Clinimetric properties of the knee extension prone test (KEPT): a new method to assess knee hyperextension deficit

Key points

1. 01The KEPT is proposed as a low-cost, affordable alternative for measuring knee hyperextension deficit.
2. 02Two examiners compared the KEPT against goniometry, inclinometry, and photogrammetry in healthy participants and participants with a history of knee injury.
3. 03Reliability was good within the same examiner and excellent between different examiners.
4. 04Validity against existing measurement methods ranged from moderate to good.
5. 05Measurement error was small within one examiner but larger between examiners.

How it was conducted

Design

Clinimetric study of concurrent validity and reliability

Groups

Group 1, healthy participants; Group 2, participants with a history of knee injury

Examiners

Two examiners performing each evaluation

Comparison methods

Lateral knee goniometry, anterior tibial inclinometry, lateral photogrammetry in supine and prone

Statistics

Pearson correlation (r) for validity; intraclass correlation coefficient (ICC) for reliability

What they found

• Intra-examiner reliability was good (ICC = 0.85, 95% CI 0.75 to 0.89).
• Inter-examiner reliability was excellent (ICC = 0.92, 95% CI 0.88 to 0.94).
• Standard error of measurement was 0.47 degrees intra-examiner and 1.30 degrees inter-examiner.
• Minimum detectable change was 2.35 degrees intra-examiner and 6.5 degrees inter-examiner.
• Concurrent validity ranged from moderate to good (r = 0.54 to 0.78, p < 0.01).

Limitations

• Validity was only moderate at the lower end of the correlation range, so the KEPT does not perfectly match reference methods.
• The exact total sample size and group sizes are not reported in the available text.
• Between-examiner measurement error and minimum detectable change were notably larger than within-examiner values.
• As a single clinimetric study, the findings need replication in broader populations and clinical settings.

Why it matters

For patients

If your clinician checks your knee hyperextension, the KEPT can give a consistent measurement without expensive equipment.

For clinicians

The KEPT offers a valid, reliable, low-cost option for assessing knee hyperextension deficit, with small within-examiner error but a larger 6.5 degree minimum detectable change when different examiners take measurements.

For readers

This study introduces and validates a new simple test rather than evaluating a treatment, supporting its use as a measurement tool.