14.2 Functional Testing & Return-to-Play Criteria

Quick Answer: Return-to-play (RTP) is not a single hop. Use a battery: single hop, triple hop, crossover hop, 6-m timed hop, plus Y-Balance/SEBT, strength (isokinetic if available), movement quality, and psychological readiness (ACL-RSI). LSI of about 90% is a commonly cited threshold with caveats — the uninvolved limb may be deconditioned. Shared decision-making with the physician, athlete, and family; the physician often holds medical authority; the AT documents criteria. Trap: returning because 'the season starts Friday' with ~70% LSI and kinesiophobia.

PA8 Domain IV, task 0406, asks the AT to determine functional status and readiness to return to activity. Functional status is a cluster, not a vibe and not a date on the protocol sheet: range of motion, effusion, strength, hop battery, movement quality, sport-specific tests, patient-reported outcomes, psychological readiness, and time from injury or surgery. The clinic hop that 'looked pretty good' on Monday is not a Friday night starting assignment.

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Not a single hop: the Noyes battery and friends

The classic lower-extremity hop battery (Noyes, Barber, and Mangine, American Journal of Sports Medicine 1991) is four tests, usually the involved limb compared with the uninvolved:

1. Single hop for distance — one maximal hop, stick the landing (typically a controlled hold on the order of 2 seconds). Measure from a consistent landmark (commonly the takeoff line to the landing heel).
2. Triple hop for distance — three consecutive hops for maximal distance; stick the last landing.
3. Crossover hop for distance — three consecutive hops crossing a midline strip (often about 15 cm), maximal distance.
4. 6-meter timed hop — hop 6 m as fast as possible. Time is the score; lower is better.

Allow practice trials, then average or take the best of a small number of recorded trials per the clinic's protocol, and watch how they land, not only how far. A long hop with a valgus crash is a failed test even if the tape measure is flattering.

Limb symmetry index. For distance hops, LSI = (involved / uninvolved) × 100. For the timed hop, faster is better, so LSI is typically (uninvolved time / involved time) × 100 — invert the ratio so a slower involved limb still scores below 100%. Mixing the formulas is a practical error: an involved timed hop that is slower must not be reported as 'better than the other side' because you divided the wrong way.

About 90% LSI on hop and strength tests is the commonly cited 'pass' threshold in ACL RTP literature (Reid and colleagues; Munro and Herrington; many subsequent batteries). Teach ~90% as a commonly cited threshold, not a biological law. Healthy uninjured athletes often sit near 100%. A systematic review line of work has also shown that passing LSI ≥90% on a hop battery does not reliably predict who will sustain a second ACL injury. Distance can pass while knee flexion, valgus, and trunk lean still fail. Do not invent a stricter numeric cutoff (95%, 97%) as if it were a NATA rule — some clinicians argue for higher targets because 'normal' is near 100%, but the number you must be able to source and caveat on the exam is ~90%.

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LSI caveats: the uninvolved limb is not a gold standard

After ACL injury and ACLR, both limbs often decondition. Comparing a weak involved side to a deconditioned uninvolved side inflates LSI and overestimates function (Wellsandt, Schmitt, and related work). A 92% LSI on a triple hop where both distances are poor for that athlete's sport is not clearance. Better anchors when you have them: preinjury scores, age/sex/activity norms, or estimated preinjury capacity. If the 'good' leg hopped like a deconditioned teammate, 90% of that number is still a problem.

Time and criteria together. Grindem and colleagues (Delaware-Oslo ACL cohort, British Journal of Sports Medicine 2016) associated earlier return to level-1 sport, especially in the window before about 9 months, with higher reinjury risk, and associated passing strength, hop, and patient-reported criteria with lower risk. Kyritsis and colleagues (BJSM 2016) found athletes who failed a discharge battery (including isokinetic strength and hop tests) had a substantially higher graft-rupture rate (on the order of four times in that cohort). Neither paper makes '90% at 6 months' a license to play. Time is not a criterion by itself; criteria without enough healing time are also incomplete. Graft biology, sport demand, and age (adolescents returning to pivoting sport) all argue against calendar-only clearance.

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Strength, Y-Balance/SEBT, and movement quality

Isokinetic testing, when available, remains a useful quadriceps and hamstring snapshot. Quadriceps peak-torque LSI is commonly targeted at ≥90%; a lingering quad deficit is a persistent ACL problem and a reason hops can look better than the knee is. Hamstring capacity and the hamstring-to-quadriceps relationship matter for ACL strain, but do not reduce the whole decision to one ratio. When isokinetics are absent, use handheld dynamometry, repetition-max estimates, or closed-chain strength tests — do not skip strength because hops 'looked fine.' Hops can hide a quad that will not last a second half.

Y-Balance Test / Star Excursion Balance Test (SEBT): dynamic single-leg reach in anterior, posteromedial, and posterolateral directions (Y-Balance) or the fuller SEBT star. Normalize to limb length. Anterior reach asymmetry of more than about 4 cm has been associated with higher lower-extremity injury risk in some basketball cohorts (Plisky and colleagues). Teach that as a research signal, not a universal BOC cutoff. Use the test to find reach deficits and poor control, not to rubber-stamp RTP.

Movement quality is part of the battery even when it is not a numbered LSI: drop vertical jump, tuck jump, lateral shuffle, and cutting video. Dynamic valgus on a drop vertical jump is a classic ACL-prevention and RTP observation (Hewett / Myer line of work). An athlete can hop far with a stiff, upright strategy that will not survive a crowd. Sport-specific tests finish the picture: kicking distance and accuracy, throwing velocity and pain, skating starts, swimming turns — match the sport, the position, and the energy system.

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Psychological readiness: ACL-RSI and kinesiophobia

The ACL-Return to Sport after Injury (ACL-RSI) scale (Webster, Feller, and colleagues) asks about emotions, confidence in performance, and risk appraisal. Low scores associate with not returning to sport and with poorer outcomes; they are data, not softness. Kinesiophobia (often sampled with the Tampa Scale of Kinesiophobia) shows up as a stiff, tentative plant — a functional finding. Graded exposure, honest education about risk, and referral when anxiety or depression is in play are part of RTP, not extras. Do not invent a single ACL-RSI cutoff as a NATA number; use the concept and the trend, and combine it with the physical battery.

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Shared decision-making, authority, documentation, graduated RTP

The RTP decision is not the coach's. Shared decision-making includes the physician, AT, athlete, and family (the coach may contribute logistics — practice schedule, position demand — but does not hold a medical veto). In many secondary-school and college settings the team physician has medical authority for clearance. The AT implements the protocol, collects the battery, documents, communicates, and can withhold participation under standing orders, the injury policy, and the emergency action plan even when a coach is loud. Document: date, tests used, raw scores and LSI values, landing/movement notes, patient-reported and ACL-RSI results, who cleared, and the graduated plan.

Graduated RTP after a lower-extremity reconstructive or high-demand injury is not clinic → championship. Typical steps: controlled non-contact practice (individual skill, no opponent) → contact practice or scrimmage → unrestricted competition. Passing a hop battery on Monday does not mean starting in the state final on Friday. Volume, intensity, and opposition are separate progressions. The athlete who 'passed' in sneakers on a clean floor still has to survive sport footwear, a live defender, and fatigue.

Exam trap: returning because 'the season starts Friday' with about 70% LSI and kinesiophobia. Calendar pressure is not a criterion. Seventy percent LSI is not 'close enough.' Fear that makes the athlete hesitate on a plant is a reason to delay and treat, not a reason to tape and hope. Ninety percent of a deconditioned uninvolved limb plus a pretty single hop plus a coach's deadline is still not a battery.