Sports Med U | Educating Minds, Elevating Potential

How limb dominance influences limb symmetry in ACL patients: effects on functional performance

Zumstein, F., Centner, C. and Ritzmann, R., 2022. How limb dominance influences limb symmetry in ACL patients: effects on functional performance. BMC Sports Science, Medicine and Rehabilitation, 14(1), p.206.

In today’s letter

• Overview of how limb dominance effects knee strength after ACL reconstruction

• A fun infographic for you to save and use in the future

• Rapid Results =

Patients who injure their dominant leg tend to have higher LSI scores for knee extension compared to those with non-dominant leg injuries, likely due to the dominant leg’s naturally greater baseline strength. However, this effect does not seem to impact hamstring strength or functional hop tests.

• 3 resources to check out to further your knowledge about limb dominance

• Meme of the week: Umm, thats a little rude 😄 ⏰

Aim of the study

This study aimed to explain how limb dominance shapes the symmetry of functional movements (measured by the Limb Symmetry Index, or LSI) in athletes recovering from ACL surgery, specifically when they’re cleared to return to sport—around nine months post-surgery.

 ACL Injuries Are Common

An anterior cruciate ligament (ACL) injury is a common knee injury, especially in sports requiring sudden stops, pivots, or jumps. The ACL contributes significantly to knee stability, and injuries can cause swelling, and instability.

Studies show that female athletes are up to five times more likely to sustain an ACL injury than male athletes.

While some cases can be treated with rehabilitation, complete tears often require surgery and extensive recovery.

The primary aim of rehab is to help athletes return to sport safely while reducing the risk of reinjury, and this study gives important information into factors that should be considered during recovery when it comes to limb dominance.

Limb Dominance and Recovery

The study confirms that understanding limb dominance in ACL recovery is very important, especially when evaluating quadriceps strength. The findings show that patients who injure their dominant leg tend to have higher Limb Symmetry Index (LSI) scores for knee extension compared to those with non-dominant leg injuries.

This occurs because the dominant leg typically starts stronger, and even if some strength is lost after the injury, the dominant leg's baseline strength masks the deficits, leading to inflated recovery scores.

On the other hand, when the non-dominant leg is injured, its lower starting strength makes deficits more apparent, resulting in a lower LSI score.

In a nutshell,

It’s importnat to factor in limb dominance when interpreting LSI scores to ensure a more accurate assessment of recovery progress. Without considering this, patients may be cleared for return to sport prematurely, raising the risk of reinjury.

Quad Strength is Critical for Functional Recovery

Another key takeaway from the study is the relationship between quadriceps strength and functional performance.

For every 1% increase in quad LSI, hop test symmetry improved by 0.3–0.4%. We all know that the quads are the main focus during knee rehab and especially ACL rehab.

But let me just reinforce one more time just how crucial quadriceps strength is for performing multi-joint movements like jumping and landing.

Restoring quadriceps strength is essential for regaining functional symmetry, and failure to do so can impair balanced movement patterns, ultimately increasing the risk of reinjury (a big no no).

Gender Doesn’t Change the Equation

The study also found that gender does not appear to influence limb dominance patterns or recovery outcomes.

Whether the patient is male or female, limb dominance metrics and recovery trends remained consistent across the board.

This may be a bit surprising for some as there is the assumptions about sex differences in recovery. its importnat to focus on individual strength baselines instead of relying on broad sex-based expectations during rehab.

Clinical Tip

Be mindful of limb dominance when interpreting Limb Symmetry Index scores.

Patients who injure their dominant leg may have higher LSI scores for knee extension due to the dominant leg’s naturally stronger baseline.

This can lead to an overestimation of recovery progress, as strength deficits may be masked.

In contrast, non-dominant leg injuries may show more significant deficits, leading to a potentially lower LSI score.

Therefore, aim for adjusted baselines

Use a higher target of 95% LSI for dominant limb and a slightly lower threshold of 85% for non-dominant to reflect realistic recovery expectations. This prevents overestimation of functional readiness.

Top 3 Resources to Check Out

And learn more about ACL rehab

1. ACL Rehab guide 2.0 (PDF) - LINK

2. How to rehab ACL’s - Step-by-step (Article) - LINK

3. ACL rehab webinar

Meme of The Week

When You’re Ready to Learn More

We have great resources for you to devourer

1. Killer Articles —> Literally everything you need to know about a specific injury

2. Tendinopathy 4 phase rehab frame work - My book that walks you through a step by step process of treating tendons

Thank you for reading this weeks edition!

Have a browse through our articles to sharpen you diagnostic skills