Tuck Jump Assessment: A 10-Point Screening Protocol for ACL Injury Risk

A high-school volleyball player warms up clean, gets through two sets without a hitch, then on a routine landing her knee caves inward and she's on the floor. Nothing about the play looked dangerous going in. That's the frustrating part of most non-contact ACL tears — the landing that ends a season usually looks like the hundred landings before it, except for a knee drifting a few extra degrees inward each time. Coaches without a motion-capture lab can't measure that drift directly, but they can see it, if they know where to look.

The tuck jump assessment (TJA), developed at the Cincinnati Children's Sports Medicine Biodynamics Center, gives coaches a 10-second, equipment-free window into the movement pattern most tied to ACL injury risk. This guide covers the setup, the 10-item scoring checklist, how to read the score without overclaiming precision, and where an IMU-based jump monitor adds numbers the eye alone misses.

The TJA grew out of a lab finding, not a stand-alone idea. Hewett and colleagues (2005) put 3D motion capture on 205 female athletes across a season and tracked who went on to tear an ACL. Nine did. The variable that separated the injured group most cleanly was peak knee abduction moment during a drop-vertical-jump landing: athletes who later ruptured their ACL had loaded their knees into valgus with meaningfully higher moments, and a cutoff near 25 Nm classified injury status with roughly 78% sensitivity and 73% specificity in that sample.

That's a strong signal, but it needs a force plate and 3D camera array to measure — equipment most club programs don't have. Myer, Ford, and Hewett (2008) built the tuck jump assessment as a field-usable proxy: a task that reproduces the same valgus-loading pattern, scored visually against 10 criteria instead of with force sensors. It's a translation of a lab-grade finding into a sideline tool, not a separate discovery — worth remembering when interpreting what a TJA score can and can't tell you.

Part of the appeal of the TJA is how little it demands: a smartphone camera capable of at least 120 fps slow-motion capture, a 2m by 2m clear floor space on a firm surface, and two camera angles — one frontal, one sagittal from the side. Skip the frontal angle and you'll miss the single highest-value criterion, knee valgus.

Footwear should match what the athlete competes in — unfamiliar shoes distort a future retest. Warm up with five minutes of light movement and a few submaximal jumps first; a cold first attempt looks worse than the real baseline.

The test itself is short, which is the point — repeatable in a few minutes at the start or end of a session.

1. Position the cameras. Frontal camera 2-3m from the athlete at hip height; sagittal camera at the same distance and height, 90 degrees to the side.
2. Cue the movement. Bend the knees and hips into a quarter-squat, jump straight up while pulling both knees toward the chest at peak height, then land and immediately jump again — continuous, maximum effort, for 10 seconds.
3. Record two sets. Run two 10-second sets with 30-60 seconds rest between them. One set catches obvious flaws; two let you check whether flaws only appear once fatigue sets in, itself one of the 10 criteria.
4. Score in slow motion. Review at quarter speed or slower. Scoring live is how the subtler criteria — foot contact timing, trunk control — get missed.
5. Log the flaw count. Each criterion is scored present or absent for that set, producing a count of 0 to 10, not a continuous scale.
6. Re-test on a schedule. Every 4-6 weeks during an active correction block, or at minimum pre-season and mid-season.

Each criterion is scored as a binary flaw: present anywhere in the set, or absent throughout. A rep-by-rep tally isn't part of the protocol — what matters is whether the flaw shows up at all across the 10 seconds.

Foot contact timing and pause between jumps are the two raters disagree on most, which matters for how you use the score, covered next. Knee valgus and thigh symmetry, by contrast, tend to get near-unanimous agreement, because the fault is large and visually obvious even to a first-time scorer.

The protocol doesn't publish a validated cutoff that predicts who will tear an ACL — that prospective validation exists for the lab-measured knee abduction moment (Hewett et al., 2005), not for the visual TJA flaw count. Treat the score as a movement-quality flag that tells you who needs correctives first, not a threshold that clears or benches anyone.

Reliability is the other thing to stay honest about. Herrington, Myer, and Munro (2013) had raters score recorded TJA trials from a modest sample of youth athletes, under 20 in the cohort, and found agreement good to excellent for the visually obvious criteria — knee valgus, thigh symmetry — but only fair for criteria depending on precise timing or audio cues, foot contact timing among them. Two coaches watching the same video can land on different counts for those items. Keep the same rater scoring an athlete across retests, and don't weigh a one-point change on a low-reliability criterion too heavily.

Most athletes don't fail all 10 criteria — they fail two or three in a consistent pattern, and the pattern usually points to a specific fix rather than a generic correctives circuit.

• Knee valgus after rep 6 or 7: more a hip-abductor endurance problem than a technique problem. Banded lateral walks and single-leg glute bridges, three times a week for 4-6 weeks, clean this up faster than cueing alone.
• Wide or narrow foot placement: tape a shoulder-width footprint outline on the floor and have the athlete land inside it for 2-3 weeks before retesting — a motor-learning fix, not a strength fix.
• Landing noise paired with a pause between jumps: these travel together and point to poor eccentric strength. Add tempo landings — a 3-second eccentric lowering from a low box — before reintroducing continuous rebound jumps.
• Trunk lean or rotation: cue chest tall, ribs stacked over hips, checked with a side-view camera. Usually a bracing-cue gap, not a strength deficit, and it responds within a few sessions.

Retest after 4-6 weeks of work on the two or three criteria that actually showed up, not the full menu for all 10 — spreading a young athlete's limited training time thin dilutes the dose on the flaws that apply to them.