How Abnormal Motion Patterns Cause Shoulder Injuries

Many shoulder problems are caused by abnormal motion patterns that occur as the body attempts to continue performing daily living activities while compensating for the effects of previous injuries. Some of the most common abnormal motion patterns that we see are caused by:

• Shoulder Joint Instability
• Abnormal Movements of the Shoulder Blade
• Restrictions in Internal Shoulder Rotation

Shoulder Joint Instability

Research has shown that extended periods of shoulder instability (glenohumeral instability) can start a cycle of micro-trauma and secondary impingement syndromes which often result in chronic shoulder pain. Practitioners will often find this type of instability during shoulder examinations and translation tests.

Anterior shoulder instability (laxity of the anterior capsule) is often related to problems in the posterior shoulder capsule. This combination of problems can have a considerable impact upon the structures of the shoulder’s kinetic chain

When the posterior shoulder capsule becomes tight, it affects the IGHL (inferior glenohumeral ligament). This ligament helps to maintain your shoulder’s position in the joint and acts as a supporting hammock or sling for the humeral head. When your IGHL does not function the way it should, your arm (humeral head) changes position, which can then result in a variety of impingement syndromes.

Abnormal Movements of the Shoulder Blade

Numerous studies have shown that abnormal motion patterns of the shoulder blade (Scapular Dyskinesis) can result in a variety of shoulder impingement syndromes. These alterations in muscle activity are often overlooked by clinicians when reviewing patients who have been diagnosed with a rotator cuff injury.

Abnormal shoulder blade motion typically causes an alteration in the muscle firing patterns of the:

• Upper trapezius (UT)
• Lower trapezius (LT)
• Serratus anterior (SA)

These abnormal motion patterns affect the patient’s ability to bring their shoulder forward or backward (protraction and retraction). A lack of backward motion (retraction) often leads to hyperangulation - a risk factor that can lead to shoulder impingements.

I believe that it is extremely important to restore normal motion patterns for the shoulder blade, since the presence of abnormal motion patterns substantially increases the probability of an injury reoccurring.

A practitioner who tests for and discovers alterations in normal shoulder motion can apply the appropriate Soft Tissue procedures and exercises to solve this problem.

Restrictions in Internal Shoulder Rotation

An increased risk of shoulder impingements is often associated with restricted internal rotation of the shoulder. This is especially true when an action requires the shoulder to be both flexed and internally rotated.

In this position, increased pressure is experienced between the insertion of the supraspinatus muscle and the acromion or coracoacromial ligament. This area often becomes the focal point of an impingement. For example:

• The supraspinatus muscle is a rotator cuff muscle that raises the arm to your side.
• The acromion is a part of the shoulder blade (scapula) that lies above the shoulder joint. The acromion articulates with the clavicle to form the acromioclavicular joint which is a common restriction point.
• The coracoacromial ligament is a strong triangular band on the shoulder blade, which with the coracoid process and the acromion, forms a vault for the protection of the head of the humerus.

Consequently, in cases where restrictions in internal rotation are noted (common with rotator cuff injuries), the practitioner should always look for and address impingements at these important focal points.

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