Normal shoulder, shoulder arthritis

The Normal Shoulder

This is a cross-section of a normal left shoulder provided by my friend Chris Jobe. Front is up and the side of the body is to the right. The ball shaped object in the middle is the head of the humerus. The triangular object at the lower left is the glenoid socket. The reddish tissue on either side of the glenoid represent the rotator cuff muscles that hold the ball in the glenoid socket. The reddish tissue above and to the right of the humeral head is the deltoid muscle.

One can see how shallow the glenoid socket is - this allows of a great range of motion of the shoulder, but also puts the joint at risk for dislocation. Even though it is shallow, the glenoid concavity is critical to the stability of the joint. Note the thin layers of cartilage covering the joint surfaces of the humeral head and glenoid. It is this cartilage that enables smooth motion of the normal shoulder. It is this cartilage that is destroyed in shoulder arthritis.

The Arthritic Shoulder

The normally smooth surface of the humeral head provides an almost frictionless joint with the socket.

In arthritis, the surface is rough, devoid of cartilage, and surrounded by bone spurs, rendering the joint stiff and painful.

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You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty,  and rotator cuff surgery.

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X-rays for shoulder arthritis

In the normal shoulder, the ball of the humeral head and the glenoid socket of the scapula are covered with smooth articular cartilage. This cartilage gives the joint a coefficient of friction less than that of an ice skate on ice. It is this cartilage that is destroyed in shoulder arthritis.
Cartilage cannot be seen on X-rays, but the thickness of cartilage can be detected by observing the separation of the bones, the 'radiographic joint space'.


Let's take a look at how the shoulder should be x-rayed to diagnose shoulder arthritis and to plan a joint replacement.

In the shoulder, two X-ray views are essential for determining the 'joint space', the AP (anteroposterior) and the axillary views.

An AP view of a normal shoulder looks like this:

and an axillary view of a normal shoulder looks like this:

In each view one can see the separation of the ball from the socket due to the presence of cartilage in this normal right shoulder.

These views must be taken carefully to make sure that poor technique does not hide the true condition of the joint.

More about x-rays in arthritis can be found at this link.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

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Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link).

How to x-ray the shoulder (see this link).

The ream and run procedure (see this link).

The total shoulder arthroplasty (see this link).

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).