Knee Biomechanics of Replaced and Non-replaced Limbs during Level Walking Following Total Knee Arthroplasty

Abstract

Previously we showed that total knee arthroplasty (TKA) patients still showed deficiencies in replaced limbs in a stair ascent test compared to healthy subjects. These differences were mainly reflected in the reduced peak frontal plane ankle moments but elevated peak frontal plane hip moments at a similar preferred ascent speed. However, peak knee sagittal- and frontal-plane moments were similar. PURPOSE: To compare knee biomechanics of replaced and non-replaced limbs of TKA participants and control limbs of age and body mass index (BMI) matched healthy controls in level walking. METHODS: A total of 13 TKA (65.6 yrs, 28.3 BMI & 24.5 months from TKA surgery) and 15 healthy (62.3 yrs & 27.1 BMI) participants performed functional tests and five level walking trials at a preferred speed. A one-way ANOVA was used to detect difference between replaced, non-replaced limbs and healthy controls (p<0.05). RESULTS: TKA participants had a slower level walking speed (1.18m/s) than healthy controls (1.40m/s, p<0.001); they also had slower stair ascent and descent times on an 11-step staircase but similar timed-up-and-go times compared to healthy controls. The push-off peak vertical ground reaction force (GRF) was reduced in replaced limbs [1.04±0.05 body weight (BW)] compared to control limbs (1.10±0.05 BW). The peak knee extension moment during loading response was decreased in both replaced (0.54±0.23 Nm/kg) and non-replaced (0.54±0.35 Nm/kg) limbs compared to control limbs (0.83±0.27 Nm/kg). The loading response peak internal abduction moment was also reduced in replaced limbs (-0.35±0.13 Nm/kg) compared to control limbs (-0.54±0.18 Nm/kg). CONCLUSIONS: After rehabilitation and recovery, the TKA patients still demonstrated slower walking speeds. The reduced speeds were accompanied by decreased peak GRF, peak sagittal-, and frontal-plane knee moments in replaced limbs, and reduced peak sagittal-plane moment in non-replaced limbs of TKA patients. The results are in contrast to the stair ascent results showing similar peak knee moments between the replaced, non-replaced and control limbs. The differences may be related to different roles or strategies played by knee, hip and ankle muscles in level walking and stair ascent, suggesting that both tests are necessary in order to detect deficits of TKA patients.