Measurement properties for muscle strength tests following anterior cruciate ligament and/or meniscus injury: what tests to use and where do we need to go? A systematic review with meta-analyses for the OPTIKNEE consensus

Key points

1. 01This is a measurement-properties review (reliability and validity of the tests themselves), not a study of whether any treatment works.
2. 02Across 36 studies and 31 test modes/equipment setups, high-quality evidence for most strength tests was scarce.
3. 03Isokinetic concentric tests on a computerised dynamometer were the best rated, with sufficient intrarater reliability (very low to low quality) and sufficient construct validity (moderate quality).
4. 04Isotonic 1RM tests on a seated leg-extension and prone leg-curl machine had high-quality evidence of sufficient criterion validity (r = 0.91 and r = 0.80 vs the isokinetic gold standard), making affordable weight machines a good alternative.
5. 05Isometric handheld dynamometry had sufficient intrarater reliability only with one experienced rater and standardized setup, but insufficient construct and criterion validity (high quality), so its results should not be used interchangeably with isokinetic results.

How it was conducted

Design

Systematic review with meta-analyses using the COSMIN Risk of Bias checklist and modified GRADE; PRISMA-reported, OSF-registered

Search

Medline, Embase, CINAHL, SPORTDiscus from inception to 5 May 2022; 3533 records, 36 studies included (year 2000 onward, English only)

Participants

Individuals with ACL injury and/or isolated meniscus injury, mean injury age <=30 years (28 ACLR, 3 ACL-injured, 4 pre/post-ACLR, 1 meniscectomy)

Outcomes

Measurement properties (reliability, measurement error, construct validity, criterion validity) of 31 knee extensor/flexor strength test setups

Analysis

Random-effects pooling of correlation coefficients via Fisher Z (construct validity); 'worst score counts' RoB; '+/-/?' rating per COSMIN

What they found

• Reliability: isokinetic concentric extensor at 60 deg/s showed sufficient intrarater reliability (ICC 0.95); isometric extensor via HHD sufficient intrarater (ICC 0.91 to 0.98) but insufficient interrater (ICC 0.43 to 0.60).
• Measurement error: all rated indeterminate because no minimal important change (MIC) value was defined; isokinetic CV was 2.9% to 8.3% (extensor) and 3.3% to 3.4% (flexor).
• Construct validity: isokinetic concentric high-speed extensor correlated strongly with hop tests (r = 0.72) and moderately with patient-reported outcomes (r = 0.38), rated sufficient at moderate quality; isokinetic slow-speed and isometric flexor rated insufficient.
• Criterion validity vs isokinetic gold standard: isotonic 1RM extensor r = 0.91 and flexor r = 0.80 (sufficient, high quality); isometric HHD extensor r = 0.62 and LSI r = 0.17 to 0.52 (insufficient, high quality).
• Only four measurement properties were studied, with none assessing responsiveness or interpretability; high quality of evidence could rest on a single study under COSMIN rules.

Limitations

• Overall paucity of evidence, with reliability and measurement-error data coming from very few, often small studies.
• Under COSMIN/GRADE rules a high quality-of-evidence rating can rest on a single study (imprecision only downgraded below n = 100).
• Inclusion was restricted to mean injury age <=30 years and to studies from 2000 onward, and isolated meniscus injury was represented by only one study.
• No measurement-property evidence was found for responsiveness or interpretability, and MIC values for these tests are not established.

Why it matters

For patients

The accuracy of the strength test your clinician uses to track your ACL or meniscus recovery varies, and the better-supported tests give a more trustworthy picture of your progress.

For clinicians

Prefer isokinetic concentric testing where available, use isotonic 1RM on weight machines as a good affordable alternative, and treat isometric handheld results cautiously and not interchangeably with isokinetic results.

For readers

Most knee strength tests used after ACL or meniscus injury lack high-quality validation, with isokinetic concentric and isotonic 1RM the best supported.