Radioulnar Joints

00:01 Now, let's have a look at the joints between the radius and the ulna.

00:05 Let's start by looking at the radio-ulnar joints proximally.

00:08 And then, we'll move on and have a look at them more distally.

00:12 So, if we look at the proximal radio-ulnar joint, this is really occurring between the radius and the ulna.

00:18 Here, we've got the radial notch of the ulna and that's where the head of the radius, its medial surface can articulate.

00:24 Here, we can see the head of the radius and it's important that we have this articulation to support pronation and supination.

00:31 Again, it's covered within the joint capsule of the elbow joint and it's reinforced, as I mentioned previously, via the annular ligament. And that allows supination and pronation to occur.

00:42 Distally, we have, again, an articulation between the head of the ulna and the ulnar notch of the radius.

00:48 So, here, we can see very small bony prominences articulating with each other at the distal aspect.

00:55 So, the head of the ulna is articulating with a little notch at the end of the radius, so called the ulnar notch.

01:03 Here, we can have articular discs and these go on to form articulations with the carpal bones which we'll come to in a moment. And most medially of the distal and of the ulna, we see the styloid process of the ulna there. And that's enabling articulation with those carpal bones.

01:18 We'll come to that in a moment or two.

01:21 Reinforcing the capsule around this distal joint, we have the dorsal radio-ulnar ligament.

01:26 That's helping to hold those bones together.

01:29 And here, we have the palmar version of that same ligament here on the palmar surface, reinforcing the connection between those two bony points.

01:38 The radioulnar joints really permit an important movement which is supination and pronation.

01:44 So, here, we can see we have the radius and the ulna sitting alongside one another.

01:50 This is as if you're looking at the anterior surface of someone with their palms facing forward.

01:55 Supination is the process of the radius crossing over the anterior surface of the ulna, so, you're now in a pronated position.

02:04 And then, if we return that back to the supinated position, you'll see your palm is facing forward.

02:09 It enables both your palm to face forward when you're supinating.

02:12 And then, the dorsal aspect of your hand to face forward when it's fully pronated.

02:19 If we then look at the interosseous membrane, that plays an important part in stabilizing this joint, holding the radius and the ulna together. It has a free margin at the top where the anterior interosseous artery passes over and it also has a circular aperture at the bottom, associated with the posterior interosseous artery that we've spoken about before.