The mechanics of activated semitendinosus are not representative of the pathological knee joint condition of children with cerebral palsy.
Measurement of the popliteal angle is used to assess hamstring contracture in children with cerebral palsy. The popliteal angle in 482 normal children, 1-10 years of age, was measured. Using a 360 degrees goniometer, the popliteal angle was measured with the hip held at 90 degrees flexion to indicate hamstring muscle tightness. Between the ages of 1 and 3 years, the mean angle was 6 degrees (range, 0-15). At age 4, the angle rose to 17 degrees in girls and 27 degrees in boys (range, 5-45). At greater than or equal to 5 years the mean angle was 26 degrees with little change (range, 0-50). A popliteal angle of greater than 50 degrees in the above age groups indicates abnormal hamstring tightness.