What do the shoulder and hip joints have in common? A lot!
Both are ball and socket joints.
Both have a large outer group of muscles that are “powerful movers” with an inner group of “fine tuners” (we are familiar with the Rotator Cuff of the shoulder - the hip essentially has one too!)
Both share similar injuries (due to their similar structures). Impingement . Labral tears.
Understanding the intricacies of their structures as well as the specific way ways in which these joints move is, to say the least, essential.
So let’s talk about ball and socket joints. Ball and socket joints allow for the maximum amount of movement (greatest amount of Range of Motion).
With regards to joint mechanics, there is a combined SPIN as well as SLIDE/GLIDE of the “ball” portion on the “socket” surface during movement.
For example, when you raise your arm the ball (️humeral head) is spinning back (posterior) while simultaneously gliding down (inferior).
There are several factors that play a part in these precise mechanics. The joint capsule must allow equal movement in all directions and the surrounding muscles must perfectly counter-balance each other to suspend the humeral head perfectly with in the center of the socket (️glenoid fossa).
Imagine the alignment on your vehicles tires. If the alignment isn’t centered, they will wear unevenly. And this principle is true with any joint in the body! Unequal stress distribution or sloppy alignment where you are catching an “edge” (️the labrum) will result in WEAR and even TEAR!