Functional rehabilitation of the cruciate-deficient knee.

'Functional rehabilitation' is an embellishment of the traditional concepts of rehabilitation which are motion and strength. Functional rehabilitation incorporates the concepts of agility, proprioception, and finally the confidence of the individual when performing whatever task he or she wishes to undertake. The determinants of rehabilitation include the patient, the type of injury the knee has sustained as well as its surgical treatment, and how innovative the director of rehabilitation is. The principles of rehabilitation include joint motion and stability as well as muscular endurance and strength. These should be considered during the immobilisation phase, the surgical and postsurgical phase, and continued through the early healing, late healing and final healing stages. The rehabilitation director must advance activity to levels of ever increasing complexity. Various modalities of rehabilitation such as bracing, passive motion machines and muscle stimulation units should be added in an effort to achieve a painless course. This course is progressive as long as errors of rehabilitation are avoided, including overtraining and too rapid a progression resulting in injury or reinjury. Realistic goals must be firmly established in the mind of the patient and the director at the outset. Determinants of rehabilitation are a guide to the reality of reaching a functional level. The functional activity programme depends upon knee stability, successful completion of lesser activities and healing of the injury or the surgery. Progressing from less difficult to more difficult activities before the patient is ready usually results in an injury or reinjury. Therefore, constant assessment of the performance level of the patient must be made before advancing to more demanding activities. Conservative and surgical treatment programmes for functional rehabilitation are essentially the same except for the time factors involved. The times of completion of different levels of activity are generally longer in the surgical programme. Time alone is not the signal for advancement from one programme to another. Attention should be paid to range of motion, strength, fluidity of performance of functional activities as well as functional testing.