In order to perform normal, pain-free shoulder motion, it is necessary that there is adequate strength around the joint. While this sounds simple, normal shoulder motion depends on what are called “force couples” – opposing forces that act simultaneously on the shoulder during motion to provide stability. If these force couples are disrupted, abnormal motion of the shoulder can occur and can contribute to shoulder pain and instability.
Shoulder Elevation, Stability & Force Couples
Force couples play a significant role when raising the arm overhead. For example, as the deltoid muscle contracts to elevate the arm, the muscles of the rotator cuff exert a downward force on the humerus which works to maintain proper alignment of the ball-and-socket components of the shoulder joint.
In addition to this, the trapezius and serratus anterior muscles must function simultaneously to perform elevation. As the different parts of the large trapezius muscle contract, the shoulder blade rotates and is assisted and stabilized by a co-contraction of the serratus anterior. This ensures that there is adequate rotation of the shoulder blade and minimal excess motion occurring with active overhead reaching.
Lastly, the muscles of the rotator cuff provide additional stability at the shoulder by applying forces on the anterior (front) and posterior (back) aspects of the joint. The external rotators – teres minor & infraspinatus – apply a force from the posterior aspect of the joint. While the subscapularis, which performs internal rotation, applies a force to the anterior aspect of the joint. These work together to center the humeral head in the joint which promotes stability at the shoulder.
Weakness and Pain in the Shoulder
If these force couples are disrupted, abnormal motion can occur. This can happen when weakness develops in any of these muscles and leads to decreased congruity of the bony structures that make up the joint. This allows for excess motion that can impinge on nearby structures which can lead to inflammation and pain in the shoulder during overhead motion. Over time, these faulty movement patterns can damage the tissues in the shoulder joint and limit one’s ability to participate in recreational activities or complete daily activities around the house.
If you suffer from shoulder pain, physical therapy can provide relief. Call Respire Physical Therapy today at 703-671-1871 or click here to schedule an evaluation with a Physical Therapist today to get on the path to pain-free movement!
Tags: shoulder instability, Shoulder weakness, physical therapist, choosept, arlingtonva, alexandriava, Physical Therapy, fallschurchva, Respire Physical Therapy, ptworks, Shoulder Injury, health blog, Shoulder Pain
