Background This study aimed to assess whether use of continuous passive motion (CPM) could improve range of motion in patients after total knee arthroplasty (TKA), if it could affect the surgical wound aspect (SWA) and if it could influence on pain management after TKA. Methods We randomized 210 patients in two groups, 102 patients in the CPM group, who received a standard rehabilitation protocol together with CPM application; and 108 patients in the no-CPM group, without CPM. Variables as knee motion (flexion, extension, range of motion) and pain were measured before surgery, on the 1st, 2nd and 3rd postoperative day, and in the 2nd, 6th, 12th and 24th postoperative weeks following TKA. The SWA was determined by the “surgical wound aspect score” (SWAS) in the next 48 h after surgery. This scale analyzes swelling, erythema, hematoma, blood drainage and blisters. Results There was an improvement in the knee motion over the course of follow-up in both groups, without significant difference in flexion parameter. We found no significant differences in the total score of SWA, except for hematoma, with less severity in the CPM group. Furthermore, we found no differences in the others SWAS parameters and pain. Conclusions The application of CPM does not provide benefit to our patients undergoing TKA in terms of either improved flexion mobility or decreased pain. No relationship was found between the use of CPM and the global score of SWA following a TKA, except for a decrease in hematoma appearance.