 Good day everybody. This is Dr. Sanjay Sanyal, Professor Department Chair. This is going to be a demonstration of the radius and the ulna, the bones of the forearm and the proximal and the distal radial joints. So I'm holding up the radius and the ulna of the left side. So this is the ulna and this is the radius. So let's take a quick look at the salient parts of each of these bones and then we shall talk about the proximal and the distal radial joints. So this is the head of the radius and this is the portion which articulates with the capitolum of the humerus to form the radio-humeral joint. Just under that we have the neck of the radius and below that you can see this bulge here. This is the radial tuberosity which gives attachment to the bicep tendon and just between the bicep tendon and the bone there is a bursa that's called the bicep's bursa or a radial bursa which prevents friction. Then we have the shaft. Now if you were to take a look at the shaft we will see that there's an anterior oblique line and there's a posterior oblique line. This anterior oblique line and the posterior oblique line they provide their demarcation between muscle attachments. Anteriorly and posteriorly above the anterior and the posterior oblique line we have the attachment of the supinator. The supinator is inserted there. Anteriorly anterior oblique line gives attachment to the flexor-digitron superficialis and theoretically it marks the upper limit of the so-called space of parona which is near the wrist. It also gives attachment to the flexor-polisus longus. Posteriorly it gives attachment to the abductor-polisus longus. As we come further down in the lateral aspect we have the impression for the proentoteris muscle. So the proentoteris muscle gets inserted there and there is also an attachment of the proentor quadratus further lower down. Then when we come lower down we notice that the lower portion is widened and we see that this is the portion which articulates with the carpal bones more specifically not with the bicep arm but with the lunate and the scaphoid bones and it forms the radiocarpal joint. This is the radial styloid process and this can be felt in the anatomical snuff box. You can feel it on the dorsal aspect we can see a tubercle here. This is called the dorsal tubercle of radius also called the Lister's tubercle and it acts like a pulley but the extensor-polisus is longer standard and this is occupied by the third compartment on the dorsum of the wrist. So these are some salient points about the radius. Now let's take a look at the ulna this is also the left side of this is the trochlear notch of the ulna which fits into the trochle of the humerus to form the humeral ulna joint. So therefore this is the coronoid process which fits into the coronoid fossa the arm is fully flexed and this is the olicron process which fits into the olicron fossa when the arm is fully extended. If you want to take a look on the lateral side you'll see a depression here. This depression is called the radial notch of the ulna which fits into the head of the radius and margins give attachment to the annular ligament and that forms the superior or the proximal radial ulna joint. The shaft of the ulna and then lower down this is the head of the ulna. The ulna head is lower down and smaller and this is the styloid process of the ulna and we can feel the head and the styloid process on the ulna side of our wrist. This is the place where the head of the ulna fits into a small depression on the ulna side of the radius. This is called the ulna notch of the radius. This is what forms the inferior or the distal radial ulna joint. In a cross section both these bones are approximately triangular. So therefore this is the interosseous border of the bones which give attachment to the interosseous membrane. This is the anterior surface. This is the posterior surface of both the bones and this is the medial surface of the ulna and this is the lateral surface of the radius. So this is how it looks like in a cross section and these are the two bones. Now let's take a look at the proximal and the distal radial ulna joint. The proximal radial ulna joint is here. This is how the proximal radial ulna joint is constituted. The head of the radius fits into a depression on the lateral side of the ulna and this is called the radial notch of the ulna and this is enclosed by a ligament called the annular ligament. And inside that the head of the radius rotates. So therefore the proximal radial ulna joint is called a rotate-tree type of uniaxial synovial joint. That's how it rotates during pronation and supination. And the axis of the rotation is an imaginary line going exactly through the center of the head of the radius. Distal radial ulna joint is this one. This is formed by head of the ulna fitting into a depression on the ulna side of the radius and this is called ulna notch of the radius. And here this is not a rotate-tree but this is a uniaxial pivot type of joint whereby when we pronate the hand the whole radius pivots around like this and it goes across. This is a plane x-tree in the forearm to show a pronated forearm where the radius is going across the ulna. And as it goes across because I told you the radius lower end articulates with the cardboard bones the lunate has scaffolded. The ulna cannot articulate with the cardboard bones because there is a triangular ligament called the articular disc which is attached. Apex is attached to the ulna-stellar process and the base is attached to the radius. So therefore using that articular disc of the triangular cartilage radius pivots around the ulna and it crosses over. So therefore the distal radial ulna joint is a uniaxial pivot type of joint. The axis of that movement occurs exactly between these two bones. So therefore if we were to take a line and join it with the top line through the center of the head of the radius and a point between these two bones that forms the axis of movement of pronation and supination. And to show the same thing here this is the articulated specimen that we see here. So when we do pronation and supination this is how it happens. The whole hand pronates and the whole hand supinates. And when the radius pronates it takes the cardboard bones and the palm with it. So this is pronation and this is supination. This is pronation and this is supination. So therefore the proximal radial ulna joint is a rotatory type of joint and the distal radial ulna joint is a pivot type of joint. At this juncture I will mention a few important clinical correlations. If you catch up a child by his forearm or his right hand and lift him up like we do affectionately we can cause dislocation of the head of the radius from the annular ligament. If it's a mild one it's called subclinical or clinical subluxation which can be reduced but if it's a major one it can get completely separated from the annular ligament and by the pull of the biceps it can get dislodged and that is called dislocation of the proximal radial ulna joint and that will require general anesthesia. In such a situation the radial nerve can be injured. We can have certain fracture dislocations. We have something called montegia fracture dislocation. In a montegia fracture dislocation there is a fracture of the upper end of the ulna and there is a proximal radial ulna joint dislocation. This is an x-ray of the forearm to show a montegia fracture dislocation fracture of the ulna and prug dislocation. There is another fracture dislocation which occurs distally and that is called the Gallia Z fracture dislocation. In Gallia Z there is a fracture of the distal radial ulna joint and there is a dislocation of the distal radial ulna joint. This is an x-ray of the forearm to show fracture of the distal radial ulna joint and dislocated distal radial ulna joint. Apart from that, there is a very common fracture which happens when an elderly lady falls on her outstretched hand. She can get a fracture of the distal end of the radius and it can be associated with the fracture of the ulnar styloid process. And the distal end of the radius, the fractured fragment, it dislocates and displaces dorsally. That is called Kori's fracture. And the deformity that occurs in the hand is when the person puts the hand across like this, you see a distinct bulge on the top. That is referred to as a dinner fork deformity, which is not a very uncommon injury. That is Koli's fracture of the radius. These are some of the points which I want to mention to you about the radius and the ulnar. Thank you very much for watching. Dr. Sanjay Sanyal signing out. If you have any questions or comments, please put them in the comment section below. Have a nice day.