Pain is stimulated mainly by the stretching of smooth muscle or organ capsules .Severe acute abdominal pain can be due to a large number of gastrointestinal conditions ,and normally presents as an emergency.An acute abdomen can occasionally be due to referred pain from the chest ,as in pneumonia ,or to metabolic causes ,such as diabetic ketoacidosis .

The effects of drugs against pain are different for different people. In addition, pain tolerance varies greatly from person to person. For this reason, a drug is not suitable for everyone with the same injury. For example, some people are very satisfied with the medications prescribed by a sprained ankle, while others need a prescription pain reliever stronger. Drugs with proper pain depends on the person experiencing the pain, not in the condition that causes pain.

A painful ,stiff shoulder can result from rotator cuff lesions and is also seen following hemiplegia ,chest or breast surgery or myocardial infarction.Painful shoulders may also be the initial presentation of Rhematoid arthritis ,less commonly a seronegative spondarthritis ,and of polymyalgia rheumatica in the elderly.