Lower limb biomechanics after an ACL reconstruction
This is a summary of the insights from the research paper "Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?".
Is the symmetry index for the single leg hop for distance test enough to actually assess symmetry in lower limb biomechanics after an ACLR? 🤔
ℹ️ In the regularly used hop test battery, the Limb Symmetry Index (LSI) of >90% in distance hopped is recommended as a cut-off point for safe RTS.
ℹ️ The use of this >90% LSI threshold for functional hop tests has previously been questioned because of the potential risk of masking information about movement deficits and different strategies employed.
➡️ Researchers captured video-based 3D motion and EMG in 26 athletes after ACLR and 23 healthy controls during single leg hop for distance (SLHD) and calculated lower limb and trunk kinematics.
🧠 Symmetry in performance on an SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function
- Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%.
- During landing, the operated knee absorbed less work than the unoperated knee.
- During landing, the uninjured knee is loaded more heavily compared with the knees of uninjured athletes, which might explain the increased rates of contralateral injuries.
- Athletes after ACLR compensated for the lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvic tilt, and trunk flexion.
❗ In the Hylyght platform, the hop test battery and validated psychological questionnaires (e.g. the Tampa scale of kinesiophobia) are included in our return to sport protocols after an ACL reconstruction. We’re also working on automated video analysis to assess angles of hop & jumping tests in a time-efficient manner.