Introduction: Isolated shortening of m. gastrocnemius (ISG) restricts dorsal flexion of the ankle resulting in compensatory mechanisms during gait which can lead to pain and deformity due to excessive pressure and foot overload. Clinically, ISG is defined as the difference between dorsal flexion of the ankle with the knee in extension and flexion. There is no clear consensus on the definition of an ISG value in the literature, but most authors suggest a difference of 10° – 13°. The prevalence of ISG is thought to be high in a healthy population, even higher in patients with forefoot pathology and still unknown in patients with knee and/or hip pathology. Purpose: To determine the prevalence and value of ISG in patients with knee and hip pathology before elective surgery (arthroscopy of knee/hip and arthroplasty of knee/hip), and to find possible correlations between ISG and the following variables: patients demographic data, range of motion and pain. Methods: 80 patients who were admitted to the Orthopedic clinic of the University Medical Center of Ljubljana for elective surgery on the knee or hip joint were classified into 4 groups according to pathology and age. We measured ISG with a weight-bearing lunge test with knee in extension and flexion using a fluid goniometer. Patients also filled out a questionnaire. Results: Patients in hip arthrosis group had a statistically significant increase in the ISG at ISG ⡥ 10 ° than patients in the hip labrum injury group. There were no statistically significant differences when comparing the presence of ISG between patients with menisci injury of the knee and hip labrum injury, and patients with knee arthrosis and menisci injury of the knee. The prevalence of ISG ⡥ 10° in subjects with hip pathology was 47,5 % and the prevalence of ISG ⡥ 13° was 21,2 %. In subjects with knee pathology, the prevalence of ISG ⡥ 10° was 26,2 % and the prevalence of ISG ⡥ 13° was 7,5 %. The mean difference between dorsal flexion of the ankle with the knee in extension and flexion of all subjects was 7,79° ± 3,96° and was statistically positively correlated with age and pain and negatively correlated with physical activity. Discussion and conclusion: ISG is to some extent present in different patient populations. Further research using a standardized protocol needs to be done for the diagnosis of ISG, which would allow for incidences and impact of different pathologies to be determined.