Shoulder impingement and pain syndromes

The above pain pattern can be a symptom of SAPS or Subacromial Pain Syndrome. SAPS is defined as all non traumatic, usually unilateral, shoulder problems that cause pain, localized around the acromion (top part of shoulder), often worsening during or subsequent to lifting of the arm (Diercks et al., 2014). The above scenarios fall under the external impingement subtype, which include compression or abrasion of muscle under subacromial space. People with impingement type pain often have altered shoulder blade movements as well. If left untreated, it will lead to more severe rotator cuff diseases.

Anatomy of the shoulder girdle complex

The shoulder refers to the union between scapula (shoulder blade), humerus, clavicle (collar bone) and its ligaments plus overlying muscles.

Here are some important bits you need to know:

1. The humeral head – This is the top portion of the bone in your upper arm. Normally it should stay snugly fit centered into its socket, the glenoid fossa
2. Acromion, Coracoid and Coracoacromial ligament – These structures sit above the humeral head and provide a small space aptly named the subacromial space.
3. Supraspinatus Tendon (part of the rotator cuff), long head of the biceps tendon and a bursa – These structures sit between the humerus and the subacromial space.  These are the structures that get impinged upon with this syndrome.
4. Shoulder muscles important for normal shoulder movement: deltoid, biceps, rotator cuff muscles
5. Scapular muscles important for normal shoulder movement: (upper/mid/lower) trapezius, serratus anterior and pectoralis muscle group

Efficient movement of the shoulder

While it may look like reaching up consists of the head of the humerus rolling upwards within the socket, the scapula and the clavicle actually plays an immensely important role in helping us reach. While the humerus rolls within the socket, the scapula upwardly rotates, posteriorly tilts, and the clavicle posteriorly rotates. Furthermore, shoulder girdle muscles (rotator cuff, trapezius, serratus anterior, pectoralis and biceps) have coordinated contraction and relaxation to help us with reaching. Certain muscle tendons will need to cross under the subacromial space in order to complete the motion.

Muscle imbalances and impingement pain

As mentioned above, patients with impingement pain often have different shoulder blade movements. Part of the problem can be due to the scapular muscles controlling the movement.  These include an overactive upper fibers of trapezius, tightness in the pectoralis and/or weakness in the serratus anterior.  Not only do changes within the scapular muscles cause changes to the movement of the scapula, they can also alter the orientation of the humeral head in its socket, thus decreasing the subacromial space during shoulder movement.  This can lead to compression of the rotator cuff tendons, bursa and the biceps tendon resulting in tendon pain.

Risk Factors for impingement pain

There are many common factors that influence the scapular muscles and can increase the chance of developing shoulder impingement syndrome.

Muscle timing issues

Full flexibility of the joints may be present, however there can be a problem where the muscles are not firing in the proper sequence.  This can be a result of muscle weakness or muscles that are too short and overpowering or too long and functioning as weak muscles.

Thoracic and cervical posture

Postural problems that affect the neck and thoracic spine can result in changes in the length/tension of muscles surrounding the spine.  This change in starting posture can affect the efficiency of scapular muscles.

Age and hand dominance

As we get older, our dominant hand’s shoulder girdle complex may also undergo degenerative changes which could increase the chances of developing SAPS.

Occupation

Jobs that require heavy labour and/or repetitive movements can predispose individuals to repetitive strain injuries in the shoulder girdle or scapular muscles, which can also lead to SAPS. Furthermore, sedentary workers could be at risk of developing SAPS if their desk is not setup ergonomically. Simple changes can be done to help alleviate these problems.

Previous traumas or injuries

Certain shoulder girdle injuries (ie. frozen shoulder, fractures and dislocations) can cause stiffness in the shoulder joint and its surrounding ligaments/capsules, which will have detrimental consequences to the efficiency of the scapular muscles.

Anatomical differences in the shape of the acromion

There are 3 common varieties of acromions found in the population. Certain types of acromions will decrease the subacromial space and may increase the chances developing SAPS.

What can be done?

Luckily, research has shown conservative treatments have favourable results in combating impingement type pain. Rehab professionals can help to identify underlying sources of why your shoulder isn’t moving the way it should. Part of the assessment should include a detailed history pertaining to previous injuries, medical conditions, occupation and social factors; followed by a careful analysis on how you move your shoulders.  A physiotherapist would then be able to offer a series of exercises to help restore the movement pattern. Often, this will be enough to reduce the initial pain. As your symptoms reduce, it will be important to address the next areas of mobility restrictions, postural changes or muscle imbalances that may have caused the initial symptoms in the first place.  Making positive changes in predisposing factors to injury will help prevent future re-injury.  Some of the possible interventions could include body weight exercises, flexibility programs and/or lifestyle modifications.

Not Sure Where to start?

You’re not alone. There are a number of risk factors that can prevent “traditional” shoulder and posture programs from succeeding.  Our physiotherapists and massage therapists have the experience and training to evaluate and diagnose your current status and the tools to get you started and progressing towards better health.  Contact us to get started on your goals!

References

Ludewig, P.M. & Braman J.P. (2011). Shoulder impingement: Biomechanical considerations in rehabilitation. Manual Therapy, 16, 33 – 39

Diercks, R., Bron, C., Dorrestijn, O., Meskers, C., Naber, R., de Ruiter, T.,  Willems, J., Winters, J., & Van der Woude, H.J. (2014). Guideline for diagnosis and treatment of subacromial pain syndrome, Acta Orthopaedica, 85:3, 314-322