Comparison of early postoperative activity-related pain burden after conventional, navigation-assisted, and robotic-assisted total knee arthroplasty: a retrospective cohort study based on 24-72 h pain area under the curve.

Early pain after total knee arthroplasty (TKA) can limit walking and knee training. Movement-related pain may be particularly relevant because it occurs during passive knee training, walking, and weight-bearing activity. Navigation and robotic systems can help the surgeon plan bone cuts, place implants, and balance soft tissue. However, surgeons still do not know whether these tools lower the overall pain burden during early recovery. This point is especially important for pain that appears during movement. This study compared early pain after conventional, navigation-assisted, and robotic-assisted TKA. We used the area under the curve (AUC) to describe cumulative pain from 24 to 72 h after surgery. We retrospectively reviewed 169 patients undergoing primary unilateral TKA from April 2025 to April 2026. Patients were grouped as conventional (n = 78), navigation-assisted (n = 39), or robotic-assisted TKA (n = 52). The primary outcome was the 24-72 h area under the curve (AUC) of visual analogue scale (VAS) pain during passive knee flexion-extension. Secondary outcomes included resting pain AUC, time-point VAS scores, walking pain at discharge, rescue analgesic frequency, morphine-equivalent consumption, early range of motion, swelling, quality of recovery, 3-month Knee Society Score, hospital stay, and complications. Multivariable regression adjusted for measured confounders. The study included 169 patients. Seventy-eight patients received conventional TKA, 39 patients received navigation-assisted TKA, and 52 patients received robotic-assisted TKA. The three groups had similar measured baseline features. Resting-pain AUC from 24 to 72 h did not differ among the groups. Passive-motion pain AUC differed significantly among the groups. The robotic-assisted group had a lower cumulative movement-related pain burden than the conventional group. The navigation-assisted group showed a lower AUC estimate, but this difference was not significant after adjustment. The difference between the robotic-assisted and navigation-assisted groups was not significant. Passive-motion VAS at 36 and 48 h was lower after robotic-assisted TKA than after conventional TKA. Walking pain at discharge was also lower in the robotic-assisted group. The groups did not differ in rescue analgesic frequency, morphine-equivalent rescue analgesic consumption, knee swelling, ROM recovery, QoR-15, length of stay, complications, or 3-month KSS. Robotic-assisted TKA was associated with lower early movement-related pain burden than conventional TKA, but the absolute time-weighted VAS difference was modest. These findings should be interpreted as associations rather than causal evidence of superiority. Movement-related pain AUC may be useful for evaluating early rehabilitation pain after TKA.