If you have shoulder pain, you’ve probably wondered what exactly is causing you to have this pain that is interfering with your everyday life. You may have even wandered the Internet attempting to self diagnose in the hopes that you can treat on your own. During your search you come across many, many potential causes. Conditions like tendinitis, arthritis, rotator cuff tear, frozen shoulder, instability and dislocation will come up during your search. Another term you will find is shoulder impingement, which if not treated can eventually lead to rotator cuff tendinitis and tears. What is shoulder impingement?
If you have pain with overhead activities, pain at a certain point or range while lifting your arm over your head, pain with quick pushing or pulling movements, an inability to sleep on your shoulder, and a history of repetitive use of your arm, your shoulder pain may be due to shoulder impingement. The shoulder joint is composed of the arm bone (humerus), which articulates with a surface (glenoid) from the shoulder blade (scapula) forming the gleno-humeral joint. The space above the humerus (supra-humeral or sub-acromial space) is housed by another piece of bone from the shoulder blade, the acromion. Within this space, which is about 10mm big, there exists four structures. These structures are the long head of the biceps tendon, the shoulder’s joint capsule, a bursa, and the supraspinatus muscle and tendon. When the shoulder is functioning properly, these structures occupy this space without any interference. When functioning improperly, this space is narrowed and these structures are ‘pinched’ or ‘impinged’ causing shoulder pain, weakness, and loss of motion.
What causes these structures to become impinged upon? If you have primary impingement, this space becomes progressively occupied by bone spur formation on the undersurface of the acromion. These bone spurs form from either an anatomical variation in which the acromion ‘hooks’ into the subacromial space or through degeneration in which repetitive use causes microtrauma to the undersurface of the acromion and the body responds by forming bone. This form of impingement typically occurs in older adults or people with anatomical differences in their acromion, and is corrected surgically. Secondary impingement is more common and typically occurs in younger people aged 25-40. The reason the structures in the subacromial space are pinched is not due to bone occupying the already narrow space, but due to instability where the humerus cannot be held correctly in place and the humerus migrates up into the space causing impingement.
Secondary impingement, where the humerus is not held correctly in the joint, can occur for a few reasons. The rotator cuff composed of four small muscles that attach from your shoulder blade to your humerus function to hold the humerus in place. When these muscles are overworked, say from repetitive overhead activity, or are weak, they cannot hold the humerus in place and impingement occurs. In addition, when your shoulder blade is not positioned properly, the rotator cuff muscles are placed in sub-optimal conditions causing them to overwork and fatigue eventually leading to impingement. Like all synovial joints (joints that allow motion to occur), the shoulder joint is surrounded by a capsule, which houses the fluid that lubricates and nourishes the joint. If the back of the capsule is too tight, it can push the humerus up and forward into the subacromial space. Another cause of secondary impingement, that is applicable to virtually everyone, is posture. If you have a slouched posture where your head is forward, shoulders are rounded and mid back is flexed, the shoulder blades and rotator cuff muscles are put out of place and shoulder motion is lost. You can see this work if you try it yourself. Sit in a slouched posture and try to lift your arm overhead, now sit up straight and try lifting your arm once again. You can see how posture affects the way that your shoulder moves just by attempting this at home. Poor posture also causes the front portion of your body to become tight and the back muscles to become stretched out and weak.
As impingement occurs, whether primary or secondary, if it is not addressed it can lead to bigger problems down the road. As the structures in the subacromial space are repeatedly impinged, irritation and pain occur leading to edema (swelling or buildup of fluid) and inflammation of the structures and the joint. The edema and inflammation along with continued shoulder impingement then progresses to tendinitis and degeneration of the structures. With inflammation and degeneration, which is also seen in primary impingement, along with further shoulder impingement leads to bone spur formation, and even rotator cuff tears. You can see how this nagging shoulder pain, if not addressed, can really snowball out of control.
Now that you understand a little about the anatomy and physiology of shoulder impingement (especially secondary), as well as the causes, let’s talk about how physical therapy can be used to address the issue. First it is important to address one’s posture, which can be done quickly and easily in one session with a physical therapist. In addition it is necessary to avoid shoulder movements that aggravate your shoulder pain. As stated above, if you continue to repeatedly impinge and already impinged shoulder you will aggravate your symptoms and make recovery longer and harder. With proper posture, your joints, muscles, and tendons are in a better position to function without over working. However, these structures are probably too tight, too stretched out, or too weak. It is important to strengthen the rotator cuff muscles to hold the humerus properly in place. Strengthening of the muscles that attach to the shoulder blade (trapezius, serratus anterior, rhomboids, levator scapula, and latissimus dorsi) which affect shoulder motion is needed to have the shoulder blade in the optimal position for the shoulder joint to achieve full motion. A physical therapist understands that stability and control of motion are just as vital if not more so than strength. Physical therapists can recognize any compensatory movements you may be using that are contributing to the pain as well as introduce exercises that will increase shoulder stability. If your capsule is too tight and causing pain, physical therapists can use various joint mobilizations to decrease the capsule’s stiffness. Shoulder strength, stability and control of motion along with modifying activities that aggravate your shoulder pain in the beginning phases of the inflammatory process are key. Addressing these issues will allow for full, pain free shoulder range of motion and prevent larger problems from happening.
If you have shoulder pain or believe you have shoulder impingement, visit Total Performance Physical Therapy.