Differences in the collagen of semitendinosus tendon in patients with and without general joint laxity

Aims Generalized joint laxity (GJL) has been reported to be a risk factor for anterior cruciate ligament (ACL) graft injury. There are no reports of differences in the collagen content of semitendinosus tendons used as graft tendon being a risk factor for ACL graft injury. The aim of this study was to determine the differences in the collagen type content in the semitendinosus tendon in patients with and without GJL. Methods In total, 36 knees from 36 patients who underwent ACL reconstruction were analyzed. GJL was assessed using the Beighton score, with GJL defined as a Beighton score of ≥ 4, ≥ 5, or ≥ 6. The patients were divided into two groups: those with GJL (G-group) and those without (N-group). The parameters included the quantification of collagen types I, III, V, and XII in semitendinosus tendons via immunohistochemical staining, alongside preoperative radiological evaluation of the knee joint laxity. Comparisons were made between the two groups, and the correlation between the Beighton score and collagen content was analyzed. Results There were significant differences between the G-group and the N-group in the type III collagen content (117.9 (SD 17.4) vs 130.0 (SD 11.5), p = 0.036) and the joint line convergence angle (JLCA) under varus stress (6.3° (SD 1.9°) vs 4.6° (SD 2.0°), p = 0.021) only when a Beighton score of ≥ 6 was defined as GJL. Hyperextension of the knee under anaesthesia differed significantly between the two groups across all definitions of GJL. The Beighton score was significantly correlated with the type III collagen content ( r = 0.375, p = 0.024). Conclusion Patients with GJL exhibited significantly higher collagen type III content in the semitendinosus tendon compared to those without GJL. Cite this article: Bone Joint Res 2026;15(10):1228–1235.