Single Leg Hop Test: the key functional test for return to sport after ACL injury

After months of rehab following an anterior cruciate ligament (ACL) tear, the million-dollar question shows up: are you ready to go back to training at full intensity? That's where single leg hop tests come in — one of the most widely used tools for making that call based on data, not just gut feeling.

What does this test measure?

The hop test measures horizontal single-leg jump distance, comparing the operated/injured limb with the healthy one through the Limb Symmetry Index (LSI). The idea is simple: if your injured leg can jump as far as the healthy one, that's one sign (among others) that strength, power, and confidence have recovered.

There are several variants (single hop, triple hop, crossover hop, 6-meter timed hop), but the single hop for distance is the most commonly used starting point.

Equipment needed

• Clear space on a non-slip floor (at least 3-4 meters of runway)
• Measuring tape or marked tape on the floor
• Optional: stopwatch (for timed variants)

Test protocol

1. The athlete stands on one leg, with their toes right at the starting line
2. Ask them to jump forward as far as possible on that leg, pushing off and landing on the same leg, holding balance on landing (no extra steps, no support from the other leg)
3. Measure the distance from the starting line to the heel contact point on landing
4. Repeat 2-3 times per leg (alternating or always starting with the healthy leg) and keep the best valid attempt for each side
5. Calculate the LSI: (injured leg distance / healthy leg distance) × 100

Common mistakes

• Accepting attempts where the athlete loses balance or takes an extra step on landing (these are invalid)
• Not standardizing footwear or surface across assessments (affects comparability)
• Running the test too early in rehab, before the athlete has the necessary base strength, which can cause fear or overload

How to interpret the result

LSI (affected leg vs. healthy leg)	Interpretation
≥ 90%	Good symmetry level — typically considered a favorable criterion for progressing toward return to sport (along with other criteria)
80-89%	Moderate symmetry — keep working on leg-specific strength and power before progressing
< 80%	Significant asymmetry — prioritize unilateral strength/power work before moving to higher-demand tasks

Important: the LSI is one criterion among several, not the only one. Return to sport after an ACL injury should be based on a battery of tests (strength, other hop tests, psychological confidence questionnaires) and the clinical team's judgment — not a single number.

Relationship with other tests

The hop test is usually interpreted alongside:

• Lachman Test — to confirm structural stability before progressing functional load
• Pivot Shift Test — assessment of rotational instability, complementing strength and jump data

Tracking LSI month to month

Calculating LSI by hand every time you run an assessment is tedious, and comparing values from three months ago with current ones means digging through loose papers or spreadsheets. With Movalytics you can log the jump distances for each leg, and the app automatically calculates the symmetry index and shows you its evolution throughout the rehab process, with charts ready to share with the athlete or the medical team.

Frequently asked questions

When can a hop test be done after an ACL injury? Only once the athlete has enough strength, range of motion, and impact tolerance (typically in the later stages of rehab), and always under the judgment of the rehab team. Does a 90% LSI mean I can compete without risk? Not on its own. It's a good indicator within a broader set of criteria (strength, other hop tests, psychological factors), not an absolute guarantee against re-injury risk. Why are several types of hop tests used instead of just one? Because each variant (single, triple, crossover, timed) demands different qualities (power, lateral control, endurance), and an athlete may show good symmetry on one and worse on another.