This is a tutorial on the elbow joint.   At the elbow joint, you’ve got three joints which are involved. You’ve got the humerus, the radius and the ulna.

There are actually three articulations involved with the elbow joint. You’ve got an articulation between the humerus and the ulna, so that’s the humeroulnar joint. You’ve got an articulation between the humerus and the radius. That’s the humeroradial joint. And you’ve also got an articulation between the radius and the ulna. This is a proximal radioulnar joint because you’ve also got a distal radioulnar joint.

 

There’s three bones involved and you’ve got three articulations.

 

We’ll just take a quick look at some of the features of the articulating surfaces of the bones before we move on to things like the joint capsule and ligaments.

 

The articulating area of the humerus has two parts. You’ve got the trochlea and the capitulum.   The trochlea is medial and this is articulates with the trochlear notch of the ulna. The capitulum is this bit here. This articulates with the head of the radius and this bit is lateral.   You’ve got the capitulum and the trochlea articulating with the head of the radius and the trochlear notch of the ulna respectively.

 

Just a few other points about the distal humerus which are worth noting. You’ve got three fossae. You’ve got the coronoid fossa here, the radial fossa here and on the back of the humerus, posteriorly, you’ve got the olecranon fossa – so three fossae. And you’ve got the epicondyle.   You’ve got the lateral and the medial epicondyles.

 

Let’s just take a quick look at the ulna and the radius.

 

I just switched over to an isolated view of the ulna. You can see this notch here, this is the trochlear notch and this is what articulates with the trochlea of the humerus. Just below this notch, you can see this depression here. This is another notch called the radial notch and this articulates with the head of the radius. This articulation, you get pronation and supination.

 

This little bit here is called the coronoid process. If I rotate the ulna posterior, this is the olecranon process.   Those are a few features of the ulna which are worth noting before I go on to talk about other features of the elbow joint.

 

I’ve just switched back to this view and you can see the head of the radius articulating with the ulna at that little notch I showed you, the radial notch on the ulna.

 

Now you can see the humeroradial articulation between the capitulum of the humerus and the head of the radius, the trochlea of the humerus and the trochlear notch of the ulna and the radioulnar articulation, the proximal radioulnar articulation between the head of the radius and the radial notch of the ulna.

 

What movements do we get at the elbow joints. Well, at the humeroulnar and the humeroradial joint, we get flexion and extension – so flexion up this way and extension back this way. The humeroulnar joint is a hinge joint and the humeroradial joint is a limited ball-and-socket joint.

 

At this point here, the proximal radioulnar joint, we get supination.   Supination is when the hands are in this position and the anatomical position of the hand is supinated. If the radius rotates over the ulna to bring the hands to face toward the body, that’s pronation.   We get pronation and supination at this joint here, the proximal radioulnar joint. This joint is a pivot joint.

 

Now we’ll just take a look at some of the other features of the elbow joint. We’ll take a look at the joint capsule and the ligaments.

 

You’ve got three ligaments basically. You’ve got the radial collateral ligament, the ulnar collateral ligament and the annular ligament. And then you’ve got a joint capsule, which can be separated into a fibrous and a synovial membrane.   We’ll just take a look at the joint capsule first.

 

I’ve just isolated the joint capsule and you can look at its attachments.   You can see it attaches to the medial epicondyle. It runs over the two fossae here, so over the coronoid fossa and the radial fossa. And then it attaches inferiorly on the neck of the radius and on the coronoid process of the ulna.

 

Posteriorly, the joint capsules attaches on the margins of the olecranon. You can see how it overlies the olecranon fossa.

 

Underneath the fibrous membrane, you’ve got the synovial membrane. The synovial membrane is separated from the fibrous membrane by fat pads.   If I just remove the fibrous joint capsule, the fibrous membrane of the joint capsule, you can see the fossae, the coronoid and the radial fossae.

 

If I drawn on the outline of the synovial membrane which lies roughly here, you’ve got fat pads which sit on top of it and separate it from the fibrous membrane. These fat pads, they sit over these two fossae, so they sit on this region here. And if I rotate the model around, you’ve also got a fat pad which overlies the olecranon fossa. These fat pads separate the synovial membrane from the fibrous membrane of the joint capsule.

 

The fibrous membrane of the joint capsule actually thickens medially and laterally to form the ligaments of the elbow.   Laterally, which we’re looking at here, you can see the joint capsule thickens and it forms this ligament called the radial collateral ligament. This ligament attaches on the medial epicondyle and then it also attaches to the radial notch of the ulna and it also extends inferiorly and blends with this ligament here, the annular ligament, which I’ll show you in a second.   That’s the radial collateral ligament.

 

Medially, you’ve got the ulnar collateral ligament, which is formed by a medial thickening of the fibrous membrane of the joint capsule. The ulnar collateral ligament attaches on the medial epicondyle and it extends down and attaches to the coronoid process of the ulna.

 

And if we just rotate the model around, we can look at the posterior extension of this ligament.   The ulnar collateral ligament also extends backwardly and attaches onto the olecranon.

 

The last ligament is that one I just mentioned, the annular ligament.   The word ‘annular’ comes from the Latin ‘annulus’, which means ring.   This ligament forms a ring around the head of the radius. This ligament, again, it blends with the radial collateral ligament and it also blends with the joint capsule.

 

This ligament is quite important because it holds the head of the radius in place and it allows the head of the radius to rotate on the capitulum of the humerus and also, it allows pronation and supination against the radial notch of the ulna.   You can see how the head sits in that radial notch. The head can rotate in this notch and is held in place by the annular ligament.

 

Those are some features of the elbow joint.   The things to remember are that there are three bones involved (the humerus, the radius and the ulna) and there are three articulations (a humeroulnar, a humeroradial and a radioulnar articulation) and you’ve got a joint capsule which consists of fibrous and synovial membrane.

 

The synovial membrane is separated from the fibrous membrane by fat pads which overlie the radial fossa, the coronoid fossa and the olecranon fossa.

 

The joint capsule thickens medially and laterally to form the radial collateral and ulnar collateral ligaments. And you’ve got the annular ligament which surrounds the head of the radius and allows pronation and supination and rotation against the humerus.

 

The movements you get at the elbow are flexion and extension at the humeroradial and humeroulnar articulations and at the proximal radioulnar articulation, you’ve got pronation and supination.

 

That’s the elbow joint.