Generalized joint hypermobility subjects without knee hyperextension have greater walking anterior tibial translation and flexion angle than those with knee hyperextension

Background: The walking knee kinematic results of generalized joint hypermobility (GJH) subjects were controversial in previous studies. We proposed that this could be related to the knee statuses of GJH subjects with/without knee hyperextension (KH) and assumed that there are significant sagittal knee kinematic differ-ences between GJH subjects with/without KH during gait. Research question: Do GJH subjects with KH exhibit significantly different kinematic characteristics than those without KH during walking?Methods: 35 GJH subjects without KH, 34 GJH subjects with KH, and 30 healthy controls were recruited in this study. A three-dimensional gait analysis system was used to record and compare the knee kinematics of the participants.Results: Significant walking knee kinematics differences were found between GJH subjects with/without KH during walking. GJH subjects without KH had greater flexion angles (4.7-6.0 degrees, 24-53 % gait cycle (GC), p < 0.001; 5.1-6.1<degrees>, 65-77 % GC, p = 0.008) and anterior tibial translation (ATT) (3.3-4.1 mm, 0-4 % GC, p = 0.015; 3.8-4.3 mm, 91-100 % GC, p = 0.01) than those with KH. Compared to controls, GJH without KH exhibited increased ATT (4.0-5.7 mm, 0-26 % GC, p < 0.001; 5.1-6.7 mm, 78-100 % GC, p < 0.001), and range of motion of ATT (3.3 mm, p = 0.028) whereas GJH with KH only exhibited increased extension angle (6.9-7.3 degrees, 62-66 % GC, p = 0.015) during walking.Significance: The findings confirmed the hypothesis and suggested that GJH subjects without KH had more walking ATT and flexion angle asymmetries than those with KH. This may raise concerns about the differences in knee health and risk of knee diseases between GJH subjects with/without KH. However, further investigations should be done to explore the exact influence of walking ATT and flexion angle asymmetries in GJH subjects without KH.