The role of continuous passive motion after total knee arthroplasty

The usefulness of continuous passive motion after total knee arthroplasty remains controversial. The reported benefits include decreased rates of knee manipulation, deep vein thrombosis, and postoperative use of analgesics, and a greater range of motion. Other studies have reported increased wound complications, bleeding, and pain. Lack of consensus on the use of continuous passive motion exists because reported studies include many confounding variables. Several studies have shown that continuous passive motion in the hospital decreased the rate of knee manipulation from as high as 21% to as low as 0%. Although many studies show that range of motion may improve more rapidly with continuous passive motion, the ultimate range of motion at followup is unchanged. At the author's institution, continuous passive motion is used three times per day (1 hour sessions), beginning on the first postoperative day, within a 4 to 5 day inpatient hospital pathway. Of 132 knees that had a primary posterior-stabilized total knee arthroplasty, seven knees (5%) had a manipulation for failure to obtain greater than 70 degrees flexion. No patients had major wound complications that required reoperation. There is no specific charge to the patient for the continuous passive motion because it is included in the hospital per diem charge. The literature and the author's data support the use of continuous passive motion to decrease the rate of manipulation (and its costs) for poor range of motion after total knee arthroplasty. If patients follow fixed inpatient hospital pathways, the length (and possibly cost) of hospital stay is not changed by use of continuous passive motion. The data on the effect of continuous passive motion on overall analgesic use and prevalence of deep vein thrombosis are not clear.