Validity and reliability of the Low Flexion measurement for posterior glenohumeral joint capsule tightness

Posterior shoulder tightness is a problem in many patients with shoulder pain. Tightness manifests as decreased range of motion (ROM) caused by loss of posterior capsule or posterior shoulder muscle flexibility. The posterior capsule often loses flexibility in throwing athletes and may also be present in patients with impingement symptoms. A valid and reliable measurement of posterior capsule tightness is critical to making informed decisions about interventions to improve capsule flexibility. Low Flexion (LF) is a new test shown to be valid for assessing change in posterior capsule flexibility. This report describes three independent projects used to evaluate validity and reliability of LF to determine its clinical usefulness. In Study 1, overhead athletes (n = 13) were compared to non-overhead athletes (n = 13) to examine content validity, and in Study 2 pitchers (n = 18) were measured before and after throwing to assess the stability of LF. T-tests were used to compare mean LF in both analyses. In Study 3 patients receiving rehabilitation (n = 25) were measured twice bilaterally by a single rater to estimate overall reliability and reliability in those with shoulder pain (n = 19) using ICC(3,1) and standard error of measurement (SEM). The overhead athletes had dominant arm deficits in LF that were statistically different than the non-overhead athletes, but LF was not significantly different after throwing. Intraclass correlation coefficients (ICCs) were all above 0.90 and SEM below 3.0°. The Low Flexion test is shown to have acceptable content validity and excellent intra-rater reliability and can be used clinically by one rater to assess posterior capsule tightness.