‘What causes my Shoulder Pain?’

There are a many injuries to the shoulder joint varying from Impingement Syndrome to a rotator cuff tear and even a Dislocation of the joint. This article discusses the common shoulder complex weaknesses that can lead to such shoulder injuries and the how these same weaknesses need to be strengthened when rehabilitating the shoulder joint back from Injury.

Is there a strong Force Couple Relationship of Shoulder Joint Muscles?

One common feature seen in problematic shoulder joints is the excessive forward translation or movement of the humeral head (see illustration) into a forward lying position. This weakness or dysfunction comes about due a failure of the Force Couple relationship that exists between muscles of the shoulder joint. A force couple relationship involves two muscles on opposite sides of the shoulder joint, performing movements in opposite directions to each. An example is the subscapularis muscle that attaches to the front of the shoulder (humeral head) which is responsible for turning our arm inwards towards the chest and Infraspinatus muscle that attached behind the shoulder joint and which turns the arm outwards. It is this torsional stress or pull that these muscles exert on the joint during movement that creates a stabilising balance in the shoulder joint that help prevent instability or forward tilting of the humeral head. This dynamic balance is continually being tested during overhead activities such as painting, playing tennis etc.

If there is an imbalance in one of these opposing force couple muscles then dysfunctional shoulder joint movements can occur, leading to impingement syndrome which is very common in all age groups. In addition Shoulder joint dislocations are end products of a break down in the force couple relationship. Hence, Rehabilitation of shoulder injuries needs to focus on identifying a weakness in the force couple relationship and implementing exercises that will strengthen the weak shoulder muscles.

Importantance of Strengthening Shoulder Blade Muscles

Strengthening the muscles of the shoulder blade is something that we regularly ignore causing poor forward leaning posture, a sick dysfunctional scapula (shoulder blade) which lead to shoulder problems. Indeed it is these muscles that help move the shoulder blade and it is the shoulder blade or scapula that contains the glenoid socket that forms part of the ball socket complex that is the shoulder joint. Hence weak and tight scapula muscles can lead to restriction between the glenoid socket and humeral head (the shoulder joint), thus highlighting the importance of strengthening the shoulder blade muscles.

Tomás Ryan is a Registered Physical Therapist with The Irish Association of Physical Therapy and is based in Thurles.

Contact Number: 0504 26672

Email your queries to: tomaspryan@gmail.com

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Physiotherapy & Injury Rehabilitation Clinic in Tipperary

0504 26672


The Surgery, Fianna Road, Thurles


Riverside Medical Centre, 7 Upper

Irishtown, Clonmel

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Receipts are provided after each treatment for tax or health insurance companies.