Commonly, landing biomechanics during a bilateral drop vertical jump (DVJ) are assessed in patients with, or at risk for, anterior cruciate ligament (ACL) injury (Hewett et al., 2005, Myer et al., 2010, Paterno et al., 2010, Paterno et al., 2007). Landing biomechanics assessed during the DVJ have been reported to predict risk for primary (Hewett et al., 2005) and secondary (Paterno et al., 2010) ACL injury in young athletes. Other research (Krosshaug et al., 2016, Petushek et al., 2021) suggests this is not the case in elite female athletes. Importantly, significantly greater knee abduction angles are observed in patients after ACL reconstruction during the DVJ task, even 2 years post injury (Goerger et al., 2014). The DVJ has also been shown to detect asymmetry and aberrant movement patterns (Paterno et al., 2010), loading rates and force attenuation (Paterno et al., 2010, Paterno et al., 2007), after ACL reconstruction. The DVJ may also enable evaluation of progress in later-phase rehabilitation after ACL reconstruction (Gagnon et al., 2017, Myer et al., 2006, Paterno et al., 2007).

Reliability of landing biomechanics during the DVJ in young healthy participants has been reported (Ford et al., 2007). Between-session intraclass correlation coefficients (ICC) of joint angles (peak and initial contact) and moments (peak) for the sagittal plane (knee flexion) were 0.616, 0.404, and 0.843, and for the frontal plane (knee abduction) were 0.855, 0.864, and 0.870, respectively. The DVJ is recommended as an objective task in the later phase of ACL reconstruction rehabilitation to help evaluate progress and determine readiness for safe return-to-sport (Myer et al., 2006). To confidently use the DVJ in this manner, information about its measurement properties is necessary in this population. Test-retest reliability (including minimal detectable change) and sensitivity to change would provide researchers and clinicians greater ability to measure progress in DVJ performance over time during rehabilitation.

We are unaware of any previous studies that investigated the measurement properties of DVJ landing biomechanics after ACL reconstruction. The objectives of this study were therefore to 1) estimate the test–retest reliability, and 2) explore longitudinal validity of selected lower limb biomechanics assessed during a DVJ completed by patients undergoing rehabilitation after ACL reconstruction.