Arthritis that affects your “shock absorbers” is the cause of pain and disability in knee and hip joints that can lead to surgery. Click here. Learn the symptoms, causes, and treatments of piriformis syndrome. The causes of back pain can be complex -- accidents, muscle strains, sports injuries.Stiffness, pain, lower back pain, and pain radiating down the leg are symptoms of back pain.se your muscles incorrectly, too much, too little -- and you’ve got muscle pain. Learn the subtle differences of muscle injuries and pain. Overuse injuries -- muscle sprains, strains, and pains -- result from all sorts of assaults, small to severe.