Does Distance Hide Asymmetry in Jumping Tests Post-ACL Repair?

Return to sport from an ACL repair is an area we can always do better, especially considering current re-injury rates. Because there will NEVER be just ONE superior, cookie-cutter program to run everyone through, you need to remain adaptable.

There’s a bunch of protocols out there; most agree on the jump testing (single hop for distance, triple hop, timed jump, crossover), strength tests, and hitting the 9 month mark as a baseline for return to sport. While I think all of these provide value and use them myself, they certainly don’t classify as enough for what I’m looking for (more on that later).

There was a recent study that examined the single leg hop for distance and questioned it’s use in determining RTS (or at least its intended use). The researchers had participants who were already cleared for return to sport perform a single leg jump for distance and gathered lower limb and trunk kinematics.

Here’s what they found:

⇒ Hop distance was determined 90% by hip and ankle.

⇒ Symmetry in work done by the knee is 69% in propulsion, 81% in landing, even though they measured 97% in distance.

⇒ In order to reduce loading of the knee, the injured side led to increased hip flexion, anterior pelvic tilt, and trunk flexion, with a decrease in knee flexion.

⇒ Conclusion – “Symmetry in performance on a 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.”

This is one of those studies that shouldn’t surprise you, it’s common sense. If you’ve ever had someone perform any of the single leg jump tests, you likely recognize that there’s many ways people will accomplish this task (some prettier and more fluid than others). The issue is that most clinicians/athletes/coaches are focused simply on the distance and don’t watch how the movements are executed.

The fact that our brain found these movement solutions is pretty damn cool though. Without you having to think about a single thing, your brain knows to shift more work to the hip for the propulsion/landing, lean your trunk forward more to cope, and shift stress on the landing to protect the knee joint. So while you might see it as, “asymmetry,” “faulty,” or a “bad landing,” I see it as fucking incredible! Perception…

Where to From Here?

So this goes back to what I was talking about earlier. You cannot rely on just these tests. After all, you aren’t clearing them to go back to a single leg jump for distance event, you are clearing them to return to a chaotic, multi-directional, fatigue-laden sport with endless reactive and dynamic movements. 

I have always used the single leg jump for distance, and still will, but I also use single leg vertical jumps (jump mat) and different depth jump variations. Broad jumps are more hip dominant in the first place, so you should have been using some sort of vertical jump test anyway. Most importantly, I watch these takeoffs/landings AND watch them perform drills in their sport.

If you’ve been doing this long enough, you know that with everything new you learn, comes even more questions. Here’s what I was left thinking…

• How long does this compensation last post-repair? Is it forever? 2 years? 3?
• Does this mean the knee “isn’t ready?”
• Is rehab really about the knee or the nervous/movement system as a whole?
• If those clearing all the RTS tests only had a 5% re-injury rate (Krytsis, 2016), but likely demonstrated these same compensations, are they meaningful?

*Here’s an earlier article on ACL Repair – Read Here