Impact of continuous passive motion on rehabilitation following total knee arthroplasty

There is an ongoing controversy in respect of the usage of continuous passive motion (CPM) following total knee arthroplasty (TKA). We analysed the impact of CPM on the early rehabilitation after TKA and the clinical outcome over the time.

Forty patients were prospectively randomized to postoperative protocols following TKA. Half of them (n = 20) received the standard manual therapy alone and the others (n = 20) were treated additionally with CPM. Identical implants were used in all patients. Passive range of movement (PROM) was noted. Patient satisfaction and knee function was evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) as well as the Knee Society Score (KSS) at time of discharge and 2 years postoperatively.

The patients in the solitary manual therapy group (MT) showed preoperatively a 7.2° greater PROM (p = .03) with 5.4° higher flexion (p = .05). Analogously, the KSS presented with 42.7 points a higher score result compared to the CPM group with 35.9 points (p = .03). Although the preoperative ability with 105.2° for flexion and 97.2° for the PROM were in favour of the group without CPM (99.8° resp. 90.0°), at time of discharge the patients with CPM reached with 111.0° a significant higher flexion and with 109.0° a higher PROM (MT group: 107.0° resp. 103.5°) (p = .04/.02). At 2 years follow-up both scores (WOMAC/KSS) and function (extension, flexion and PROM) were balanced (p > .05). Patella resurfacing showed no impact on the clinical results at discharge or at time of last follow-up (p > .05).

Although the addition of CPM did significantly improve knee flexion in the early postoperative stage, the difference might not represent a clinical relevance. Further, there were no notable effects on long-term clinical and functional results following TKA, so the routine application of CPM in the above stated setting might be ceased.