It is very important to exercise the shoulder after even minor shoulder injuries because even small injuries can develop into a frozen shoulder. This is known as secondary stiffness. Basically, after any sort of trauma the shoulder will tend to stiffen up and that’s when it is particularly vulnerable to freezing.
Exercises to avoid frozen shoulder should include both shoulders, even if only one shoulder is injured. This is so that the working elements of the painful shoulder becomes as strong as the pain-free one. If, however, you are experiencing pain in BOTH shoulders, the exercise regime should be undertaken every other day.