Background Non-contact knee injuries often occur when a stimulus alters decision-making during the flight phase of a landing task. We developed a novel protocol to study this paradigm.

Objective To evaluate biomechanical differences between failed and successful single-leg drop-jump landings requiring in-flight decision-making.

Design Cross-sectional study.

Setting Controlled laboratory setting.

Patients (or Participants) Thirty-two healthy male (n=16; 15.9±1.87 yrs.) and female (15.7±1.7 yrs.) competitive Ottawa area athletes with no history of musculoskeletal injury affecting functional performance.

Interventions (or Assessment of Risk Factors) Participants completed single-leg drop-jump landings from a platform aligned to their tibial plateau. The landing leg (left-right-both) was randomly assigned to the participant on a projector. Landings were categorized as ‘successful’ or ‘failed’ (defined as any loss of balance forcing a participant to adjust their base of support during landing).

Main Outcome Measurements Whole body kinematics (Vicon) and muscle excitation amplitudes (EMG) were normalized over the preparatory (flight) and reactive (landing) phases of the drop jump. Moving Average Convergence Divergence (MACD) analysed significant variables to identify when the differences began.

Results Participants landed with more trunk flexion (success: 21.8°±13.2°; failed: 30.3±17.2°) (p<0.05), more anterior pelvic tilt (success: 4.2°±5.4; failed: 7.7°±5.1°), and less lateral pelvic tilt towards the landing leg (success: 4.7±3.0°; failed: 2.7±3.7) during failed landings (p<0.05). Higher rectus femoris, biceps femoris and gluteus medius excitation amplitudes were also observed during the failed landings (p<0.05). MACD analysis identified that differences between failed and successful landings were initiated during the preparatory phase of the drop-jump.

Conclusions While biomechanical variables were significantly different during the landing phase, our novel MACD analysis identified that these differences initiated during the flight phase. Our findings also highlight that proximal joints play a critical role for landing successfully. Preventive training must therefore include how athletes prepare for a landing with a strong emphasis on upper body and proximal joint control.