Shoulder Anatomy 101
Your shoulders allow you to engage in many of the activities you love. As a large and complex joint, it allows you to move your arm in almost any direction, and to carry out important motions like throwing, pulling, reaching, and even waving to a friend. There isn’t a single sport that doesn’t require the smooth and pain-free function of your shoulders. This is exactly why a shoulder injury can impair so many aspects of your life.
Let’s unpack what it takes to make your shoulder function as it should – and how things can go wrong in the process.
What Makes Up Your Shoulder Joint?
Your shoulder bones and soft tissues work together to allow you to move it. Your shoulder is a ball-and-socket joint that connects your arm bone and shoulder blade. This type of fit is what allows such a great range of arm and shoulder motion, including front, back, up, down, and circular movements. It’s also what makes your shoulder susceptible to injury.
Your shoulder joint consists of three main bones: your arm bone, shoulder blade, and collar bone.
Your upper arm bone (humerus) has a ball-shaped area at its top (humeral head) that fits neatly into a socket-like cavity (glenoid cavity) in your shoulder blade (scapula). Meanwhile, your collar bone (clavicle) sits atop the joint, connecting your arm to your chest.
There are a variety of connective and soft tissue structures that help to stabilize your bones and allow for smooth, pain-free movement. For example:
- Tendons connect muscle to bone.
- Muscles power movement of your bones. In the shoulder, these include the biceps, deltoid, and rotator cuff.
- The rotator cuff is a group of muscles and tendons that surround the ball-and-socket joint of the shoulder and allow it to rotate. The rotator cuff is responsible for powering the majority of arm movements.
- Ligaments connect bone to bone.
- Bursae are fluid-filled sacs that cushion joints (and are located in the area between bone and the muscles/tendons that cause the bone to move).
- Cartilage cushions the areas where bones meet. In the shoulder, it also lines the “socket” area of the shoulder blade in which the “ball” of the upper arm rests.
- The labrum is a soft rubbery type of cartilage that surrounds the outer edge of the shoulder joint socket, which keeps the ball of your upper arm from sliding or popping out of the joint.
There are four main joints of the shoulder:
- Glenohumeral joint – the primary shoulder joint we have been discussing so far, where the glenoid cavity (socket) and humeral head (ball) meet. It allows a wide range of motion.
- Acromioclavicular (AC) joint – connects the clavicle to the acromion (atop the scapula), which itself connects to the deltoid muscle and allows shoulder abduction and flexion.
- Sternoclavicular joint – connects the clavicle to the breastbone. It allows the shoulders to move up and down in a shrugging motion.
- Scapulothoracic joint – connects the scapula and the rib cage, supporting the arms when performing push-ups or pull-ups.
Where Shoulder Problems Typically Arise
Most shoulder injuries begin with trauma during a fall, sports injury, or car accident. The damage can also occur little by little over time, as is the case with repetitive stress conditions.
Common injuries affecting the bones of the shoulder include fractures and dislocations. Soft tissue of the shoulder can tear, become inflamed, irritated, or otherwise damaged. Tendons, muscles, ligaments, cartilage, and bursa are all subject to these types of injuries. Degenerative conditions like arthritis and osteoporosis can increase your risk of a shoulder injury requiring medical attention.
Find out more about common shoulder conditions and what you can do about it:
- Shoulder instability
- Shoulder pain
- Shoulder arthritis
- Rotator cuff tears
- SLAP tear
- Bursitis – impingement syndrome
- Shoulder dislocations
- Acromioclavicular (AC) joint dislocation
- Scapular dyskinesis
- Frozen shoulder
Shoulder Surgeon in Knoxville and Athens, TN
Find out more about what makes a healthy shoulder – and how to restore function if you’ve suffered a shoulder injury. Call Dr. David Hovis at The Shoulder Institute at ORTHOKnox at (865) 251-3030 to schedule your consultation.