Patient stated that the pain wakes him up at night. It is worse during the day than when he wakes up in the morning. The pain was described as local, achy but can be sharp and intermittent. He could not relate it to any physical activity. There is no history of trauma but when he is in pain, it is difficult to raise his arm overhead from the pain. The patient stated that the pain began a few months ago and has been gradually getting worse gradually since. There is no numbness or tingling in his left upper extremity. He has no neck pain. This patient is not on any medication and does not smoke. This patient is a K-8 art teacher. He is 20 pounds overweight and although he is on his feet all day, he does not follow any regular workout routine. This patient has no heart conditions or diabetes.

Question: Based on this patient’s clinical history, what are some differential diagnoses you are considering?