Your muscles help you move and help your body work. Different types of muscles have different jobs. There are many problems that can affect muscles. Muscle disorders can cause weakness, pain or even paralysis.
Causes of muscle disorders include
Injury or overuse, such as sprains or strains, cramps or tendinitis
A genetic disorder, such as muscular dystrophy
Some cancers
Inflammation, such as myositis
Diseases of nerves that affect muscles
Infections
Certain medicines
Sometimes the cause of muscle disorders is unknown.