The initial assessment is the basis for any therapeutic program in musculoskeletal rehabilitation, whatever the treatment approach used, and is necessary for planning a treatment personalized to the individual patient. It is particularly important in patients with non-specific and multifactorial disorders. The biopsychosocial model highlights the role of non-biomechanical factors that can influence the genesis and the prognosis of patients with musculoskeletal pain. This article describes the role of sleep quality in pain and in musculoskeletal rehabilitation.