Landing style differences between anterior cruciate ligament deficient and healthy subjects
- Dr. Nicki Phillips
- Kate Button
- Dr. Robert van Deursen
Deceleration during landing challenges knee stability, which is particularly difficult for patients with ACL deficiency (ACLD), potentially requiring adaptation of landing style. This study aimed to identify the mechanism of such an adaptation in landing technique.
Thirty ACLD patients (non-reconstructed) and 30 control subjects performed a run and stop task. They landed on a force plate whilst kinematic, kinetic and electromyographic data were recorded. Sagittal net joint moment and work were calculated. Polar coordinates of the centre of the pelvis relative to the ankle joint were used to determine control of landing angle and limb shortening during deceleration (telescopic inverted pendulum).
All participants were able to carry out this deceleration task without events of giving way. Despite the significantly slower approach velocity (ACLD: 2.15 ± 0.36 m/s vs. Control: 2.38 ± 0.39 m/s; p<0.01), ACLD patients took significantly longer to decelerate (205.3 ± 37.5 ms vs. 157.5 ± 29.5 ms; p<0.05) and took longer to achieve stable stance (p<0.01). Landing style differed significantly, with ACLD patients landing more upright (p<0.01). They used change in landing angle more (p<0.01) and limb shortening less (p<0.01) than control subjects. Net knee moment was significantly reduced in the ACLD patients (230.8 ± 75.1 N.m vs. 278.6 ± 80.3 N.m; p<0.05). Absorption work during deceleration was significantly increased at the ankle joint (23.6 ± 4.1 J vs. 16.2 ± 12.1 J; p<0.05) and significantly decreased at the knee joint in the ACLD group (54.7 ± 35.3 J vs. 107.5 ± 70.9 J; p<0.05). No between-group differences in EMG onset were observed.
Adaptations in landing style for the ACLD group meant their landing technique relied more on ankle and less on knee control compared to healthy subjects. This knee avoidance technique was less effective to achieve deceleration but presumably protects the knee from instability.