A total of 123 patients with Duchenne muscular dystrophy (DMD) was surgically treated during two different periods of their course by hip and knee release, aponeurectomy of the iliotibial band and z-shaped Achilles' tendon lengthening. In 57 patients (group I) this was carried out prophylactically as retractions of the lower limb joints were just beginning at the age of 6.4 +/- 1.43 years and in 66 patients (group II) as mild contractures of the joints at the end of walking ability were already manifest with an average age of 9.27 +/- 1.86 years. The average follow-up was 3.7 +/- 1.2 years in both groups. To be able to assess the interindividual course of both groups, we defined "joint and motor quotients", which allowed a complex assessment of joint function and motoric capacity. In addition, both groups were compared with a control group (natural history) consisting of 100 non-operated DMD patients. In both groups a significant release of the contractures could be obtained primarily. Patients in group I showed a much better long-term effect than those in group II. The motor quotient in group I was significantly better over the whole follow-up period (P < 0.001) than in group II or the control group. The prolongation of walking ability by about 2 years compared with the natural history is in our opinion not the central goal of this surgical treatment concept of lower limbs in DMD, but rather the additionally achieved prolongation of an assisted standing ability with the lower limbs free from contractures and deformities.(ABSTRACT TRUNCATED AT 250 WORDS)