Does Skin-Surface Temperature Reflect Recovery After Total Knee Arthroplasty? A Prospective Pilot Study with Infrared...

Background/Objectives: Persistent skin-temperature changes have been described following total knee arthroplasty (TKA), but their clinical significance remains unclear. The aim of this study was to compare regional knee temperature before surgery and six months after TKA using infrared thermography. Secondary objectives were to evaluate regional thermal patterns and investigate their association with patient-reported clinical outcomes. Methods: Twenty patients undergoing primary TKA for knee osteoarthritis underwent standardized thermographic assessment preoperatively and after six months. Thermograms were acquired at rest (T0), after a two-minute standardized flexion-extension exercise (T1), and after five minutes of recovery (T2). Mean temperatures were calculated for the whole knee and four regions of interest (ROIs). Pain and function were assessed using the Numerical Rating Scale (NRS) and Oxford Knee Score (OKS). Associations between thermographic findings and clinical outcomes were explored. Results: Whole-knee temperature was significantly higher at six months than before TKA at all three measurement phases (mean increase, 1.1-1.3 °C; all p ≤ 0.002). Exercise induced a transient decrease in temperature both before and after surgery, with no significant change in response magnitude between assessments. NRS pain decreased significantly, whereas OKS improvement was small and did not reach statistical significance (2.15 ± 21.83; p = 0.665). NRS improvement correlated inversely with T0 change, most strongly in the lateral ROI (r = -0.903), with greater postoperative temperature increases being associated with less pain improvement. Higher postoperative T2 temperatures were associated with lower OKS scores at follow-up and less OKS improvement across the whole knee and all four ROIs (r = -0.577 to -0.755). Conclusions: Skin temperature remained significantly higher six months after primary TKA compared with preoperative values, and higher thermographic values were associated with less favorable clinical outcomes. These preliminary findings, based on exploratory analyses not adjusted for multiple comparisons, support further investigations into infrared thermography as a complementary source of information on postoperative recovery after TKA.