Hip osteoarthritis (OA) is a chronic and often progressive musculoskeletal condition with no known cure. Hip OA affects the whole joint organ and patients with advanced stages of the disease experience pain, stiffness and dysfunction. Conservative management of hip OA consists of reducing symptoms and improving function, while total hip replacement (THR) is often the end stage outcome. Walking is an integral activity of daily living and commonly prescribed as an exercise in people with hip OA. Studies to-date have focused on understanding how advanced stage hip OA impacts on gait and physical function, with limited studies in people with mild-to-moderate hip OA. The general purpose of this thesis was therefore to investigate the influence of mild-to- moderate hip OA on gait and physical function at baseline and to identify if gait adaptations occur over time. The thesis consisted of a systematic review and 3 experimental studies. Physical function and patient reported outcomes were initially assessed in individuals with mild-to-moderate hip OA (n = 27) and healthy age-matched controls (n = 26). Individuals with hip OA demonstrated poorer function with 13% slower self-selected walking speed, 38% slower timed-up-and-go (TUG) test and 36% slower timed stair test (TST) times, 20-48% weaker lower limb muscle strength and 18-47% less hip range of motion. There was no difference in physical activity between the two groups. Hip flexor and knee extensor muscle strength were the most consistent uni-variate predictors of overall Hip Disability and Osteoarthritis Outcome Score (HOOS) and its corresponding sub-scores, whereas TST was the best predictor of the modified Harris Hip Score (HHS) and its corresponding function score.