Protect Your Body: Shoulder Anatomy

For first responders, shoulders are put at risk in many situations.

Sometimes it’s from the strain of repeated tasks, such as pulling and hauling fire hoses or wielding an ax. Or it can happen in a split second, involving a forceful action, such as getting an arm yanked while trying to subdue a suspect.

Even something as simple as a common fall when a person lands on their arm, which happens to be in a slightly wrong position, can damage the shoulder.

Why do we see so many shoulder injuries? Because this structure in the body is inherently unstable due its architecture. The shoulder relies primarily on a system of musculature and ligaments that surround it for strength and stability. 

“Soft” tissues of the shoulder

We will concentrate on the “soft” tissues of the shoulder, which you can see in the illustrations above. We’ve also included links to “The Visible Body,” which is an awesome website offering 3D spinning drawings of anatomy, if you’re interested in another perspective.

  • Rotator Cuff is a group of four muscles – supraspinatus, infraspinatus, subscapularis and teres minor – that start at the scapula and attach to the humerus.  They hold the humerus bone firmly in the shoulder joint and assist with movement. Why is it important to know these muscles?Because the muscle most commonly injured in this area is the supraspinatus, and you’ll want to remember its name.
  • Labrum is a rim of rubbery cartilage that attaches to the shoulder socket. It provides cushion between the humerus and the joint, as well as adds stability. Injury to this tissue can sometimes lead to weakness and instability in the shoulder.
  • Biceps tendon is located in the front of your upper arm and runs along a groove in the humerus bone. The long head of the biceps tendon attaches to a small, bony protrusion on the humerus, crossing the labrum. Injury to or rupture of this tendon often can lead to an injury of the labrum.  
  • Acromioclavicular joint, known as the AC joint, is the structure between the clavicle and the acromion bones and is held together with ligaments. This joint can become a source of pain if swollen or separated.
Common injuries of the shoulder

There are, of course, many more components of the shoulder that come into play, but knowing those key four elements will help as we discuss symptoms of common shoulder injuries.

When we are talking about injuries, we are describing incidents that go beyond “regular” fatigue:

  • Rotator cuff injuries. More than 80% of rotator cuff injuries involve the supraspinatus muscle, which creates pinpoint pain on the outside of the shoulder or discomfort down the outside of the arm. You can also experience pain while rotating the arm to the outside, raising the arm to the side with or without resistance, raising your arm overhead or tucking in your shirt. 
  • Long head of biceps tendon injuries. Tears or tendinitis (inflammation) can easily occur in this tissue. Some symptoms include hearing a pop in the shoulder followed by bruising down the arm or balling up of the biceps. If you are unable to flex your arm at the elbow   or have significant pain (from a level 5 to 10, or greater) in the arm while trying to raise it, or turning door handles, using a tool (such as a screwdriver) or picking up an item, these can be symptoms of a biceps tendon problem.
  • Labral injuries. Tears and inflammation are common. Again, symptoms can include hearing a popping or locking sensation, reduced range of motion, as well as stiffness and weakness in your shoulder or feeling that the shoulder is unstable.

If pain limits your range of motion, prevents you from sleeping or your shoulder feels unstable – which I describe as a sensation that it feels like it is moving in and out without support – then you should see a physician.

We hope you’ve enjoyed this quick dive into the anatomy of the shoulder. Next week, join Rebound Lead Trainer Samantha Genno, when shee shares our favorite exercises to help prevent shoulder injuries.

Dr. Trent Nessler

Dr. Trent Nessler

President of Rebound Vitality - Innovative wellness for first responders

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