Rob Gronkowski is going under the knife today for his third spine surgery. He is 27 years old. Fans understandably have questions and I’m going to try to answer them. These are the most common questions I’ve heard and read:

When did Gronk’s injury happen?

Yesterday as I was finishing up my office hours I was listening to Boston sports radio. All of the non-medical conjecturing about what happened drove me nuts. Did Gronk really get hurt on the Earl Thomas hit? Did the team force him back too soon (AGAIN) against the Jets? Was the Gronkowski family angry? It was like a bad episode of Grey’s Anatomy where none of the medical information made sense (FYI Scrubs was a much more accurate description of life as a doctor). I wrote down my thoughts on what most likely happened here and I’m pretty sure the Gronkowski family and the Patriots committed an act of plagiarism in their joint statement about what actually happened.

Gronk has had chronic low back issues for years. He had a disc herniation in college which caused pain, numbness and weakness in his legs and resulted in a microdiscectomy his junior year. Gronk continued to have some issues with his back after joining the Patriots and, during the 2013 season, since he was already missing time for a complicated forearm fracture, he decided to deal with his growing back pain by having a second microdiscectomy procedure on a different disc/level. Gronk has appeared to be in pain at multiple times this season, but up until recently it was manageable, as many chronic injuries are for active NFL players. Something changed acutely in the Jets game. I think it was when he layed out for Brady’s overthrown ball up the seam, others point to different plays. It doesn’t matter. Gronk’s disc issue likely went from a bulging disc that was manageable (only causing pain in his back) to a herniated disc that was pressing on nerves, causing pain in his legs. This “huge” change in symptoms corresponds to 1-2 millimeters in change of the disc. Gronk knew he couldn’t push through his pain any longer and that was when the decision was made to pull him from the Jets game and get an MRI. The MRI confirmed the disc herniation and nerve compression and he got on a flight to LA to have his third spine surgery with the world’s leading expert in microdiscectomies in athletes.

What is a microdiscectomy?

I wrote about spinal anatomy in pain-staking detail here, but it’s Friday and you probably have a lot of stuff to do so I’ll be more succinct. The spine is made up of bony building blocks called vertebrae (yellow on the drawing below). The vertebrae are separated by discs (in pink/purple). You can think of discs as being a lot like jelly donuts – more firm on the outside and jelly on the inside.

The normal disc at the top of the drawing is thick and uniform and doesn’t bulge. As stresses are applied to the spine the disc can get injured and start to bulge backwards (see “bulging disc” in the drawing). This can cause pain in the back but often that pain is manageable. After repetitive trauma and, despite Gronk’s best efforts to strengthen his back and core and work on flexibility, the disc can bulge more and some of the soft jelly inside of the disc (the nucleus pulposus) can herniate. This often causes compression of nerves as they exit the spine a mere millimeter or so away which leads to numbness, pain, and weakness of the leg(s), a condition called “lumbar radiculopathy.”

Gronk’s procedure today is likely another microdiscectomy. In this minimally invasive procedure, the surgeon locates the small disc herniation and removes the part that is pressing on the nerve(s) to relieve pain and weakness in the legs. That’s really it – not much more to it. During recovery, the athtlete is asked to rest so that the shaved-down disc can scar over to prevent it from re-bulging. The recovery is usually 6-8 weeks before the player can start to work back onto the field. Athletes are not usually back to 100% until 10+ weeks, however. Chances are exceedingly slim that Gronk will make it back on the field this post-season.

What does this mean for Gronk’s future?

A third lumbar (low back) microdiscectomy at the age of 27 is not a good thing, especially if you are a physical tight end in the NFL. Gronk is an immensely talented football player – there is simply nobody like him. Sadly, he will probably not have a long NFL career. His previous 2 discectomies were said to be at different lumbar levels – if I had to guess, L5-S1 (the lowest level of the lumbar spine) and L4-5. If I had to make an educated guess about his most recent injury I would say that it is likely a re-injury to one of those discs . I say that because 95% of disc herniations are at L4/5 or L5/S1.

Once players start having multiple discectomies at the same level they develop new issues. As surgeons remove pieces of the disc that are pushing on the nerve, the disc gets thinner, similar to the “thinning disc” in the above diagram. As this occurs, the vertebrae (bones in yellow) get closer together. As they grow closer together they start to rub on each other. This rubbing causes a new pain in the back and ultimately leads to osteoarthritis in the spine (see discs labelled “disc degeneration with osteophyte formation” in the above drawing). After two or three discectomies of the same disc you can now understand that a good portion of the disc would be removed. This would lead to so much pain and arthritis in the low back that surgeons generally recommend a spinal fusion. Gronk does not seem to be at that point yet. He has had 2 surgeries at 2 different levels. Spinal fusion involves fusing or “gluing together” a few vertebrae so that there is no motion in the spine and therefore no stress on injured discs and arthritic joints in the low back. A tight end would not be able to play his position with a spinal fusion because he needs the flexibility in the low spine to effectively block and receive catches. Sadly, if Gronk gets to a point that he needs a fusion, his career as an NFL tight end will be over.

Ok, well now I feel depressed. This happy, go-lucky, talented-as-hell 27 year-old guy who loves to play football won’t be playing much longer. How much longer? Nobody can guess. I think we’re probably talking years but it’s impossible to know. I don’t believe the Patriots are going to trade him in the short-term because of this most recent injury. I’ve seen a lot of convincing arguments to the contrary, but I think the talent and locker room presence they have in Gronk outweighs his current market value. One thing is for sure, Gronk will have an immensely successful career after football but it’s nothing he’s even considering in his hospital room today.

Follow me on Twitter @jessdeede