(en) In patients with haemophilia, the long-term consequences of repeated haemarthrosis include joint cartilage damage and irreversible chronic arthropathy, resulting in severe impairments in locomotion. Quantifying the extent of joint damage is therefore of paramount importance in order to prevent disease progression and compare the efficacy of treatment strategies, such as prophylaxis. Musculoskeletal impairments in patients with haemophilia may stem from structural and functional abnormalities, which have traditionally been evaluated radiologically or clinically. However, clinical and radiological scores generally underestimate the degree of joint pathology in the early stages of arthropathy. In addition, they are insensitive to detect subtle changes in long term follow-up and unable to discriminate between different stages of arthropathy. The aim of this thesis is to propose three-dimensional gait analysis as an innovative approach designed to focus exclusively on the functional component of the joint. Moreover, contrary to radiological and clinical examinations that usually assess the patient in supine position, i.e., in a non-weight-bearing situation, gait analysis allows us to objectively quantify joint motion, muscle moment, and power under dynamic and weight-bearing conditions. This is of the utmost importance, as pain induced by weight-bearing activities most likely has a significant influence on the functional performance of the arthropathic joints. This thesis aims to increase our knowledge about the biomechanical consequences of haemophilic arthropathy on gait pattern in patients with haemophilia. In order to determine the scientific credibility of gait analysis, the reproducibility and sensitivity to change of this tool were first tested. Thereafter, the impact of lower limb impairments on gait was studied in order to better understand the physiopathology of gait in patients with haemophilia. An overall elevation of the vertical displacement of the body’s centre of mass was observed in patients with haemophilia with multiple joint impairments. This should have normally resulted in increased mechanical energy being produced as more mechanical energy was needed to redirect the centre of mass vertically. However, mechanical work was found to decrease slightly, which may be explained by a energy-saving strategy of patients with haemophilia to conserve part of the muscle mechanical work and save mechanical energy via an efficient pendulum mechanism of gait. Finally, gait analysis was tested as an assessment tool in the context of a clinical study. We experimentally investigated the effects of custom-made orthopedic insoles and shoes in patients with haemophilia with ankle arthropathy. Our study suggested that orthoses may have beneficial effects, as they provide significant pain relief and comfort improvement, with minimal side effects.