(Update: after publishing this, reports confirmed that Adrian Peterson would miss 3-4 months. It is clear that Peterson must have suffered injury to the portion of the meniscus that has little blood supply and needs surgery to repair. I had already suggested that this may be the beginning of the end, but with this news it may just be THE END!)
Adrian Peterson is reported to have a right knee meniscus tear and the timetable for his return seems to be unclear. Many of the injuries we see in the NFL have little tells and clues that allow me to make a very educated guess on how it will play out, but a meniscus tear may be one of the trickiest injuries to forecast without explicit details.
There are two menisci in the knee, the medial meniscus (inner part of the knee) and the lateral meniscus (outer part of the knee). These structures are fibrocartilage that basically serve as the pillows for the knee-joint and act as joint stabilizers. When the knee is straight, the menisci are typically at little to no risk as they are safely tucked into the knee-joint space. As the knee transitions to a bent position (usually for a squatting or lunging like motion) while the foot is in contact with a surface (usually the ground), the menisci assume a position in which they seem to peek out of the joint. During this peek is when most meniscus injuries occur. Adrian Peterson demonstrated this well if you watch the position of his right knee as his injury occurred.
The problem with speaking about a meniscus injury that you do not have intimate knowledge of is that the variables are countless. The details of the tear is important with a meniscus, as the inner 2/3 of the meniscus is avascular, meaning it has no blood supply. The outer 1/3 has blood supply and therefore typically has a better healing prognosis. Aside from the site of the tear, the size of the tear and the subsequent position of the torn tissue are other factors that play a big part in giving a prognosis for recovery.
I can see how some may believe that Mike Zimmer is just playing injury report games by not ruling Peterson out for next weeks game vs. the Carolina Panthers, but meniscus injuries have a broad enough range that Peterson could play next week or this could effectively end his career. The answer is likely somewhere between.
The fact that surgery has not been mentioned suggest that this is likely an injury to the vascular outer third of the meniscus, which means there is a chance that Peterson will only need conservative interventions such as Physical Therapy and modalities to heal. On the other hand the optics of Peterson being carried out, being unable to even touch the ground with his right foot leads me to believe the tear may be more significant. I have treated patients who are in and out in a matter of weeks for meniscus injuries, patients who take months to get back on track, and the worst are the ones who you think are healed and months later they’re back. When a meniscus is torn it may have significant symptoms such as pain and clicking which is usually the torn tissue getting caught in the knee-joint as the joint bends and straightens, but for some the torn tissue is in a good spot and doesn’t cause any interference with joint movement. The most annoying part about a meniscus is sometimes you get both sets of symptoms. One day there is no clicking and no pain, and one squat or bend later, the torn tissue is caught between the femur and tibia and the patient can’t stand to bend their knee.
The meniscus has an annoying quality of re-injury and symptom fluctuation. Based on the position of the cartilage and its peekaboo type movements during bending, many people who have to return to repetitive bending activities will eventually catch the meniscus peeking too long and suffer some level of setback.
If I had to give a ball park guess, I would guess Adrian Peterson will be out for two to four weeks. The problem is that an NFL running back won’t be able to avoid forceful bending, which means that upon his return, the chances of re-injury are higher than most.
When you consider the elephant in the room that he is a 31-year-old running back, and that productive running back play after 30-years old is rare; my advice is find a strong plan B for Adrian Peterson as this may very well be the beginning of the end.