Acromio-clavicular joint osteoarthritis

Most ACJ arthritis is caused simply by wear and tear of the joint over several decades. Hence the risk of developing osteoarthritis in the shoulder, as well as physical limitations and pain, increases as you grow older.  Typically people with manual jobs or labouring jobs are at risk, as are weight-lifters and sports people (tennis, rugby, boxing are all common).

An injury to the shoulder can end up leading to arthritis later on, regardless of how old you are.  This is attributed to swelling, pain and even the development of bone spurs, whenever the two bones are rubbing together. Most of the time, the condition occurs in those who are over the age of 50. 

In younger individuals, the condition can result from trauma or injury, such as a sprained or a fractured ACJ, which is known as posttraumatic arthritis.  The condition can also be hereditary.