 So here's a 17-year-old with a pulling injury. Let's go somewhat basic. Here is the ulnar collateral ligament anterior band. Now here's an important concept. It has anterior posterior length. So you could rupture the front of it, or the middle of it, or the back of it. This is just the anterior band. It could be a full-thickness rupture, but it doesn't have to be complete from front to back. So some of the fibers in the back may still be there, some of the fibers in the front may still be there, or the entire front to back would be ruptured. So we could have a complete rupture from front to back, or we could have a rupture of the front fibers that would still be full depth. In other words, those fibers would be torn and retracted, and I'll show you in another projection. Now don't confuse this fact with the fact that there is another group or bundles of the MCL. There is an arcuate bundle of Osborne, and there's a transverse bundle, and those are not important. We're only concerned with the anterior posterior fibers and the proximal distal fibers of the anterior band of the UCL, which are right here. So now let's look at them in our most favored nation status projection, which is the coronal. So I've got a T1, proton density, water weighted, fat suppression sequence, and the gradient echo, which does a pretty good job with ligaments, but not so much with bone. Start out with a T1. At first glance, the anterior bundle of the UCL looks pretty good. It's got a somewhat straight, slightly arcuate turn where it inserts in the sublime tubercle of the ulna. It's got a broad base up higher, but remember, we're only on one cut, so we have to sweep all the way from front to back for the anterior band of the UCL, and let's do that. On the very next cut, it disappears, and on the very next cut, it still disappears. Where is our black band that should be sweeping from tightly the tip of the sublime tubercle, and then fans out more proximally? No, it's ruptured. It is ruptured at this locus, which is slightly to the back of the anterior bundle of the UCL. The entire proximal origin is off. It's still off, and there's dissecting blood into the UCL all the way to this tip, that bright signal as it approaches the sublime tubercle. Let me blow it up. That bright signal right there, that's abnormal. That separation of the UCL that should be snug as a bug in a rug on the sublime tubercle, that's also torn. So this is one very sick UCL. Let's sweep through it, and those of you that want to, you can gaze at the gradient echo image, which is a little bit thinner, but probably not as informative, but see that the UCL is not tightly adherent to the ulna. So this case is unusual, because at certain loci, the proximal end is off. At other loci, the distal end is separated or off, all focused on the anterior bundle of the UCL. Now in order to get this, you have to have a valgus force, which puts a stretch or a stress on this ligament, and it compresses the radius against the capitulum, sometimes leading to radiocapitular fracture. That did not happen here, fortunately. An example of an anterior bundle of UCL tear, and don't forget that this space right here, which is the superficial aspect of the UCL mechanism, is the flexor digitorum superficialis aponeurosis, which is layer number one of the medial collateral ligament, and it's got a bunch of blood and swelling in it, and that is what you're seeing right here.