Rotator cuff tendinitis, an injury, a heart attack, a broken shoulder bone and certain diseases can cause shoulder pain, according to Healthline. An overuse injury, a sports injury, nerve entrapment, a bone fracture and irritation of the underarm may bring about armpit pain, notes Healthgrades.
Arthritis, rheumatoid arthritis, osteoarthritis and septic arthritis are diseases that can lead to shoulder pain, notes Healthline. Overuse injuries to nearby areas; bone spurs; frozen shoulder, which is the stiffening of muscles, tendons or ligaments; torn cartilage and a torn rotator cuff can result in shoulder pain.
Other causes of shoulder pain include pinched nerves, broken arm and shoulder separation, which is the tearing of the ligaments that connect the collarbone to the shoulder plate, explains Healthline. Home remedies for shoulder pain include using over-the-counter pain medications, resting the shoulder for several days and compressing the affected area with an elastic bandage to relieve swelling.
Fibromyalgia, the common cold, surgery, cysts and viral infections may result in armpit pain, explains Healthgrades. Life-threatening causes of armpit pain include angina, which is chest pain due to a low supply of blood to the heart, severe fracture; tumors and deep vein thrombosis of the arm. The latter condition is dangerous, because it is a blood clot that can get free and cause a heart attack, stroke or pulmonary embolism.