The shoulder is a very complex joint. There are many muscles and ligaments that surround the shoulder joint to both keep it stable, and to allow you to move your arm in all of the directions that you are able to. These muscles and ligaments eable you to be able to do everything from washing your hair, to reaching high up in a cupboard, scratch your back, throw a baseball or football, get your wallet out of your back pocket, and put your shirt on (among many other things). This ability to move your shoulder in so many different directions means that the shoulder has to be pretty flexible. This amount of flexibility is usually a very good thing, but it can also cause some problems. As certain muscles around the shoulder start to lose flexibility or strength, it can place increased stress on other muscles and ligaments in the shoulder. This increased stress can cause irritation and inflammation, resulting in pain. A Physical Therapist's job is to identify the areas of weakness and abnormal movements, and to determine a treatment plan to rehabilitate these areas.