Cartilage Tears of the Shoulder
A Common Cause of Shoulder Pain in Both Athletes and Older Patients
Healthy cartilage is essential to proper shoulder movement. When common cartilage tears occur, pain and limited range of motion result.
Cartilage plays an important role in normal shoulder function. There are two types of cartilage in the shoulder. The first type, called fibrocartilage, lines the rim of the socket of the shoulder. This rim of cartilage, known as the labrum, acts to deepen the socket of the shoulder, increasing joint stability. Tears of the labrum result in vague constant shoulder pain, a clicking or catching sensation with shoulder movement, and shoulder joint instability. The second type of cartilage, called hyaline cartilage, covers the articulating surfaces of the shoulder joint, providing cushioning during joint movement. Damage to hyaline cartilage causes pain, and can result in arthritis.
Shoulder Anatomy
The shoulder joint is made up of portions of three bones – the upper arm bone, known as the humerus, the shoulder blade, known as the scapula, and the end of the collarbone, or clavicle. The head of the humerus acts as the “ball” of the ball and socket joint, and the glenoid fossa of the scapula acts as the “socket”. The shoulder socket is relatively shallow, which allows the shoulder joint to move in many different planes – in fact, the shoulder is the most mobile joint in the body. However, the same shallow socket that allows the shoulder its freedom of movement, also leaves it susceptible to instability and dislocation. The physiologic function of the glenoid labrum is to deepen the socket, adding to shoulder instability.
Types of Labrum Tears
SLAP tear:
The acronym SLAP stands for “superior labrum, anterior to posterior”. This refers to a tear of the labrum that involves the top (superior) part of the cartilage, and extends from the front of the shoulder (anterior) to the back (posterior). This type of injury most commonly occurs as the result of repetitive overhead motion, or trauma to an outstretched, overhead arm.
Bankhart lesion:
A Bankhart lesion is a tear of the front (anterior) of the gleniod labrum. It is generally the result of a dislocation of the shoulder. Usually, when the joint dislocates, the head of the humerus becomes displaced forward and down from the glenoid, knocking off the cartilage rim in the process. The injury results in pain, and instability. Once a Bankhart lesion occurs, the shoulder is susceptible to future dislocations.
Hyaline Cartilage Injury
Hyaline cartilage lines the articular surfaces of the shoulder joint. The humeral head (the “ball”), and the glenoid fossa (the “socket”) are both covered in cartilage, to cushion movement of the shoulder. The cartilage can become thin and irregular, due to “wear and tear” over time. If bare spots in the cartilage develop, this results in painful “bone on bone” movement of the joint. Eventually, further breakdown of the cartilage will occur, and arthritis of the shoulder will develop.
Defects in the cartilage can also occur from trauma to the shoulder. This type of fracture of the joint surface, known as an osteochrondral fracture, will usually hasten the onset of arthritis.
