Tuesday, April 5, 2011

Why do arthritic shoulders get stiff?

In contrast to a frozen shoulder, where the cause of stiffness is only related to tightness of the soft tissues, the arthritic shoulder is stiff because of the loss of the normal concave shape of the socket (the glenoid) and the normal convex shape of the ball (the humeral head). Compare the x-rays of an arthritic shoulder shown below to those of the normal shoulder shown in our March 22 post.

Here is the AP view showing the flattened humeral head and glenoid.

Here is the axillary view showing the socket wear and flattening of the joint surfaces. 

Here is a CT (Cat Scan) showing even better the irregular joint surfaces and the bone spurs on the back of the humeral head that block normal joint rotation.
When shoulder arthritis gets to this point, physical therapy and injections are unlikely to improve the function of the joint. Surgical treatment may be indicated to restore the roundness, stability and load transfer characteristics of the joint surfaces as well as balancing the soft tissues around the joint.


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