Armpit pain can have many causes, ranging from injuries and irritants to infections that cause swollen lymph nodes. Less commonly, the pain—referred to as axillary pain—may be due to an autoimmune or arterial disease, nerve compression, and malignancies like breast cancer.
An injury or arthritis most likely causes pain outside the knee. A doctor can determine the cause based on your other symptoms and the results of imaging tests.
Intercostal muscle strain is an injury affecting the muscles between two or more ribs. Symptoms can include sharp, direct pain, stiffness, and mobility difficulties.
A scapula fracture is an uncommon injury. The scapula, or shoulder blade, is a wide, flat bone that sits behind the rib cage. The scapula connects to the clavicle (collar bone) in the front of the body, and to the humerus (arm bone) at the side.
Chondromalacia patella, also known as runner's knee, is a knee condition that can cause pain and grinding when the knee is flexed. It's due to the breakdown in the cartilage on the undersurface of the kneecap (patella) that causes bones to rub against each other.
