Monday, October 19, 2009
The shoulder joint is an amazingly complex and fascinating structure. It needs incredible mobility and stability for it to function optimally. What I want to do is paint a clearer picture of the shoulder labrum, it's anatomy and function.
The shoulder joint is a ball and socket joint, similar to the hip, except for one thing, there is no bony socket. The humeral head rests in the glenoid fossa, which is essentially flat. This is where the labrum comes in. The labrum is essentially a fibrous structure that attaches to the glenoid and forms a concave cup. This creates up to 50% more contact surface for the humeral head, thus creating more stability. This is considered a passive structure. The glenoid humeral ligaments and joint capsule make up the other passive structures.
The rotatore cuff muscles are a dynamic stability system of keeping the humeral head in the glenoid fossa. Now when there is weakness or dysfunction with this dynamic system,t he static stabilizers are called on to do much more work, their load goes way up. After time, you can develop ligament laxity or even a labral tear.
O'briens is an orthopedic test, to test for a labral tear. Shoulder raised to ninety degree in sagital plane. Adduct the arm 10-15 degrees. Thumb down, arm straight. Apply pressure. Now, turn the palm so it faces up. Apply pressure. If there was deep pain with the first and either no pain, or superficial AC joint pain with the second, you may have a labral problem.
The best way to treat a labral problem, minus surgery is to really correct the movement pattern of your rotatore cuff/scapulae and restore strength. This will shift the load from the static to dynamic stabilizers.