Leave the Shoes At the Door: What’s Really Up with Zion’s Knee?
Understanding knee sprains and uncovering what “day to day” really means for the Duke star
The basketball universe held its collective breath last Wednesday night when Zion Williamson went down at the 19:30 mark of the 1st half of the battle for Tobacco Road. Having his left foot explode through the outer edge of his Nike 2.5 PG while attempting a spin move back to his right resulted in an awkward tumble to the ground that led to his exit from the most anticipated match-up of the college basketball season. News came out Thursday afternoon confirming that the projected №1 pick in the upcoming NBA draft is “day-to-day” after being diagnosed with a Grade 1 Knee Sprain. While this certainly sounds like good news for Zion’s professional future and for this Duke team’s national championship aspirations, knee sprains are a nebulous category of injury that encompasses a wide range of potential severities. When former Carolina Panthers wide receiver Kelvin Benjamin went down on a non-contact injury during training camp in 2015, the initial word from head coach Ron Rivera was that he had also suffered a knee-sprain. Despite the seemingly benign assessment, a follow-up MRI confirmed a torn ACL that kept him out for the year. There’s clearly a lot to sort through when it comes to these types of injuries.
The recent debate surrounding the NCAA and its stringent control over its player’s economic autonomy have led many to question whether Zion should suit up for Duke even if he were to fully recover. My goal in this article is to steer the discussion back towards the injury itself by navigating through the classification of knee sprains and to project what this means for Zion’s recovery timeline based on anatomy, video analysis, and clinical studies.
Knee Anatomy
The knee is the largest joint in the human body and connects the upper portion of the leg to the lower half. Bones, muscles, tendons, and ligaments join at the knee to enable movement. Muscles, which are responsible for generating force, are connected to bone by tendons (composed of connective tissue). When muscles contract they shorten in length — as a result tendons “pull” on the bones, triggering movement.
Important muscles include the quadriceps (front of the leg) and the hamstrings (back of the leg). These overlie and attach to the major bones of the leg — the femur (thigh bone), patella (kneecap), tibia (shin bone), and fibula. Remember that tendons establish the connection between the muscles and bones. The two major tendons in the knee work together to trigger movement. The quadriceps tendon connects the quadriceps (muscle) to the patella (bone), and the patellar tendon connects the patella to the tibia. Thus the patella serves as the middle-man between the upper and lower legs.
But wait, didn’t I say earlier that a tendon connects bones to muscles? And didn’t you just say that the patellar tendon connects the patella (a bone) to the tibia (another bone)? Yes, the naming system is misleading, but it’s easiest to think of the two tendons as working together as a single unit, with the goal of extending the lower leg. In that sense, the quadriceps muscle works to tug on the tibia through the combined action of the two tendons. When we want to extend our lower leg, such as when getting up out of a chair, we contract our quadriceps muscles. This then pulls on the quadriceps tendon, which pulls on the patella and the patellar tendon. Since the patellar tendon is connected to the tibia, the end function is that the tibia (a lower leg bone) is pulled upward.
The final piece of the puzzle that we have to talk about is the ligaments. Unlike tendons, which connect muscle to bone, ligaments connect bones to other bones. Their purpose is to stabilize the knee joint. Anyone who follows sports is familiar with the ACL (Anterior Cruciate Ligament) and MCL (Medial Cruciate Ligament), as these are relatively common injuries that are notorious for having extensive recovery times. In addition to these, there’s also the LCL (Lateral Cruciate Ligament) and PCL (Posterior Cruciate Ligament) — 4 ligaments in total. The word cruciate comes from the Latin adjective “cruciatus”, meaning “cross-like”. In the picture below you can see how the ACL and PCL cross within the joint.
Let’s start by talking about the ligaments that run along the outside of the knee joint. The MCL connects the femur (thigh bone) to the tibia (shin bone) on the “medial” (a.k.a inner) part of your leg — hence the name. So the MCL is the ligament that connects your upper leg bone to a lower leg bone on the inside of your leg, thus preventing the knee from bending too far inward. The LCL connects the femur to the fibula, the lower leg bone that’s located on the more “lateral” (a.k.a. outside) part of your leg. The LCL acts to prevent the knee from bending too far outward. Together these two ligaments stabilize the knee and maintain the alignment of the upper and lower leg bones in the horizontal plane.
The ACL and PCL serve a similar function, with the difference being that they prevent the bones from sliding too far forward or backward. Let’s start off with where the ligaments are located. The word “anterior” means towards the front of your body and “posterior” means towards the back. This helps us to understand that the ACL originates from the front (anterior portion) of the tibia and extends upward and backward to attach to the posterior area of the femur. The PCL attachments are the inverse; they originate from the back (“posterior”) of the tibia and extends upward and forward to insert on the front of the femur. You can see the crossing of these two ligaments in the image below.
So now we can imagine what happens in an ACL injury. Tearing this ligament will sever the connection between the femur and the tibia in the front of our leg — this means that there’s nothing preventing the tibia from moving too far forward relative to the femur. The PCL acts in the same way to prevent the tibia from being displaced too far backward.
Knee Sprain Classifications
Now that we can imagine what’s going on in the knee we can move on with deciphering what Zion’s Grade I knee sprain entails. The most important thing we should clear up is that there’s a difference between a sprain and a strain. A sprain refers to an injury to the ligaments (the stabilizers), while a strain is an injury to the tendons or muscles. Zion suffered from a knee sprain meaning that there’s been an injury to his MCL, LCL, ACL, or PCL. Sprains are classified into 3 categories: grade I, grade II, and grade III.
Grade III: The most severe injury and involves the ligament being completely torn or separated from its attachments to bone. This is the worst possible outcome — Kelvin Benjamin suffered a Grade III ACL injury. As opposed to lesser graded sprains, complete tendon tears may require surgery to reconstruct the severed ligament. Grade III ACL and PCL tears typically require surgery, while Grade III MCL sprains can be treated more conservatively with the RICE(rest, ice, compress, elevate) method. During surgery, the injured tendon is removed from the body and replaced. Surgeons can replace the tendon with a section of tendon from another site in the athlete’s own body, such as the patellar tendon or hamstring tendon, or use a donor tendon from a cadaver (a.k.a. tissue from a dead body).
Grade II: This is a moderate injury and involves a partial tear of the tendon. Unlike grade III this usually does not require surgery. Initial treatment involves wearing a weight-bearing knee brace to avoid stretching the ligament as it heals. Incorporating specific joint exercises and massage can help to accelerate the healing process by guiding the direction of healing that fibers follow.
Grade I: The least severe of all knee sprains where stretching of the ligament causes microscopic tears. Since the integrity of the ligament is kept mostly intact the athlete is still able to support their weight. Similar to a Grade II injury, the best course of action is rest, ice, and anti-inflammatory medications to promote the body’s natural healing process.
Video Analysis: A Frame by Frame Breakdown
So taking what we’ve just learned, let’s take a frame by frame look at the injury suffered by Zion last week.
Here we see Zion prepare to plant on his left foot before spinning back to his right.
Zion’s left foot makes contact with the ground and his shoulders begin to open up to the right. He prepares to explode off the pivot and shift his weight onto his right foot before driving past Maye to the basket.
When Zion’s left foot breaks through the outer edge of his shoe, his entire frame slides out further than his body had anticipated. He had planned to shift all of the weight in his upper body from one foot to the other with his spin move — something his body is perfectly capable of handing when force is distributed throughout the entire leg. However, the unexpected break through his shoe causes him to slide just far enough to prevent the right foot from cleanly planting on the court. His weight falls on the inner edge of the right foot, thus redirecting the weight of his massive frame squarely onto the right knee. Recall that the MCL is the ligament on the inner part of our knee joint. Not being able to make a clean plant directs the bulk of his weight (red arrow) onto the knee joint, with the MCL bearing the most significant burden. This is most likely the ligament that was injured and is responsible for Zion’s knee sprain.
Outlook
So let’s recap everything that we’ve learned. We’ve been told that Zion has been diagnosed with a Grade I knee sprain, meaning that the ligament was stretched but not torn. From the video we can deduce that the injured ligament is the MCL. Due to the mild nature of the injury, the Duke medical staff will use RICE (rest, ice, compression, and elevation) as the primary form of treatment. Within a few days Zion will then begin targeted rehabilitation exercises to strengthen the healing MCL fibers to prevent future injury.
So how long could this injury keep Zion off the court? This 2014 paper published in The American Journal of Sports Medicine studied cadets at the United States Military Academy found that those who suffered a Grade I MCL injury lost a median of 13.5 days to injury. Another paper from 1981 found that football players returned to full athletic participation after an average of 10.6 days following a Grade I MCL sprain. Since treatment for low grade MCL sprains has not changed significantly since the time of the older study, it’s safe to estimate that Zion will be kept off the court for 1.5–2 weeks. With the rematch between these two teams set to take place on March 9th, 17 days will have passed since the injury meaning that basketball fans may finally get to see Zion leave his mark on this historic rivalry.
