 2019 and June 2020, 114 patients were retrospectively enrolled in this study. Primary endpoints included the correlation between knee circumference change (KCC, and 1) postoperative pain 2) Oxford Knee Score, and 3) postoperative range of motion. These data were collected on day 2 and at 6 months postoperatively. RESULTS: The mean knee circumference (KC) increase on postoperative day 2 was 9.27%. No statistically significant correlation was found between KCC and pain (p = 0.853), KCC and patient-controlled analgesia (PCA) consumption (p = 0.265), KCC and knee flexion (p = 0.729) and extension (p = 0.157). At 6 months postoperatively, no statistically significant correlation was found between KCC and pain (p = 0.909), and Oxford Knee score (p = 0.137). However a statistically significant correlationwas observed between increasedKCof more than 10% and extension deficit at 6 month postoperatively (p = 0.012), as well as between KCC on day 2- and at 6 months postoperatively. CONCLUSION: After TKA the average increase in KC is around 10%. Increased postoperative knee effusion is neither an indicator for increased pain nor for unfavorable functional scores. At 6 months postoperatively, a correlation exists between increased KC and extension deficit for knees with more than 10% KCC. This study addresses common patient inquiries to physiotherapists regarding knee swelling following TKA.