Generalized Joint Hypermobility Is Predictive of Hip Capsular Thickness

BACKGROUND: The pathomechanics of hip microinstability are not clearly defined but are thought to involve anatomical abnormalities, repetitive forces across the hip, and ligamentous laxity. PURPOSE/HYPOTHESIS: The purpose of this study was to explore the relationship between generalized joint hypermobility (GJH) and hip capsular thickness. The hypothesis was that GJH would be predictive of a thin hip capsule. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A prospective study was performed on 100 consecutive patients undergoing primary hip arthroscopy for the treatment of hip pain. A Beighton test score (BTS) was obtained prior to each procedure. The maximum score was 9, and a score of ≥4 was defined as hypermobile. Capsular thickness at the level of the anterior portal, corresponding to the location of the iliofemoral ligament, was measured arthroscopically using a calibrated probe. The presence of ligamentum teres (LT) pathology was also recorded. RESULTS: Fifty-five women and 45 men were included in the study. The mean age was 32 years (range, 18-45 years). The median hip capsule thickness was statistically greater in men than women (12.5 and 7.5 mm, respectively). The median BTS for men was 1 compared with 4 for women (P < .001). A statistically significant association was found between BTS and capsular thickness; a BTS of <4 is strongly predictive of having a capsular thickness of ≥10 mm, while a BTS ≥4 correlates with a capsular thickness of <10 mm. There was a statistically greater incidence of LT tears in patients with a capsular thickness of ≤7.5 mm and a BTS of ≥4 (P < .001). CONCLUSION: Measurement of the GJH is highly predictive of hip capsular thickness. A BTS of <4 correlates significantly with a capsular thickness of ≥10 mm, while a BTS ≥4 correlates significantly with a thickness of <10 mm.