What is my rotator cuff, and why is it giving me so much grief?
I imagine this is one of the most frequently asked questions on Google when people are looking up information on a painful and annoying shoulder. I also imagine this is why you’re reading this blog!
The shoulder is one of the most complex and fascinating joints in the human body, and with that comes a unique set of challenges that the shoulder has to deal with on a daily basis.
Today we’re going to deep dive into the anatomy and biomechanics of the shoulder and unravel the mystery of rotator cuff inflammation!
The anatomy of the shoulder To keep it simple, we’re going to be talking about the global anatomy of the shoulder and its key features. The shoulder is what we call a multiplanar joint (it can move in many directions) and thus is the most mobile joint in the body.
The shoulder can achieve close to 360 degrees of motion due to there being minimal structural stability in the form of bones and thus relying on active and passive restraints (muscles, ligaments, capsules, etc.) to provide stability.
The shoulder is unique, as the musculature must provide BOTH stability and power to help initiate and complete movements. With this in mind, the shoulder is one of the most complex joints in the body.
The bones of the shoulder
The shoulder is made up of three main bones:
Humerus — the upper arm bone
Scapula — the shoulder blade
Clavicle — the collarbone
These bones meet at three joints:
The glenohumeral joint, where the head of the humerus fits into a shallow socket in the scapula called the glenoid fossa. This is the main joint responsible for arm movement.
The acromioclavicular (AC) joint, where the top of the scapula (acromion) connects with the clavicle.
The sternoclavicular (SC) joint, where the clavicle connects with the breastbone (sternum).
The glenoid fossa also has a ring of fibrocartilage around it to help deepen the socket of the shoulder to make sure the head of the humerus fits nice and snug. This ring is known as your glenoid labrum.
Ligaments holding it all together
Ligaments are tough bands of tissue that connect bones to other bones. In the shoulder, they help keep the joint stable.
Key ligaments include:
Glenohumeral ligaments (superior, middle, and inferior): these ligaments help hold the humeral head in the socket.
Coracoclavicular ligaments (trapezoid and conoid): these connect the clavicle to part of the scapula called the coracoid process and help stabilise the AC joint.
Coracoacromial ligament: forms a protective arch over the shoulder joint.
Transverse humeral ligament: helps hold the biceps tendon in place on the humerus.
Muscles and tendons – our stabilisers
Surrounding the bones and ligaments are muscles and tendons that allow the shoulder to move and stay stable. Let’s start with the stabilisers.
The most important group is the rotator cuff, which is made up of four muscles:
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
These muscles help keep the head of the shoulder centred in the socket and, ultimately, a stable and happy shoulder. The rotator cuff muscles are small in nature and often vulnerable to being overloaded with repetitive movements, particularly overhead. Does this sound familiar?
The scapula (shoulder blade) stabilisers are key muscles that support shoulder movement and maintain proper shoulder mechanics. These include the
Serratus anterior
Trapezius (upper, middle, and lower fibers)
Levator scapulae
Rhomboids
Their main role is to hold the scapula (shoulder blade) in the correct position against the rib cage during arm movement. This stability allows the shoulder joint to function efficiently and prevents excessive strain on other muscles and tendons, especially the rotator cuff. Weakness or poor control of these muscles can lead to shoulder pain, reduced mobility, and increased risk of injury during daily activities or sports.
Muscles and tendons - the movers
With the stabilisers of the shoulder and the scapula working effectively, it will allow the rest of the muscles around the shoulder to focus on producing power! These muscles include:
Deltoid—its main job being to lift the arm up to its full overhead position
Latissimus dorsi—our biggest pulling muscle that draws the shoulder back and down to lock in for maximum power and stability
Pectoralis major—our biggest pushing muscle to help push objects away and draw them towards us.
Given that the shoulder is a highly mobile and complex joint, it is vital that the supporting cast of muscles are working synergistically to maintain a happy and healthy shoulder. Rotator cuff-related shoulder pain is often due to a combination of muscles around the shoulder not working to their full potential, causing the tendons and muscles of the rotator cuff to become overloaded and inflamed.
Keep your eye out for part 2, where we will dive headfirst into supportive shoulder exercises to help keep your shoulder pain at bay!
Disclaimer: This article is created and published online for informational purposes only. It is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice.
