Hop testing after #ACLR β horizontal (distance) is easier to measure than vertical (height) but are they the same?
(Spoiler: not even close)
Thread π
During a vertical hop, the hip, knee, and ankle contribute almost equally, during push-off (height achieved) and landing (force absorption).
Horizontal hop is very different.
Work during propulsion (=distance achieved): knee contributes only 13% but the landing phase (absorption) is done 2/3 by the knee.
Vertical hop is a better metric to evaluate knee function than horizontal.
Achieving equal hop distance can hide deficits in knee function since distance is mostly achieved from the hip & ankle
We measured athletes after #ACLR during propulsion & landing of a single leg hop for distance after they have been cleared to #RTS
During propulsion symmetry in work done by the knee is only 69% & during landing itβs 81%, despite achieving 97% of hop distance
The relatively large between-leg knee work difference is easy to miss as the knee joint contributes little (12%) to propulsion in a single hop for distance.