Reliability and validity of observational risk screening in evaluating dynamic knee valgus

Nonexperimental methodological study.

To determine the interrater and intrarater reliability and validity of using observational risk-screening guidelines to evaluate dynamic knee valgus.

A deficiency in the neuromuscular control of the hip has been identified as a key risk factor for noncontact anterior cruciate ligament (ACL) injury in postpubescent females. This deficiency can manifest itself as a valgus knee alignment during tasks involving hip and knee flexion. There are currently no scientifically tested methods to screen for dynamic knee valgus in the clinic or on the field.

Three physiotherapists used observational risk-screening guidelines to rate 40 adolescent female soccer players according to their risk of ACL injury. The rating was based on the amount of dynamic knee valgus observed on a drop-jump landing. Ratings were evaluated for intrarater and interrater agreement using kappa coefficients. Sensitivity and specificity of ratings were evaluated by comparing observational ratings, with measurements obtained using 3-dimensional (3-D) motion analysis.

Kappa coefficients for intrarater and interrater agreement ranged from 0.75 to 0.85, indicating that ratings were reasonably consistent over time and between physiotherapists. Sensitivity values were inadequate, ranging from 67% to 87%. This indicated that raters failed to detect up to a third of "truly high-risk" individuals. Specificity values ranged from 60% to 72%, which was considered adequate for the purposes of the screening.

Observational risk screening is a practical and cost-effective method of screening for ACL injury risk. Rater agreement and specificity were acceptable for this method, but sensitivity was not. To detect a greater proportion of individuals at risk of ACL injury, coaches and clinicians should ensure that they include additional tests for other high-risk characteristics in their screening protocols.