In the explanation of musculoskeletal disorders, the skeleton is usually put forward, and the muscles tend to be forgotten. This seems to be a mistake, and leads to some common misunderstandings, like osteoarthritis being the cause of joint pain, rheumatoid arthritis being an auto-immune disease, disc herniation as the cause of low back pain, meniscal injury as the cause of knee pain, etc. This in turn will lead to inappropriate treatments like painkillers - which sometimes kill the patient, and anyway never treat the root of the pain - or to avoidable surgery. Misunderstanding the role of muscle contractures in other ailments like scoliosis or migraine has not allowed so far a disease-modifying treatment. All the above-mentioned disorders can however be cured, in most cases, by manually treating the causal muscle contractures, which is rather simple. This book explains the origin, the mechanism and the consequences of muscle contractures, as well as the pathomechanisms of joint pains, scoliosis, migraine, and several other diseases, and the principles of their treatment. We will present several research studies showing the efficiency of a simple manual treatment of the contractured muscles that are the prime movers of these diseases.