The effect of lower extremity rotational profile on postural control, muscle strength, functional capacity, and lower extremity function in children with generalized joint hypermobility

Generalized joint hypermobility (GJH) is defined as the excessive range of motion of synovial joints beyond physiological limits. The aim of this thesis was to investigate the effects of lower extremity rotational profile on postural control, muscle strength, functional capacity, and lower extremity function in children with GJH. A total of 48 children aged 7–16 years who voluntarily agreed to participate were included: 16 children with GJH and lower extremity rotational profile abnormalities (GJHrot+), 16 children with GJH but without rotational profile abnormalities (GJHrot−), and 16 healthy controls without GJH and/or rotational profile abnormalities. All participants were initially assessed for GJH using the Beighton score. Following the collection of sociodemographic data, clinical assessments and primary/secondary outcome measures were performed bilaterally on the same day. Clinical evaluations for lower extremity rotational profile included measurements of hip internal rotation (IR) and external rotation (ER) angles, Craig test, thigh-foot angle (TFA), foot progression angle (FPA) and heel bisector line (HBL) test were performed. Q angle, navicular drop test (NDT), ankle dorsiflexion range of motion, and leg length measurements were recorded. Lower extremity muscle tightness/flexibility was assessed using the Silfverskiold test, Popliteal angle measurement, Sit and Reach test, Ober test, Thomas test and Duncan-Ely test were performed. After completing clinical assessments, postural control was evaluated with the Biodex Balance System (BBS), muscle strength was measured using a MicroFET2 digital hand-held dynamometer, functional capacity was assessed via the 6-minute walk test (6MWT), and lower extremity functionality was measured using the Lower Extremity Functional Scale (LEFS). The groups were similar in age, sex, height, weight, and body mass index. The control group had significantly lower Beighton scores compared to both GJH groups (p<0.001), with no difference between GJHrot+ and GJHrot− groups. Hip IR and ER angles and Craig test measurements differed significantly, especially with the GJHrot+ group differing from both control and GJHrot− groups (p<0.001). No significant difference was observed between groups in terms of FTA (p>0.05). FPA showed significant differences between the control group and the GEHrot+ group and between the GEHrot+ and GEHrot− groups on both the right and left sides (p<0.001); there was no difference between the GEHrot− and control groups (p>0.05). No significant differences were observed between groups in terms of HBL for the right and left sides (p>0.05). The Q angle measured in standing was significantly higher in the GJHrot+ group compared to other groups (p<0.001). Additionally, NDT values were significantly different in the GJHrot+ group compared to control and GJHrot− groups (p<0.01), with no difference between GJHrot− and controls. Ankle dorsiflexion angles were significantly higher in both GJHrot+ and GJHrot− groups compared to controls (p<0.05–0.01). Muscle tightness/flexibility tests including Thomas, Duncan-Ely, Ober, Silfverskiold and Sit and Reach tests showed no significant differences among groups (p>0.05), except for Popliteal angle measurements, where the control group had significantly higher values than both GJHrot+ and GJHrot− groups (p<0.01). In Biodex Balance System tests, significant differences were found between the control and GJHrot+ groups in postural stability overall, anterior-posterior, medial-lateral parameters and some stability limits parameters (p<0.05), while no significant difference was observed between the control and GJHrot− groups. Muscle strength measurements revealed significantly lower strength in the right and left gluteus maximus and medius muscles of the GJHrot+ group compared to both control and GJHrot− groups (p<0.05), with no significant differences in other muscle groups. No significant differences were found among groups regarding 6MWT distance and LEFS scores (p>0.05). This study demonstrated that lower extremity rotational profile abnormalities in children with GJH adversely affect postural control and gluteal muscle strength. The similar performance of the GJHrot− group to healthy controls in these parameters suggests that the negative effects are primarily related to rotational profile abnormalities. The absence of differences in functional capacity and lower extremity function suggests that daily activities are not yet impaired in asymptomatic children. Future studies including broader age ranges and children with higher Beighton scores, employing advanced methods and long-term follow-up, are warranted. Keywords: Functional capacity, Functionality, Hypermobility, Muscle strength, Postural balance, Rotational profile