Abstract Objective To investigate the effects of the inclusion of motor imagery (MI) principles into early physical therapy on pain, disability, pressure pain thresholds (PPTs), and range of motion in the early postsurgical phase after total knee arthroplasty (TKA). Methods A randomized clinical trial including patients with knee osteoarthritis who have received TKA was conducted. Participants were randomized to receive five treatment sessions of either physical therapy with or without MI principles in an early postsurgical phase after a TKA (five days after surgery). Pain intensity (visual analog scale [VAS], 0–100), pain-related disability (short-form Western Ontario McMaster Universities Osteoarthritis Index [WOMAC], 0–32), pressure pain thresholds (PPTs), and knee range of motion were assessed before and after five daily treatment sessions by an assessor blinded to the subject’s condition. Results Twenty-four participants completed data collection and treatment. The adjusted analysis revealed significant group*time interactions for WOMAC (F = 17.29, P = 0.001, η2 = 0.48) and VAS (F = 14.56, P < 0.001, η2 = 0.45); patients receiving physiotherapy and MI principles experienced greater improvements in pain (Δ –28.0, 95% confidence interval [CI] = –43.0 to –13.0) and pain-related disability (Δ –6.0, 95% CI = –8.3 to –3.7) than those receiving physiotherapy alone. No significant group*time interactions for knee range of motion and PPTs were observed (all, P > 0.30). Conclusions The application of MI to early physiotherapy was effective for improving pain and disability, but not range of motion or pressure pain sensitivity, in the early postsurgical phase after TKA in people with knee osteoarthritis.