You’ve Heard Of Tennis Elbow, But What About Tennis Shoulder?
What is Posterior Shoulder Instability (psi)?
PSI happens because of lot of reasons including anatomical features, loss of strength, loss of motor control, and prior shoulder trauma. Repetitive movements including overhead, reaching across the body, and internal rotation contribute to microtrauma in the back of the shoulder. These shoulder movements stress the posterior labrum, capsule, and rotator cuff. This resulting microtrauma can lead to translation of the humerus in a posterior direction in the glenohumeral joint. This posterior translation may contribute to various injuries within the shoulder joint.
The shoulder is a complex structure relying on mostly muscles for active stability. The shoulder joint itself mimics a softball on a golf tee as the head of the humerus is massive in comparison to the surface of the shoulder blade on which it sits. When muscles are weak or inactive, this dynamic group of structures breaks down.
Left Photo: Side view of the shoulder complex with the 2 posterior rotator cuff muscles shown
Right Photo: Front view of shoulder complex showing the inside of the shoulder joint where the humerus will translate toward the back in PSI
Tennis, baseball, and all throwing sports
A recent articles, “Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management” published in the International Journal of Sports Physical Therapy provides an overview of the effects of PSI on tennis players.(1) High reps at high forces of tennis movements including the forehand follow-through, the initial phase of the backhand, backhand volleys, and kick serves put the shoulder at risk for developing PSI.
Athletes of all throwing sports are susceptible to PSI due to the forces on the posterior shoulder joint during the deceleration phase (or follow-through) of a throw.(2) In baseball, PSI is known as “batter’s shoulder” as baseball players experience intense deceleration phases during throwing and batting.(3) As the shoulder moves across the body while internally rotating, the capsule on the back of the shoulder is being stretched. The muscles (shown in the Left Photo above) in the back of the shoulder joint are actively working at high forces to slow down the movement and control the end phase of the swing/throw. This results in break down over time.
My shoulder is “loose”, do i have PSI?
Lets examine the difference between loose shoulders (hyperlaxity) vs instability.
Hyperlaxity - increase in controlled joint translation due to elongation of soft tissue structures (muscles, ligaments, etc) - NOT painful
Instability - increase in joint translation that is NOT controlled - PAINFUL
If you have excessive movement in your shoulder joint but no pain, your body may be functioning well and controlling this hyperlaxity; however, if your excessive movement is painful, you may be experiencing some type of instability, possibly PSI.
Next week - PArt II
Next week the SciSport blog will continue the discussion of PSI with Part II. Clinical presentation, diagnosis, and return to play treatment of PSI from the article “Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management” will be discussed next week!
Struggling with shoulder pain or weakness? Play an overhead, racquet, or throwing sport? Book a session with our sports physical therapist or sports performance coach today!
If you’ve had an injury and are in need of a return to play program, schedule a physical therapy session with us to get back to your sport. Get back in the game ready to meet your sport specific demands.
References:
Watson L, Hoy G, Wood T, et al. Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management. IJSPT. 2023;V18(3):769-788.
Schubert MF, Duralde XA. Posterior shoulder instability in the throwing athlete. Oper Tech Sports Med. 2021;29(1):150802.
Philips B, Andrews J, Fleisig G. Batter’s Shoulder: Posterior Instability of the Lead Shoulder, A Biomechanical Evaluation. Alabama Sports Medicine and Orthopaedic Center; 2000.
Disclaimer: This SciSport blog post is a summary of an article printed in an academic research journal. The purpose of this blog post is to provide readers with academic and educational content in an easy-to-understand format. We take no credit for the material and knowledge presented, and we encourage readers to take a look at the original source provided in the References section
