I want to begin by saying that I am not a doctor. I don't even play one on the internet. My experience with biomechanics and anatomy/physiology stems mainly from my education - I'm a senior bioengineering student at the University of Louisville - and some research opportunities I have had through the University.
With that said, Demaryius Thomas' achilles heel injury is not to be taken lightly. Reports from all over the media are giving his recovery a timetable of 6 to 8 months, which is typical. Depending on the individual and/or poor medical care, it could potentially take upwards of 12 to 18 months. Since Demaryius Thomas will be receiving the best possible care and is a trained athlete in top physical condition, it shouldn't take quite that long. 6 to 8 months sounds about right, but keep in mind that we don't know all the details about the degree of the injury. We know that he "ruptured" his Achilles Tendon, but a rupture could mean a partial tear of the tendon or a full tear of the tendon (or a wide spectrum of severity in between). Since reports have surfaced that the injury will require surgery, one could assume it's a full tear or a severe partial tear... but you know what assuming does.
Yesterday, I received a twitter reply asking "What takes an achilles tendon rupture so long to heal?"
I attempted to answer the question on twitter, but because of the 140 character limit, I don't feel I gave that question it's due diligence. I shall answer that question in this post.
First, an introduction...
The achilles tendon is the largest tendon in your body. It is responsible for connecting the heel to the muscles of the lower leg. Contracting your calf muscles pulls the achilles tendon upwards, resulting in the foot articulating downwards. As a result, the achilles tendon allows a person to stand, walk, jump, run, or stand on your tip toes.
When it's torn, you're basically subjected to gravity. (You're gonna fall on your face.)
Why does it take 6 to 8 months to heal?
Wound healing comes down to one thing - cell production. If you can produce cells faster, you'll heal quickly. If you get a superficial cut on your finger, it will heal quickly because your body produces skin cells very rapidly.
But why do skin cells regenerate faster than tendon cells would?
It basically comes down to energy consumption - and I'm going to try my hardest to simplify it so that I don't lose anybody along the way.
Cell energy is due to ATP (adenosine triphosphate). That is cell energy "currency", if you will. The more ATP your cell can make, the more energy your cell has, and the faster it can reproduce to fill in the voided tissue. ATP is produced in the cell through processes such as glycolysis, the citric acid cycle and the electron transport chain. Glycolysis and the citric acid cycle can only produce a few ATP (2 each), while the electron transport chain can produce many more (32 to 36). Without getting into the meat and potatoes of what each cycle does, let me just say that the key to making the most energy possible is oxygen.
If you can introduce oxygen to a cell, your cell can undergo what is called "aerobic respiration". Basically, this means that your cell can do all 3 processes (glycolysis, citric acid cycle and electron transport chain). Without oxygen, your cells can only perform 2 of those processes (glycolysis and the citric acid cycle). This is less than ideal. Without oxygen, you're producing about 1/8 the energy that you would have produced with oxygen in the cell.
Why do I tell you all of this?
Well, as it turns out, your ligaments and tendons don't receive a lot of oxygen. Blood is how you transport oxygen throughout your body, but since the tendon doesn't have much vasculature, it doesn't see very much oxygen. Your skin, by comparison, has tiny blood vessels all over the place that constantly provide oxygen to your cells.
This is why a tendon injury will heal much slower than a superficial cut on your skin.
So, going back to answer the question, "Why does an achilles tendon take so long to heal?"... It just does.
Personally, I'd like to wish Demaryius Thomas the best of luck with his recovery. He should be back between August and October. To send along a 140 character encouragement, tweet to @DemaryiusT.