When assessing muscle pathology try to decide which one of the four basic patterns of abnormality is present:
Muscle edema, i.e. increased signal intensity on T2-weighted images in muscle with otherwise normal anatomic architecture:
Injury
Myositis: infectious myositis, necrotising fasciitis, auto-immune myositis (polymyositis, dermatomyositis)
Imflammatory myopathy: Graves disease
Radiation therapy
Muscle atrophy, i.e. too much fat:
Disuse
Chronic denervation due to nerve entrapment, poliomyelitis
Muscular dystrophy: Duchenne
Mass within muscle:
Soft tissue tumor
Hematoma
Abscess
Accessory muscle, i.e. abnormal anatomy with normal signal