Throwing Injuries

What Causes Rotator Cuff Impingement?

Rotator cuff impingement and bursitis causes have primary (structural) and secondary (posture & movement related) causes.

Primary Rotator Cuff Impingement – Structural Narrowing

Some of us are born with a smaller sub-acromial space. Conditions such as osteoarthritis can also cause the growth of sub-acromial bony spurs, which further narrows the space.

Because of this structural narrowing, you are more likely to squash, impinge and irritate the soft tissues in the sub-acromial space, which results in bursitis or rotator cuff tendonitis.

Secondary Rotator Cuff Impingement – Dynamic Instability

Impingement can occur if you have a dynamically unstable shoulder.

Dynamic shoulder instability means excessive joint movement, ligament laxity and muscular weakness around the shoulder joint.

This impingement usually occurs over time due to repetitive overhead activity, trauma, previous injury, poor posture or inactivity.

In an unstable shoulder, the rotator cuff has to work harder, which can cause injury.

An overworking rotator cuff fatigues and eventually becomes inflamed and weakens due to pain inhibition or tendon tears.

Typically, when your rotator cuff fails, it cannot prevent the head of the humerus (upper arm) from riding up into the sub-acromial space, squashing your bursa or rotator cuff tendons.

Failure to properly treat this instability causes the injury to recur. Poor technique or bad training habits such as training too hard is a common cause of overuse injuries, such as bursitis or tendinopathy.

More Info

• Bursitis Shoulder
• Shoulder Impingement

What is Scapulohumeral Rhythm?

Your shoulder-scapula joint motion has a regular functional motion pattern known as scapulohumeral rhythm - to provide you with pain-free and powerful shoulder function. When elevating your shoulder overhead, roughly one-third of your shoulder motion occurs at your scapulothoracic joint. Two-thirds of movement occurs at the glenohumeral joint, or 'true" shoulder joint. However, the timing and coordination of your shoulder muscles and how they control your scapulohumeral rhythm are essential factors.

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Alteration of this regular scapulohumeral movement pattern results in shoulder injuries, pain and impingement.

When your scapulohumeral rhythm becomes abnormal -due to pain, weakness or muscle incoordination - you are more likely to suffer shoulder clicking, pain or rotator cuff injury.

Shoulder Joint Anatomy

Your shoulder motion occurs via a complex group of joints that dynamically controls the movement of three bones (scapula, humerus and clavicle) upon your ribcage. Your shoulder blade (scapula) is the centralised triangular base for your shoulder and arm movements. Your scapular muscles guide your scapula as it articulates around your rib cage. This motion is known as scapulothoracic motion.

Your clavicle or collarbone is the only skeletal attachment of your arm. It attaches to your upper sternum and the lateral edge of your scapula at the acromioclavicular (AC) joint. Your shoulder ball and socket joint is the glenohumeral joint where your upper arm bone (humerus) articulates on the glenoid fossa of your scapula.

What are the Symptoms of Abnormal Scapulohumeral Rhythm?

Poor shoulder blade stability results in abnormal tipping and rotation of your scapular, which causes your acromion (bone) to pinch down into the subacromial structures (e.g. bursa and tendons), causing impingement leading to swelling or tears. Typically signs of abnormal scapulohumeral rhythm include shoulder pain, instability and clicking. Researchers have identified abnormal scapulohumeral rhythm as a major cause of rotator cuff impingement.

Your shoulder physiotherapist is an expert in the assessment of scapulohumeral rhythm. They will observe your shoulder motion and perform strength and control tests to assist their diagnosis. X-rays, MRIs, ultrasound scans and CT scans cannot determine scapulohumeral rhythm dysfunction.

Why is Scapulohumeral Rhythm Important?

Poor scapula stability usually results in tipping and downward rotation of your scapula. The downward posture causes your shoulder (tip of acromion) to pinch down on the subacromial structures. Rotator cuff impingement, shoulder bursitis or rotator cuff tears result from subacromial impingement.

Normal shoulder blade-shoulder movement - (scapulohumeral rhythm) - is required for a pain-free and powerful shoulder function. Luckily, abnormal scapulohumeral rhythm can be retrained by an experienced shoulder physiotherapist.

Scapulohumeral Rhythm Correction

Your skilled physiotherapist can assess and correct your scapulohumeral rhythm. Any deficiencies will be an essential component of your rehabilitation. Among other treatment options, teaching you how to control your shoulder blade via scapular stabilisation muscles is crucial for a successful recovery.

Your physiotherapist will be able to guide you in the appropriate exercises for your shoulder.

Restore Normal Neck-Scapulo-Thoracic-Shoulder Function

You may find it challenging to comprehend that your neck and upper back (thoracic spine) are essential in treating shoulder pain and injury. Neck or spine dysfunction can not only refer to pain directly to your shoulder but can affect a nerve's electrical energy supply to your muscles, causing weakness.

Plus, painful spinal structures from poor posture or injury don't provide your shoulder, or scapular muscles, with a solid pain-free base. In most cases, especially chronic shoulders, some treatment directed at your neck or upper back may ease your pain, improve your shoulder movement and stop pain or injury from returning.

For more information, please consult your shoulder physiotherapist.

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