The objective and dynamic documentation of the knee kinematics in ambulatory children with spastic cerebral palsy and the examination of possible causes of differences when compared to normals.

17 ambulatory patients with an average age of 10,5 years (6–17 years) with cerebral palsy, spastic diplegia where examined clinically including Duncan-Ely test. They were also examined with 3-D instrumented gait analysis. The Elite system with six cameras was used and the knee kinematics in the sagittal plane was recorded.

Almost all patients (16/17) had a positive Duncan-Ely test during clinical examination. The knee kinematics in the sagittal plane showed that in 20/34 knees the range of motion was decreased compared to normal values. In 30/34 knees there was a delayed maximum knee flexion in swing phase and in 16/34 knees the amplitude of the maximum knee flexion was decreased compared to normals. Patients with severe crouch or mild rectus spasticity had almost normal knee flexion.

Foot clearance in swing phase is one of the basic prerequisites of normal gait. Patients with spastic cerebral palsy who are able to walk have an impaired foot clearance because of the pathological action of the rectus femoris.

In our study the majority of the patients with clinically confirmed rectus spasticity had decreased timing and amplitude of max. knee flexion in swing. In patients with severe co-contraction of the knee flexors and extensors max. knee flexion within normal range. Therefore it should not be considered as the only evaluation parameter in rectus femoris spasticity.

We treated 20 children (40 limbs) with diplegic cerebral palsy who could walk by multilevel soft tissue operative procedures including conversion of the biarticular semitendinosus and gastrocnemius to monoarticular muscles. The mean age at surgery was 11.5 years (5.6 to 17.0). All patients underwent clinical and radiological examination and three-dimensional instrumented gait analysis before and at a mean of 3.1 years (2.0 to 4.5) after surgery.

The passive range of movement at the ankle, knee and hip showed improvement at follow-up. Kinematic parameters indicated a reduced pelvic range of movement and improvement of extension of the knee in single stance after operation (p < 0.0001). However, postoperative back-kneeing was detected in five of the 40 limbs. The kinetic studies showed that the power of the hamstrings and plantar flexors of the ankle was maintained while the maximum knee extensor moment during stance was reduced. The elimination of knee flexor activity of semitendinosus and gastrocnemius combined with transfer of distal rectus femoris led to an improvement in gait as confirmed by gait analysis.