The big goals of stroke rehab are to enhance muscle control and reduce spasticity which refers to constant contraction of muscles that can lead to pain and other problems.
The shoulder is a key problem area after a stroke. The shoulder blade (scapula) and the upper arm bone (humerus) come together to form the shoulder joint. This joint is shaped like a ball and socket. Problems with the shoulder muscles can cause this joint to partly dislocate due to the weight of your arm. This partial separation (subluxation) makes your shoulder droop down.
Subluxation can cause pain with movement and a sensation that your shoulder is out of joint. Muscles, tendons, and ligaments can become overstretched. These muscle problems can lead to other problems with your shoulder as well, such as reduced range of motion. Some of the muscles may also be permanently shortened. This is called contracture.