Predictors of functional task performance among patients scheduled for total knee arthroplasty

Osteoarthritis (OA) is a common health problem affecting more than 7 million Americans. Declines in strength, flexibility, and knee joint pain reduce functional ability and contribute to decisions for total knee arthroplasty (TKA). This study describes predictors of functional ability among knee patients scheduled for TKA and proposes a preoperative exercise program to improve functional ability. A total of 82 knee OA patients (average age = 62.7 +/- 7.48 years, 70% women) were recruited from a single orthopedic surgeon's office. Muscular fitness assessments included knee flexion, extension strength, and range of motion (ROM) of the surgical and nonsurgical knees. Functional ability was assessed by 6-minute walk, number of chair rises in 30 seconds, and time required to ascend and descend 2 flights of stairs. Perceived functional ability and pain were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index. Correlation matrices determined which measures of muscular fitness, pain, and perceptions were associated with measures of functional ability. Significant correlates were entered into regression equations that determined the significant predictors of the functional tasks. These regression equations identified flexion strength of the nonsurgical knee as predicting 24-45% of the variance of functional ability assessments that involved independent or consecutive knee movement. Other variables that, to a lesser degree, predicted performance of the functional ability assessments included knee joint ROM and body mass index. Because functional ability after TKA is strongly dependent on presurgical functional ability, future investigators may wish to examine the impact of improving presurgical functional ability of TKA patients through resistance training, particularly closed-kinetic chain exercises that transfer fewer forces through the knee joint.