There are several reasons that you may have difficulty reaching overhead or behind your back.
Each joint in your body has a joint capsule, which is a tough membrane that surrounds each joint and contains fluid to allow smooth movement.
The capsule can tighten over time if you don’t move your arm into certain positions.
For example when your arm is in a sling for a few weeks your shoulder joint capsule will limit your ability to move your arm overhead, which is different than limitations due to tight or weak muscles.
A physical therapist using mobilization techniques using a strap to stretch the joint capsule and return normal range of motion to your shoulder
