Hop Testing: Looking Beyond Limb Symmetry Index (LSI)

This brilliant and recent article by Rush et al (2024) highlights the importance of analysing take-off mechanics during single-leg hop tests (SLHD) for patients recovering from anterior cruciate ligament reconstruction (ACLR).

Traditionally, focus has been placed on hop distance and symmetry between limbs or LSI.

However, this study suggests that how patients generate movement during take-off provides crucial information about quadriceps function and potential compensatory strategies that may put them at risk of further injury - most commonly, their currently healthy, uninjured limb.

Key Takeaways for Physios:

• Knee Underloading: Patients with ACLR may exhibit lower peak knee flexion angles, moments, and power absorption during take-off compared to the uninvolved limb and healthy controls. This suggests the quadriceps may not be fully recovered or patients may be avoiding knee flexion to compensate for weakness.
• Quadriceps Strength Matters: Lesser quadriceps strength symmetry is associated with altered take-off mechanics, including reduced knee loading and potentially greater trunk flexion to shift the center of mass and help them jump/hop easier.

Incorporating These Findings into Practice:

• Include looking at take-off mechanics either by force plate or video analysis during single leg hop assessments for ACLR patients.
• Develop rehabilitation programs that address quadriceps weakness (especially in isolation) and any compensatory strategies identified during take-off analysis.
• Don't assume that the person has a strong quad with they can single leg squat or single leg leg press a heavy load - ACLR patients are great at cheating through the hip during "functional" tasks.
• Train patients to properly load the involved knee during single-leg exercises to prepare them for more demanding activities.

By targeting the quad in rehab and taking a more comprehensive approach to hop testing evaluation, physiotherapists can gain valuable insights into how ACLR patients generate movement and develop more effective rehabilitation strategies to optimise long-term joint health and function.

Take a deep dive into the full text paper here

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