Cerebral palsy (CP) is a motor impairment due to a brain malformation or a brain lesion before the age of two. Spasticity, hypertonus in flexor muscles, dyscoordination and an impaired sensorimotor control are cardinal symptoms. The brain lesion is non-progressive, but the flexor muscles of the limbs will during adolescence become relatively shorter and shorter (contracted), forcing the joints into a progressively flexed position. This will worsen the positions of already paretic and malfunctioning arms and legs. Due to bending forces across the joints, bony malformations will occur, worsening the function even further. Currently, the initial treatment of choice is the use of braces, which diminishes the shortening somewhat, but eventually lengthenings of tendons and release of aponeuroses around the muscles often is needed, and transfers of wrist flexors to wrist extensors may improve wrist position. But the long-term results are unpredictable- how much does the muscle need to be lengthened? What muscles should be transferred for a better position of the wrist, and at what tension? A method to measure sarcomere length in vivo has been developed. The sarcomere, the distance between two striations, is the smallest contractile unit in the striated muscle. When, during surgery, a muscle fiber bundle is transilluminated with a low energy laser light, a diffraction pattern is formed. This diffraction pattern reflects the sarcomere length, and thereby an instant measure of how the stretch of the muscle is obtained. When performing tendon transfers of e.g. wrist flexors to wrist extensors, the setting of the tension of the transfer is arbitrary, and the long-term result is unpredictable. Laser diffraction measurements will give a guide to a precise setting of tension. It is known that there may be pathological changes in muscle in cerebral palsy that also will affect the long-term results of tendon lengthenings and transfers. In order to also take these changes into account, small muscle biopsies will be taken during the same surgeries. These will be examined with immuno-histochemical and biochemical techniques, gel-electrophoresis as well as electron microscopy.