The shoulder is an inherently unstable joint due to the architecture of the joint itself. Unlike the hip joint, a ball and socket joint, which has its stability provided by its bony structures, the shoulder relies primarily on the muscles and ligaments that surround it to provide its stability. As a result, it is more susceptible to injury, especially when someone is cranking it to its end range of motion. Because there is not bone there to stop the motion, the muscles and ligaments are the only restraint and thus are easily injured.
There are a lot of shoulder injuries that we see in grappling sports but for the purposes of our discussion, we will stick with the most common structures that are involved in the injuries we see most frequently.
The shoulder is primarily composed of the following bones: humerus (upper long arm bone), the scapular (shoulder blade), the clavicle (collar bone), and the rib cage. Although fractures do happen, it is more common to see injuries to the ligamentous and muscular tissues. As such, it is worth identifying these structures, what they are and what they do.
- Rotator Cuff - the rotator cuff is a group of 4 muscles of the shoulder which provide stability to the shoulder. The supraspinatus, infraspinatus, subscapularis and teres minor (pictured above). These muscles originate on the scapula and attach to the humerus. They hold the humerus firmly in the glenoid fossa (shoulder joint) so that you can move your arm around without having the humerus move in and out of the joint. Injury to these muscles can cause pain and excessive movement of the humerus within the shoulder joint. This can cause pain, decreased motion and lose of function. The muscle most commonly injured (>85% of the time) is the supraspinatus.
- Labrum - the labrum is the circular tissue depicted in the picture above and the humeral head is seated right inside that cup. The labrum provides a cushion between the humerus and the glenoid fossa and also provides stability to the shoulder. The way the humeral head is seated in the labrum in addition to the glenoid and capsule, the labrum provides stability to the shoulder. Injury to this structure can sometimes lead to instability in the shoulder.
- Biceps tendon - the long head of the biceps runs in the grove in the humerus (pictured above) and attaches to the superior (upper) portion of the labrum. Injury to this tendon and/or rupture of this tendon can often lead to an injury of the labrum.
- AC joint - the acromioclavicular (AC) joint is the joint between the clavical and the acromion (pictured above). This joint is held together via ligaments. This joint can become a source of pain if swollen or if separated. All AC seperations are not created equal. AC seperations are classified on a grading scale.
- costovertebral joint - the costovertebral joint is where the individual ribs attach to the spine. One of the common misdiagnosis in grappling athletes is a rib popping out. Typically if a rib pops out of place, this is at the costovertebral joint (located in the back - pictured to the right). This injury you will have a lot of pain with deep breath, coughing, sneezing and localized to the joint involved in the back. Often grapplers are told they have a rib out of place on the anterior (abdominal) region. This is more often then not a intercostal strain (muscle between the ribs) or internal oblique strain (pictured below).