Strategies utilized to transfer weight during knee flexion and extension with rotation for individuals with a total knee replacement

Effect of loading parameters on motor performance during a dynamic weight-shift task

Controlling weight shift (WS) is essential to performing motions safely and smoothly during daily and athletic activities. This study investigated the impact of loading parameters on the motor performance and difficulty level of a dynamic WS task performed while standing. Twelve healthy young adults (21.2 ± 0.9 years, 53.5 ± 7.4 kg) were asked to match the target and their weight loads using visual feedback displayed on a computer monitor. Motor performance was estimated by assessment of loading accuracy and pace of motor skill acquisition, measured as a proxy of difficulty level, was estimated by assessment of learning rate. As predicted, both loading accuracy values decreased with increasing target frequency. Notably, the interaction of loading size and frequency had a significant effect on loading accuracy, which was increasingly impaired as the weight load increased at frequencies greater than 0.5 Hz. Moreover, the pace of motor skill acquisition in a dynamic WS task while standing was affected by the weight-load speed independently of the weight-load size. These results indicate that loading accuracy is affected by both the weight-load size and frequency and that 0.5 Hz is a critical frequency at which the difficulty level increases during dynamic WS tasks while standing in healthy youths. These findings suggest that the adequacy of the initial settings used regarding loading size and frequency is an important consideration in rehabilitative and athletic training aimed at evaluating and improving WS while standing.

Analysis of a rotary task following total knee arthroplasty: Stair descent with a cross-over turn

Leg loading and knee angle differences have been reported in total knee replacement individuals during straight gait; however, little is known about the impact on the knee during turning. Rotary motions may be difficult following total knee replacement surgery; therefore, some individuals may develop strategies or utilize pre-surgical strategies in order to maintain function. The primary aim of this study was to identify differences in individuals with a total knee replacement as compared to their healthy counterparts during stair descent followed by a cross-over turn. Ground reaction force, knee angle and moments were recorded on 10 total knee replacement and 12 healthy individuals during stair descent followed by a turn and compared to walking straight. Variables were analyzed for the affected, unaffected and healthy knees during the gait cycle. On initial contact, the total knee replacement group had less ground reaction force on the affected leg compared to the unaffected leg (p = 0.021) and had delayed contact (p = 0.044) and a slower loading rate (p = 0.020) compared to healthy group. During mid-stance, the affected leg had less ground reaction force compared to the healthy leg (p = 0.049). The affected stance leg had less knee flexion during mid-stance in both the straight trial (p = 0.002) and turn (p = 0.010). Moment differed between straight and turn trials but not between groups. Stair descent with or without a turn was approached in a precautionary manner by individuals with a total knee replacement. Slow approach, reduced impact and weight-bearing with a more extended knee on the affected leg may suggest a protective strategy to avoid risk of fall.