According to one source, the Mets found a Ulnar Collateral Ligament (UCL) problem in Kay's left elbow. Here is what the American Academy of Orthopaedic Surgeons says about Kay's injury:Per @jimcallisMLB, @Mets sign 1st-rounder Anthony Kay for $1,1m ($1,972,100). Bonus Tracker: https://t.co/BefycBKbIx pic.twitter.com/ij32p0j3DA— MLB Pipeline (@MLBPipeline) July 13, 2016
The ulnar collateral ligament (UCL) is the most commonly injured ligament in throwers. Injuries of the UCL can range from minor damage and inflammation to a complete tear of the ligament. Athletes will have pain on the inside of the elbow, and frequently notice decreased throwing velocity.The AAOS states that "In most cases, treatment for throwing injuries in the elbow begins with a short period of rest." Other nonsurgical treatments include a lengthy period of rest, physical therapy, changing how he throws when pitching, and anti-inflammatory drugs. "If nonsurgical treatment is effective, the athlete can often return to throwing in 6 to 9 weeks" . . . [but] "Athletes who have an unstable or torn UCL, and who do not respond to nonsurgical treatment, are candidates for surgical ligament reconstruction," better known as "Tommy John surgery".
Here's some info from the AAOS on the surgery:
To surgically repair the UCL and restore elbow strength and stability, the ligament must be reconstructed. During the procedure, the doctor replaces the torn ligament with a tissue graft. This graft acts as a scaffolding for a new ligament to grow on. In most cases of UCL injury, the ligament can be reconstructed using one of the patient's own tendons.It appears that the Mets will not have Kay pitch this season. Hopefully, that and whatever other nonsurgical treatments he gets will enable him to resume pitching in games by next spring.