Table of Contents
Shoulder Girdle and Upper Limb
ANATOMY and MOVEMENT
Your shoulder girdle and upper limbs are essential for movement and function. They allow you to reach, lift, and perform a variety of tasks. Therefore, it is important to understand the anatomy and how they move to maintain healthy shoulders and arms.
Shoulder Girdle Anatomy
The Shoulder Girdle is made up of the:
The Clavicle is a long bone that goes from your Sternum (breastbone) to your acromion process (the top of the Shoulder).
The Clavicle connects to the Scapula by ligaments, muscles, and tendons.
Scapula (shoulder blade)
The Scapula or shoulder blade moves with the arm and Clavicle. It holds on to many of the muscles that move the arm.
Upper Limb Anatomy
The Upper Limb) is made up of:
Humerus (Upper Arm)
The Humerus is the long bone of the upper arm. It fits into the Scapula (shoulder blade) and connects to two other bones in your forearm (Radius and Ulna). The head of the Humerus is shaped like a ball that fits into the “socket” of the Scapula called the glenoid cavity. Together they form the shoulder joint (glenohumeral joint).
Radius and Ulna (forearm)
The forearm comprises two bones: The radius and the Ulna. The radius is on the thumb side of your arm, and the Ulna is on the pinky side of your arm. Together they connect with muscles, tendons, and ligaments to help move your wrist, hand, and fingers.
On the other end, they form the elbow with the Humerus. It is at this junction that Golfer’s Elbow and Tennis Elbow become problematic.
The radius helps with the lateral movement of the arm. The Ulna is longer than the radius. Together they are called forearm pronators. The radius does most of the moving when you move your wrist. For example, it moves back and forth in a circle when turning the steering wheel in a car.
The wrist is made up of 8 small bones called the carpals. They connect with ligaments and tendons to allow movement of your hand. The carpal bones move together (when you bend your wrist back and forth). The carpal bones move side to side when you spread your fingers apart.
A repetitive strain injury such as Carpal Tunnel Syndrome is a problem with the median nerve. It can cause tingling and pain in the thumb, index finger, middle finger, and part of the ring finger.
The muscles that are attached to the carpal bones are what move your fingers. One of these muscles is called flexor digitorum superficialis muscle, which bends your fingers at the knuckles.
Metacarpals are the bones in your palm. They connect with the tendons and muscles in your hand to allow movement. There are five metacarpals in each hand. The first metacarpal is the bone that connects to your thumb. The fifth metacarpal is the bone that connects to your little finger.
The fingers are made up of 3 bones, the proximal phalanx, middle phalanx, and distal phalanx. The proximal phalanges connect with the metacarpals. Together they make up your knuckles. The thumb has two proximal phalanges while the other four fingers have one each. The middle phalanges are more on the side of your finger and connect with the bones of your hand. Finally, the distal phalanx is at the end of your finger and is covered by a fingernail.
The thumb has a unique ability to move in all four directions. This allows for movements in every direction including, side to side, back and forth, up and down, in a circular motion.
The function of the Shoulder Girdle
The Clavicle moves with the Scapula and upper arm, allowing for movement in all directions.
The Shoulder is the main joint that connects the arm to the body’s trunk.
The structures that are involved in this joint include:
- bones (humerus, scapula)
- muscles (pectoralis major, supraspinatus),
- ligaments (acromioclavicular and coracoclavicular), and
- tendons (biceps, deltoid).
Movements of this joint include flexion, extension, abduction and adduction.
The Shoulder Girdle sits atop the rib cage with the only joint attachment between the Clavicle and the Sternum (at the front) being the Sternoclavicular Joint – allowing for limited movements in all directions. The other end of the Clavicle meets the Scapula at the outermost part, where we consider the Shoulder to be (Acromioclavicular Joint).
The two Scapula (shoulder blades) float flat, sliding along the back of the Rib Cage with muscle attachments providing the only positioning and support. This is known as scapulothoracic glide. This positioning allows for a more versatile structure than the pelvis, permitting a wider variety of movements.
However, this leads us to what can go wrong. Issues like Thoracic Outlet Syndrome can be influenced by the combined positioning of these joints.
What is scapulothoracic glide?
Scapulothoracic glide is a movement that occurs at the shoulder blade and ribcage joint. This movement allows for the shoulder blade to move along the rib cage, which increases the range of motion at the shoulder joint.
Signs of Scapulothoracic Glide Dysfunction
There are many symptoms of scapulothoracic glide dysfunction, including:
- pain at or near the scapula
restricted range of motion at the shoulder joint, which can be
- limited if there are any adhesion’s in the muscles around the scapulothoracic joint
- pain worsened by overhead motions, such as throwing a ball overhand or swimming
- any limitation in the arm and shoulder can indirectly impact the health and wellbeing of the neck. This can potentially lead to neck pain.
As an example
Imagine the Upper Trapezius, the muscle that sits on top of your shoulders at the level of your ears. Suppose this tightens and shortens as is easily possible in a stressful situation. In that case, the shoulder blades will lift, with the arms turning either in or out, leading to a change away from a ‘normal’ resting position.
Try this exercise. Lift your shoulders to your ears:
- What happens to your shoulders and arms?
- Where are your head and neck sitting?
- How are the muscles along your spine reacting?
When we think about the human body, it is easy to forget how intricate and complicated our skeletal system can be. For example, the shoulders are made up of many different joints that allow for a wide range of motion. This includes flexion, extension, abduction, adduction, and rotation in any direction.
SHOULDER and SCAPULOHUMERAL (Shoulder) JOINT
The Humerus meets the Scapula (shoulder blade) to form the Shoulder joint at the top, while at the lower end, it joins the Ulna and Radius to form the Elbow joint.
The Humerus sits precariously within the shallow ‘cup’ of the glenoid cavity. It is held in place through the relationship of muscle and ligaments working to support and stabilise movement at the Glenohumeral joint or Scapulohumeral joint. While shoulder design allows for an excellent range of motion, it also leads to postural instability and potential injury, such as shoulder impingement.
The precarious balance at the joint level can be impacted by how tilt and shift are present within the shoulder girdle. This causal relationship may inhibit any activity requiring a unique range of movement and task for the upper Limbs.
Finding a comfortable and protected environment from which effective and efficient movement is possible requires more than local release and/or strengthening.
What is the Rotator Cuff?
The rotator cuff is a group of muscles and tendons that surround the shoulder joint. These muscles and tendons help to lift the arm and rotate it in different directions.
The four muscles of the rotator cuff are:
- teres minor
The tendons of all four muscles combine together at the top of the shoulder to form a covering called the articular capsule.
At this point, it is important to note the relationship between the Rotator Cuff and the Scapula. The scapulae have a unique shape that allows for their position, mobility and range of motion. It also allows for the attachment points of muscles, which are essential to daily life activities that require upper limb usage.
The majority of injuries that impact the rotator cuff most often occur in sports where overhead movements are required—such as baseball pitching or tennis serving.
Rotator Cuff Injury:
The rotator cuff is a group of four tendons and muscles that surround the shoulder joint and allow you to raise your arm, reach behind your back, and rotate your upper arm in different directions. Any issues in the rotator cuff such as a tear in one or more tendons can result from injury, overuse, or aging. This can lead to severe pain and may require surgery to fix.