 This is a 52 year old man who complains of medial wrist pain and a burning sensation while shoveling and doing yard work one month ago. I don't have that problem because I'm not very good at shoveling snow and I'm terrible at doing yard work. Nevertheless, they were concerned about a triangular fibrocartilage tear, which he has. I always like to start out in my search pattern in the coronal projection. I look at the relationship of the carpal bones. I see how inflamed the joint is. It's pretty inflamed. I look at the shape of the radial styloid, the ulnar styloid, which look normal. I look at the overall volume of the carpal bones, which are all normal with one exception. The lunate is abnormal. It's slightly decreased in overall height and it's undulated. I look at the scapholunate ligament and the lunato-trequitril ligament and just as important, perhaps more important, I look at the intervals to see if they are arthritic, diastatic, inflamed, hyper intense, and or eroded. And really, they're not. Perhaps there's a little irregularity at the scapholunate interval, but not much else. I observe the triangular fibrocartilage for its overall volume or height. In this case, it's about average volume, but it has some complex signal alteration in its central and inner third, consistent with a complex triangular fibrocartilage tear. So they were right. There's also a small chondral melasic erosion as evident by this very subtle area of subchondral edema in the ulnar body. There's quite a bit of inflammation along the periphery or ulnar aspect of the TFC or TFCC with some distention of the peripheral ulnar recess. But that, unfortunately, is not the main finding in this case. By the way, there is a limb of the small, often diminutive lunato-trequitril ligament, which is intact. The main finding in this case is the lunate. The irregular, reet-like, surpigenous signal intensity in the lunate, which is remodeled, slightly decreased in overall size or height, and therefore partially collapsed, is indicative of Keenbox disease or avascular necrosis of the lunate. So let's look at some of the appearances of the lunate. We'll draw a little bit here. Let's have a look at the relationship of the capitate, which I have up here on the right-hand side, with the lunate, which is a semi-lunar structure, and the radius, which I've drawn in green. So if we start to get a little bit of sclerosis, we'll color it in with green, that may be one of the early signs of avascular necrosis. In fact, David Lickman in 1977 gave a grading system, which is most commonly used on plain film, Dave Askin and Necrosis. So one would be a normal x-ray, two would be sclerosis. Three would be claps and fragmentation. And on the MRI, to your right, we have that. We have claps, we've already seen that in the coronal projection, and fragmentation with two diastatic lunate fragments. We can further divide this stage three, Lickman stage three up into, and by the way, we're extrapolating from plain film to MRI, 3A, where the radio scaphoid angle is less than 60 degrees. Let's try and draw the radio scaphoid angle. See if I can do it. There we are. There's the scaphoid. So we go down the long axis of the scaphoid. I'll even do it with my pen, down the long axis of the scaphoid. Then the long axis of the radius. And this angle should be less than 60 degrees in a 3A. But when the scaphoid starts to sag or rotate in a clockwise fashion, this angle is going to increase to greater than 60 degrees. And now we have a Lickman stage 3B. Stage 4 would be fragmentation with intercarpal arthrosis and erosions and radiocarpal articulation, erosive change. Now what else can happen? Let's get out of our coloring tool here. What else can happen in Keenbox disease? Well, because the lunate starts to become misshapen and collapses and fragments, the intrinsics may start to fail, especially the scapholunate ligament. When that occurs, the lunate will start to drift off to the ulnar side. This is known as ulnar translocation of the lunate. Now why does this condition occur? It most likely occurs due to friction in patients that have an abnormal biomechanical relationship between the radius and ulnar. There's more pressure against the lunate. This likely occurs because there's more pressure between the radius and the lunate. This likely occurs in patients more frequently who have negative ulnar variants. In other words, the ulnar is back here. Let's draw a little bit again. If the ulnar is proximal, that means the radius is pressing harder against the lunate, and therefore it's interrupting its blood supply, which is more robust along the palmar versus the dorsal aspect of the lunate. And by the way, there's intra and extraosseous blood supply to the lunate. So as this friction occurs, most likely due to misshapen bones or dysplasia, the blood supply is interrupted on a repetitive traumatic basis, not usually with a single traumatic event. And that's what's occurred here. Our patient was outside shoveling, and they subsequently developed Keembox disease. There are several different shapes of the lunate, too. There is a faceted shape of the lunate, there is a shape where the center of the lunate has a triangle at the base of it, and so on. And that will be a story for another day. But perhaps those intrinsic variations and shapes, along with the variance or position of the ulnar, further contribute to the development of Keembox disease. Now, let's log out of our color program for a moment and take a look at the short axis view. When a patient has Keembox disease and there is fragmentation, there is our fragmentation right there, bright signal intensity line between a volar palmar segment and a dorsal segment, the lunate may start to sag forward. The capitate may also start to sag forward, although that hasn't occurred here. But the lunate has. And as the lunate presses against the structure's anterior to it, it may compromise the carpal tunnel space. It may make it more narrow. Generally, the carpal tunnel space is a deep carpal fat pad and fat in between the flexor tendons. We see virtually no fat in this carpal tunnel, and there is a little bit of palmar bowing of the flexor retinaculum. And one last take-home point. On a T2 spin echo, or fast spin echo, without fat suppression, which this is, the median nerve should not be brighter than muscle. And it is. We take a piece of muscle, that's muscle, and that is the median nerve. The median nerve should look like this, not this. So that, that median nerve, which by the way is bipid, is under pressure. It's under siege from the volar sagging lunate in Keenbox disease. So in summary, this is a patient with stage 3A, or Lickman 3A Keenbox disease. The intrinsics are preserved. There's no ulnar translocation of the lunate. There is some collapse and fragmentation. There's volar displacement of the lunate leading to signs of secondary carpal tunnel syndrome. And as was suspected clinically, the patient does have a triangular fibrocartilage tear, but I sincerely doubt that that's the cause of the patient's main clinical syndrome of wrist burning as a manifestation of chronic friction from his shoveling event.