Knee flexion deformities and genu recurvatum in cerebral palsy: roentgenographic findings.

Patients with cerebral palsy often have recurvatum or flexion deformities at the knee. To determine whether these are due to a bony or soft-tissue abnormality, four angles were measured on lateral roentgenograms of the knee: the femur-physis angle (angle 1); femur-Blumensaat's line angle (angle 2); tibia-plateau angle (angle 3); and tibia-physis angle (angle 4). These angles were measured for 45 patients with knee flexion deformities and for 31 with genu recurvatum. Values were also obtained from 204 normal lateral knee reoentgenograms. The age range for the whole series was from one to 22 years. Angles 2, 3 and 4 decreased from normal values with increasing age. The angulation of the proximal tibia, as measured by angle 3, is abnormal in patients with flexion deformities. Angles 2 and 3 were abnormal in cerebral-palsied patients with flexion deformities, while patients with genu recurvatum showed no significant bony abnormalities. These results suggest that treatment of flexion and recurvatum should be based on etiology.