Background: Low-intensity pulsed ultrasound is a physiotherapy treatment modality that has shown positive effect on the recovery of knee range of motion (ROM) after total knee arthroplasty (TKA) other than helps to relieve inflammation and improve joint function. However, whether the recovery of knee ROM of post-TKA following the low-intensity pulsed ultrasound is influenced by the recovery of postoperative pain or not, is still unknown. Purpose: This study aimed to examine the effect of low-intensity pulsed ultrasound on the recovery of knee flexion range of post-TKA after controlling for postoperative pain following the intervention. Methodology: This was an assessor-blinded quasi-experimental study. Thirty-two post-TKA patients at the Hospital Canselor T uanku Muhriz Universiti Kebangsaan Malaysia were alternately allocated to an experimental group (n = 16, received low-intensity pulsed ultrasound and conventional physiotherapy) and a control group (n = 16, received conventional physiotherapy alone). Intervention was administered for 3 weeks (postoperative week 1 had 4 sessions/week, postoperative week 2β3 had 1 session/week). Pain and active knee flexion range were assessed using visual analogue scale and goniometer respectively: at baseline (postoperative day-2) and 1-week follow-up after the intervention. Data was analyzed using independent t-test and one-way ANCOVA. Results: The postoperative pain following the intervention was significantly different between the groups (meanSD = 1.641.40 vs 3.401.50, p < 0.01). After controlling for the postoperative pain following the intervention, there was a statistically significant effect of the intervention on the active knee flexion range (F(1,29) = 13.50, p = 0.001, p2 = 0.32), where the participants in the experimental group showed significantly greater knee flexion range than the control group. Conclusion: Low-intensity pulsed ultrasound as an adjunct to conventional physiotherapy provides better effect in the recovery of active knee flexion range of patients with TKA