Rossi MD, Brown LE, Whitehurst M; Florida Atlantic University, Davie, Florida. mark.rossi@sunysb.edu.

PURPOSE: The purpose of this repeated measures study was to document the early history of knee extensor torque production before, 30, and 60 days after unilateral TKA. SUBJECTS: A total of 38 individuals (19 males, 19 females: 72.23 ( ± 5.34) years, height 168.00 ( ± 8.57) centimeters, and weight 79.42 ( ± 14.57) kilograms) with severe knee joint osteoarthritis participated in this study. All subjects received physical therapy outpatient services 3x/week for 8 weeks, after discharge from the acute care setting. Range of motion for all subjects ranged from 5 to 132 degrees of flexion. The lowest available knee flexion range was 85 degrees. METHODS AND MATERIALS: A Cybex isokinetic system was used in this study to quantify knee extensor torque production. Each subject was instructed to perform three repetitions ("as hard and as fast as they could") at speeds of 60 and 180 deg./sec., completing their full available range of motion. Testing was completed before surgery (pre), 30 days, and 60 days after surgery. The uninvolved side was tested before surgery. The highest peak knee extension torque (Nm) that occurred within the three repetitions was recorded. ANALYSIS: A paired t-test was used to assess for differences in knee extensor torque production between limbs, before surgery, at 60 and 180 deg./sec. Two one-way repeated measures analysis of variance (ANOVA) with follow-up contrasts were used to assess for differences in knee extensor torque production of the involved limb at 60 and 180 deg./sec., between the three periods. RESULTS: Before surgery, the involved limb produced 65% and 74% of the torque of the uninvolved limb at 60 (p = 0.0001 < 0.0125) and 180 deg./sec. (p = 0.0001 < 0.0125), respectively. The knee extensors 30 days post surgery, on the involved side generated 67% and 78% of the torque compared to before surgery at 60 (p = 0.0001 < 0.002) and 180 deg./sec. (p = 0.001 < 0.002), respectively. Sixty days post-surgery the knee extensors on the involved side produced 35% and 26% more torque compared to 30 days at 60 (p = 0.0001 < 0.002) and 180 deg./sec. (p = 0.001 < 0.002), respectively. There was no difference in torque production between 60 days and pre-values. CONCLUSIONS: The first month after surgery may be an important point in knee extensor recovery. Knee extensor force production remains impaired through 60-days. Intensity and frequency of rehabilitation after TKA may need to be re-assessed in an effort to minimize knee extensor impairment after surgery. The duration of Physical Therapy services may need to be extended up to and beyond the 60-day period. FUNDING SOURCE: None.

Copyright 2004 by the American Physical Therapy Association

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