Detroit Tigers pitcher Joel Zumaya out for season with torn UCL
(So, before we begin, let me be clear that I am not Joel Zumaya's physician, have no access to any of his medical records or imaging, and am not privy to anything related to his injury diagnosis or subsequent treatment, and don't know anyone who does know or are involved in these things. His injury is being reported by multiple media outlets far more reputable than myself...so there ya go.)
It's been widely reported that Detroit Tigers pitcher Joel Zumaya has suffered a torn ulnar (medial) collateral ligament in his right (throwing) elbow. If you are even a slightly-above average sports fan, you know that this is the bane of all baseball pitchers. When you hear "An MRI today revealed a torn medial collateral ligament for so-and-so-hotshot-young-pitcher," it's usually followed by "...he will undergo Tommy John surgery and will be out for the season."
Let's talk about how the diagnosis is made. The patient (again, usually a pitcher) will give a familiar history of "feeling a pop in my elbow" after throwing a baseball, followed by pain and the inability to continue throwing. The thing that "pops" is the medial collateral ligament (MCL), which is the main stabilizer of the inner (or medial) side of the elbow when it is flexed. The ligament is stressed during valgus loading of the elbow (valg-huh? What did you just call me? Relax tough guy...here's an example of what I'm talking about).
Usually the ligament is not injured acutely...that is to say, it doesn't necessarily go from completely normal to injured with one fateful whip of the arm. The injury sort of builds over time, with the ligament getting repeatedly stretched with each pitch. Once the ligament is sufficiently weakened, there is the point of no return; the ligament tears (pay attention to the first five seconds of this video...and while I hate to continue to use Stephen Strasburg as an example, he is the most well known athlete in the last 2-3 years to have suffered this injury).
Usually an MRI follows: the normal MCL appears as a thin, straight band of tissue which attaches up high to the medial epicondyle of the humerus (the bony bump in the inner side of your elbow) and down low to the sublime tubercle of the coronoid process of the ulna. As with all ligament tears, what the radiologist is looking for is a gap, which the coronal images below show in another patient. In this case, the gap is located where the ligament is supposed to attach to the sublime tubercle of the ulna (arrow). If you've got a gap, you've got a tear.
The topic of surgical options, repair technique and rehab is well beyond the area of my expertise. Please go here, here and here if you want to learn more. Generally speaking, if you are an athlete who either is making money or wants to make money by throwing a ball, then surgical repair is the primary option. Reconstruction of the medial collateral ligament, also known as "Tommy John surgery", involves such things as harvesting a tendon from your wrist (the palmaris longus tendon) or a cadaver, and drilling holes into the elbow bones through which the tendon is weaved in place of the shredded native ligament...
...right, beyond the area of my expertise. This clip does a far better job of explaining it...and also gives a little background as to who Tommy John was and his relevance to this procedure.