Shoulder Instability and Dislocations

The shoulder is a joint designed for mobility, with more degrees of freedom than any other joint in the body. But excessive mobility can lead to shoulder instability, subluxation, or dislocation, with peak incidences of injury occurring in athletes in their 20s. Our clinic sees patients of all ages seeking physical therapy for shoulder pain or a feeling that they’re “unstable” due to either previous dislocations or a history of chronic stress to the area (a Chicago summer filled with diving catches and beach volleyball, perhaps?)
The primary cause of shoulder dislocation is trauma, from either collision with an object (or player), falling on an outstretched arm, or having the arm quite literally “pulled out of socket.” During these accidents the soft tissues that hold the shoulder together — ligaments, tendons and muscles — get stretched out forcefully, and afterwards the shoulder joint can stay overly lax. It’s estimated that 70% of people that dislocate their shoulder can expect to re-dislocate within 2 years, and that rate is even higher in high school and college age injuries. (Why? Probably due to the fact that younger people have “stretchier” collagen, which creates a less stable joint after being overstretched.)
The most common way to dislocate a shoulder is when your arm is shoved into an abducted and externally rotated position, like when a quarterback about to throw gets sacked, or a basketball player attempts to block a hard pass. The top of the arm bone (the ball or head of the humerus) slips forward out of the socket to some degree. This can lead to labral tears (a tear of the thick cartilage ring that deepens the socket), deformation or tearing of the stabilizing ligaments, and excessive stretching or tearing of the rotator cuff and biceps muscle and tendons. Occasionally the arm bone slams into the socket so hard that it causes a small compression fracture on the back of the bone.
In many cases, dislocated shoulders do not require surgery (particularly in older patients), but due to all that stretching, they do require rehab. If the ligaments are stretched or torn, it is even more important to keep the rotator cuff strong and to keep the shoulder socket in the right place by keeping the shoulder muscles strong. When the scapular stabilizers are weak, the shoulder blade may “wing” off the back, putting the socket too far forward and increasing the strain on already weakened ligaments. And in extreme positions like seen in overhead athletes (think also of a baseball pitcher, or a tennis serve — or even a freestyle swim stroke), the rotator cuff and biceps help to hug the arm bone snugly in the socket.
Recurrent dislocation is bad — first off, it hurts A LOT when your arm slips out of socket. Secondly, you’re at continual risk of tearing those structures or even damaging the nerves around the arm. Also important for athletes is the fact that unstable joints have poor proprioception and a tendency to move inefficiently, which leads to an inability to perform at maximal potential. Strengthening the rotator cuff and improving neuromuscular control — making your shoulder smarter — will help prevent instability and improve performance. See your physical therapist as soon as possible to get started on the right track after injury.
To help prevent instability/dislocation and to help stabilize an already unstable shoulder, work on strengthening the scapular stabilizers, the rotator cuff and deltoids, and work on making the shoulder smarter with neuromuscular and proprioceptive drills.
Three rotator cuff/stability exercises to get you started:
ER/IR with TB
SL horizontal abduction
Cheerleaders
Reference: Hayes K, Callanan M, Walton J, Paxinos A, Murrell G. Shoulder Instability: Management and Rehabilitation. J Orthop Sports Phys Ther. 2002;32(10):497-509. doi:10.2519/jospt.2002.32.10.497.,