anatomy, informative

The Rotator Cuff – what’s inside my shoulder?

One of the most common issues that I see in the clinic is shoulder pain. I think it can really help to know the anatomy of the shoulder – in particular, the muscles of the rotator cuff. The rotator cuff is a term referring to the structures of the ‘glenohumeral joint’ – where the humerus (upper arm bone) meets with the scapula (shoulder blade). There are many structures located in and around the joint capsule, including cartilage, bone, ligaments and muscles.

There are four muscles in the rotator cuff (see IMAGE 1):
1. Supraspinatus
2. Infraspinatus
3. Teres Minor
4. Subscapularis


IMAGE 1. Rotator cuff (posterior view)

Each muscle plays a different role in movement at the shoulder (see IMAGE 2), for example: contraction of subscapularis causes internal rotation of the glenohumeral joint. In contrast, contraction of teres minor and infraspinatus both result in external rotation at the same joint, while supraspinatus is responsible for ‘abduction’ at the glenohumeral joint.

Shoulder Abduction Muscles Involved Shoulder Osteopathy Singapore
IMAGE 2. Movements at the shoulder

However, unlike the other three muscles of the rotator cuff, supraspinatus passes through a small space under the point where the acromion and clavicle meet – AKA the ‘acromioclavicular (AC) joint’. The space available in this area may reduce when you lift your arm overhead (abduction or flexion of the shoulder joint) due to movement of the structures inside and around the glenohumeral joint. In some cases, if there is not enough space for the structures of the shoulder to move effectively it is possible to experience an ‘impingement’. For more information about shoulder impingement check out the NHS website by clicking here.

Shoulder pain can be caused by many things, not just impingement. If you have shoulder pain and are unsure of the cause it is always worth asking for a professional opinion.

If you have experienced any problems with shoulder pain or movement and would like some help or advice, please feel welcome to contact Fiona today:
Phone: 07957 414 816


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