Knee flexion while walking versus knee contractures in children with bilateral spastic cerebral palsy

Flexed knee is a multidimensional kinematic walking pattern in children with bilateral spastic CP that has been described to develop as gait matures, particularly at higher GMFCS levels (1). One cause might be limited knee extension that have been described to lead to significant disability with a flexed knee gait posture during walking (2). The aim of this study was to compare knee position during walking with passive knee extension in an unloaded body position, and with respect to functional mobility during walking. Gait in 30 children with bilateral spastic CP (13 females) median [min, max] age 11.3 [7.6, 17.1] years and 22 typical developing (TD) children (11 females) median [min-max] age 8.9 [6.5-16.9], was assessed with 3D-motion analysis (Vicon MX40®). Joint contractures in ankle, knee and hip, defined from a neutral joint position, were assessed through goniometric measurement of passive hip extension, knee extension, and ankle dorsiflexion with extended knee in supine position. Orthopaedic lower limb surgeries were documented. Functional mobility was measured with the time up and go test (TUG). Non-parametric statistics were used (p<0.05). Knee contractures were greater at GMFCS III than at GMFCS I and in the TD group (p=0.046 and p= 0.002). During walking, knee angle at initial contact (KneeAngleIC) was greater than peak knee extension in stance (MinKneeFlexSt) in the TD group and at GMFCS I, II, and III (p=0.008, p=0.043, 0.005, and p=0.002) respectively. MinKneeFlexSt exceeded maximum passive knee extension at GMFCS levels II (p=0.004), and III (p=0.002). Both KneeAngleIC and MinKneeFlexSt were greater at GMFCS II and III, than at GMFCS I and the TD group (Fig. 1). TUG took longer for GMFCS II and GMFCS III compared to TD (p<.001 and p<.001) and GMFCS I (p= 0.001 and p<0.001), and longer for GMFCS III compared to GMFCS II (p<0.001). Fig. 1 Light bars represent KneeAngleIC and dark bars MinKneeFlexSt. (+) indicates knee flexion, brackets above the boxes: differences at KneeAngleIC, and below: differences at MinKneeFlexSt.Download : Download high-res image (58KB)Download : Download full-size image This study found that knee flexion in stance was significantly greater than knee contractures at GMFCS levels II and III with no difference in occurrence of orthopaedic surgery. Furthermore, walking ability took longer at GMFCS level III compared to at level II at similar knee flexion contracture. The discrepancy in knee position in weight-bearing versus passive knee extension in the unloaded position at GMFCS II and III, and the large difference in TUG between children at GMFCS level III and those in the other groups, are likely explained by the effort to overcome motor disorders such as spasticity, however, may also be explained by the commonly occurring sensorimotor disorders (4).