Determinants of function after total knee arthroplasty

Decreasing hospital stays for patients with total knee arthroplasties (TKAs) have a direct effect on rehabilitation. The identification of modifiable determinants of postsurgical functional status would help physical therapists plan for discharge from hospitals. The purpose of this study was to identify preoperative determinants of functional status after a TKA.

Using a community-based, prospective cohort study, data were collected from 276 patients who received a primary TKA in a Canadian health care region. Data were collected in the month before surgery and 6 months after surgery.

Function was measured using the function subscale of a disease-specific measure--the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index--and a generic health status measure--the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). Independent variables examined included demographic variables (eg, age, sex), medical variables (eg, diagnosis, number of comorbid conditions, ambulatory status), surgical variables (eg, type of implant, number of complications), and knee range of motion.

At 6 months after surgery, the average WOMAC physical function score was 70.5 (SD=18.2) and the average SF-36 physical function score was 44.8 (SD=25.3). Using multiple regression analyses, baseline function, walking device, walking distance, and comorbid conditions predicted 6-month function (WOMAC: R2=.20; SF-36 physical function: R2=.27).

Patients who have lower preoperative function may require more intensive physical therapy intervention because they are less likely to achieve functional outcomes similar to those of patients who have less preoperative dysfunction.