The ACL test that was meant to rule it out

Hi,

This month we move from the neck to the knee, and to a test that has had very good press.

The study: the lever sign, tested properly

The lever sign is simple. With the patient supine, place a fist under the upper calf and press down on the lower thigh. If the heel stays on the bed, the ACL is suspect. Early reports were near perfect, and a 2022 pooled analysis put its LR+ near 10 and its LR− at 0.18 (Sokal 2022), though other reviews put its LR+ as low as 3.2. It became the favoured test for ruling a tear out.

Norris and colleagues (2025) tested it more carefully (several of them also wrote the 2022 review). They studied 101 consecutive adults from a hospital acute knee injury clinic, all more than three weeks (on average about three months) after a traumatic knee injury. Just over half (53, or 52.5%) had a full-thickness ACL tear on MRI. Two physiotherapists did the test on both a firm and a soft surface; one of them was blinded to all clinical information and to the MRI.

• Best result (unblinded tester, firm surface): LR+ 3.02 and LR− 0.53. On the soft surface, the best LR− was 0.45.
• Blinded tester, firm surface: LR+ 1.27 and LR− 0.93. That's close to useless.
• Agreement between testers: only moderate (kappa 0.53, soft surface).
• Fist position mattered: between 47% and 81% of results changed (depending on tester and surface) when the fist was moved roughly 55 mm along the calf.

At the bedside: a negative lever sign does not rule out an ACL tear. Say you put the chance of a tear at about three in ten before testing: even the best-case negative (LR− 0.45) only brings that to about one in six, and the blinded tester's negatives (LR− 0.60 on the soft surface, 0.93 on the firm) leave it at about one in five or higher (we calculate). Treat it as a weak extra finding, not a screen.

Caution: one centre, patients tested weeks after injury rather than in the first days, and partial tears excluded. It may behave differently in a freshly injured knee.

Test of the month: the Lachman test

What it asks: is the ACL torn?

How: knee in 20–30° of flexion, patient relaxed. Stabilise the thigh with one hand and draw the upper tibia forward with the other. Compare with the other knee.

Positive: more forward movement than the other side, with a soft or absent end-feel.

The numbers (Sokal 2022, pooled across studies; the review's bivariate-model estimate): sensitivity 81%, specificity 85%, LR+ 5.72 and LR− 0.24.

What that means in the room (we calculate). Say the history makes a tear about as likely as not: a positive Lachman makes it very likely (about 85%), but a negative still leaves about one chance in five. In full:

Starting at 10%: a positive Lachman takes you to about 39%; a negative, about 3%.
Starting at 30%: positive about 71%; negative about 9%.
Starting at 50%: positive about 85%; negative about 19%.

The catch: the review found older reviews had overestimated the Lachman, and it was less accurate more than three weeks after injury (sensitivity 70%); a swollen, guarded knee makes it harder to do. A negative in a very likely tear still leaves a real chance.

A or B? Medial knee pain after a twist: MCL, meniscus, or both?

Both injuries give pain on the inside of the knee, and they often happen together. Where it's tender does a lot of the separating.

• Tenderness along the ligament, above or below the joint line, points to the MCL.
• Tenderness at the joint line itself points to the meniscus.

Joint line tenderness for a meniscal tear (Meserve 2008, pooled across studies): sensitivity 76% and specificity 77%, which works out at LR+ about 3.3 and LR− about 0.31 (we calculate). Say you think a meniscal tear is about as likely as not: tenderness at the joint line takes that to about three in four, and no tenderness brings it down to about one in four (we calculate). A weak test on its own.

Caution: because the two injuries so often occur together, finding one doesn't rule out the other.

Famous but feeble: a negative pivot shift

The pivot shift is excellent when it's positive (pooled LR+ 10.7), but it misses nearly half of tears (sensitivity 55%), so its negative is weak: LR− 0.48, only just better than the 0.5 we use as the line for a test of limited value (Sokal 2022). From the review's own starting point of 36%, a negative still leaves about a one-in-five chance of a tear (we calculate). Use it to rule in, never to reassure.

One thing to do on Monday

After a twisting knee injury with a pop, rapid swelling or giving way, do a Lachman on both knees, record the end-feel, and don't let a negative lever sign or pivot shift clear the ACL on its own.

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Sources

1. Norris R, Price A, Byrne J, et al. The lever sign test demonstrates limited clinical utility for diagnosing full-thickness anterior cruciate ligament tears after a traumatic knee injury. Orthop J Sports Med. 2025;13(5):23259671251334775. doi:10.1177/23259671251334775
2. Sokal PA, Norris R, Maddox TW, Oldershaw RA. The diagnostic accuracy of clinical tests for anterior cruciate ligament tears are comparable but the Lachman test has been previously overestimated: a systematic review and meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2022;30(10):3287–3303. doi:10.1007/s00167-022-06898-4
3. Meserve BB, Cleland JA, Boucher TR. A meta-analysis examining clinical test utilities for assessing meniscal injury. Clin Rehabil. 2008;22(2):143–161. doi:10.1177/0269215507080130

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Rule It In is published by Trokos (a registered business name of Trokos Health Pty Ltd, ACN 703 339 897, ABN 97 703 339 897; PO Box 6004, Meridan Plains QLD 4551, Australia) and written by Shane Tompson, physiotherapist. It's drafted with AI assistance, and every figure is checked against its source wherever the paper can be obtained. It's for clinicians, and supports but doesn't replace clinical judgement.

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