Drop landing between subjects post anterior cruciate ligament reconstruction and uninjured controls: A biomechanical and neuromuscular analysis.

BACKGROUND

The capacity of functional testing to identify 'at-risk' landing strategies in return to sport evaluation has been questioned. The purpose was to evaluate if biomechanical and muscle activation patterns differ during a drop landing task in subjects post anterior cruciate ligament reconstruction against uninjured controls.

METHODS

22 subjects within two years of anterior cruciate ligament reconstruction who had returned to sport and 25 activity matched controls were recruited. Sagittal plane knee and hip biomechanics and muscle activation amplitudes were recorded during a single leg drop landing task. Discrete measures derived from waveforms were analysed using t-tests and Analysis of Variance models (α=0.05).

FINDINGS

Subjects post anterior cruciate ligament reconstruction displayed reduced knee (Effect Size = 1.2) and hip (Effect Size = 0.995) range of motion as well as reduced knee extension moments (Effect Size = 0.955) but exhibited no differences in quadriceps or hamstrings activation amplitudes versus uninjured controls.

INTERPRETATION

Adoption of reduced knee and hip excursion or "stiffened" landing pattern despite similarities in muscle activation suggests the presence of adaptive strategies reflecting incomplete recovery despite receiving clearance for returned to sport. This suggests presence of altered patterns of movement which may place at increased risk for reinjury.