Zion Williamson’s right knee lateral meniscus tear: Explaining the surgery & five potential root causes

New Orleans Pelicans #1 draft pick and much anticipated rookie phenom Zion Williamson has been diagnosed with a right knee lateral meniscus tear that required surgical debridement.

In this piece, I’ll explain the injury, the procedure, five potential underlying causes for the injury, and why it’s a serious issue moving forward.

If you prefer video, I’ve got you covered as well:

The injury


The meniscus is a dual-crescent shaped, force absorbing, friction reducing piece of cartilage that sits between the femur (thigh bone) and tibia (shin bone) within the knee joint.

One half sits on the inner (medial) aspect of the knee and the other sits on the outer (lateral) aspect of the knee.

Although many meniscus’s tears don’t require surgery, the Pelicans medical staff decided surgery was the best option moving forward.

The surgery

There are two surgical options for meniscal tears: Removing the damaged cartilage – known as a meniscectomy or debridement – or repairing the damaged cartilage – known as a meniscal repair. Per the Pelicans official statement, Zion had the former.

The repair is only an option when the tear occurs in a part of the meniscus that is vascularized, meaning it has blood supply. Repaired tissue cannot heal without blood flow.

As you move from the outer (peripheral) part of the meniscus to the inner (central) part of the meniscus, there’s less and less and blood supply – schematically represented as red, pink, and white zones.

To that point, meniscus injuries are like real estate – it’s all about location location location. A large bucket handle tear on the periphery of the meniscus would be more amenable to repair than a smaller tear that sits centrally.

Return to play (RTP) timeline

The research shows that the average RTP timeline for elite athletes after a repair is 5.6 months whereas the average RTP after a  debridement is six weeks. In line with that, the Pelicans have given a 6-8 week return timeline for Zion, which conservatively means he’ll be back by mid-December.

Five possible underlying causes

1 – Weight

There’s been considerable talk about Zion’s weight and how that contributed to his injury. Gaining weight – in and of itself – isn’t an issue when it’s done methodically to build lean muscle and a leaner body composition.

However, that didn’t seem to be the case with Zion as he looked noticeably less defined and rotund when he showed up for summer league. 

To that point, his former coach, Coach K, said that Zion shouldn’t have played in the summer league at all because he wasn’t in physical – or mental – game shape. Additionally, new Pelicans GM David Griffin also admitted that Zion wasn’t in good shape, particularly from a cardiovascular conditioning standpoint.

Unfortunately, we’ve seen this before from Zion. During his 2017 summer stint with USA basketball, the very reliable and astute Jonathan Givony and Mike Schmitz noted that Zion looked  “heavy and out of shape”.

Fool me once, shame on you. Fool me twice…

2 – Activity load fluctuations

Additionally, Zion went from multiple months without focusing on his fitness after Duke’s tournament exit in March to playing one game in summer league to then participating in camp and playing in multiple pre-season games, with a Pelicans team that plays at a really high pace and running quantity.

These large jumps in activity are a key risk factor for soft tissue (muscle, cartilage, ligament, tendon, bone) injury and, to that point, one of the main standards of sports performance and injury prevention is a formula called the acute:chronic workload ratio which looks at your current level of activity (acute) compared to your overall level of activity (chronic). When the chronic level of training has either underworked or overworked an athlete relative to their current level, the research shows a 7x increase in soft tissue injuries.

3 – Biomechanical

I’ve been concerned about Zion’s movement patterns and mechanics since I saw him in high school, primarily his landing mechanics.

Studying the film, Zion likes to land on one leg with his knee extended, occasionally on his heel. This is the trifecta of landing injury risk because it creates a huge shock wave of ground reaction force (GRF) upwards, with research showing a force upwards of 7x your bodyweight that is primarily absorbed by the joints because the muscles – the body’s primary shock absorbers – are placed in a very disadvantageous position.

In contrast, landing on the mid-foot with knees flexed (bent) only creates a GRF that’s roughly 3x your body weight with most of the force attenuated by muscles rather than joints.

The cherry on top is the height that Zion gets on his jumps which further serves to significantly increase the force of landing.

The second possible bio-mechanical factor is running mechanics. This is really difficult to tell from game tape alone but the team can do a running gait analysis to check Zion’s typical running stride for stride length and then correct as needed.

Over-striding puts excess stress on the lower body because it typically means you’re striking the ground with your heel with your knee extended which – as we already discussed with landing mechanics – increases ground reaction force (GRF) and stress through the joint.

Thirdly, I’ve seen and heard commentary on the way he walks and how that could be contributing to the knee problem.

Typically, this lateral shift during stance phase can be indicative of weak hip abductors – primarily the gluteus medius – and/or muscle tightness on the outside of the hip, particularly the tensor fascia latae (TFL).

However, I haven’t seen much, if any, of that pattern carry over to the game.

The question becomes is his walking gait pattern more of a neuromuscular habit or can we attribute it to some functional deficit? That’s nearly impossible to answer without further assessment. I will say it’s not uncommon to see players move differently in game than outside of the game or even on similar in-game movements.

For example, Steph Curry displays significant knee valgus on his jumper but that doesn’t translate to other in game jumps or his walking gait.

4 – Risk/reward calculus

Zion is an incredibly high energy, high activity player – which when paired with his elite athleticism and drive, makes him such a unique prospect – but it also leads to him playing with a reckless abandon that too often puts him into high risk situations.

This characteristics remind me of Blake Griffin earlier in his career where he was very liberal with his use of athleticism and explosiveness, leading to a plethora of high risk situations.

To Blake’s credit, he learned his lessons and adjusted his game to understand when to and when not to use that explosiveness. It’s a lesson that Zion will have to master as well.

Further, a key part of Zion’s game is using jarring lateral jump stops and hard pivot rotations. These remind me of a young DRose who relied on heavy, shifting jump stops for acceleration and deceleration along with hard pivots and rotations for change of direction. I’m not saying Zion will share Rose’s injury history but these movements aren’t the easiest on your body, especially when done repeatedly over time.

5 – Compensation

In a period of 6 months, Zion had two insults to his left knee – a grade 1 MCL tear at Duke and knee to knee contact during game 1 of the summer league that kept him out the remainder of the tournament.

It’s certainly plausible that these issues could’ve to Zion favoring that left side and compensating with increased loading on his right leg and knee. Over time and reps, that increased stress – even if slight – can lead to downstream injury.

Overall, there’s a distinct possibility in my opinion that one, some, or all of these factors may have contributed to the lateral meniscus tear and subsequent need for debridement.

Risk moving forward

Lateral meniscus debridements are concerning for elite athletes because they can lead to arthritic changes in the knee in less than five years whereas those changes may not be seen after a medial meniscectomy for upwards of 20 years.

Medial vs lateral differences

That stark contrast is due to anatomical and biomechanical differences between the lateral (outer) and medial (inner) compartments of the knee joint, respectively. The medial knee joint is larger and more stable because the outwardly rounded (convex) femur (thigh bone) sits neatly into the inwardly rounded (concave) tibia (shin bone). This convex-concave bony relationship is akin to a ball sitting into a cup. On the other hand, the lateral side of the knee joint is smaller and less stable because both the femur and tibia are convex (outwardly rounded) – like a ball sitting on another ball – with increased translation (movement) and higher shear forces along that side of the joint.

Lateral meniscal function

Accordingly, the meniscus on the lateral side plays a substantially different role than it does on the medial side. On the smaller, less stable, higher sheer force lateral side, the meniscus serves to help mitigate each of these aspects – providing stability while increasing joint surface area to help distribute and absorb the higher stress of the shear forces.

That’s why removing a piece of the lateral meniscus can lead to potentially devastating changes in the knee. In Zion’s case, we can only hope that the piece of irritated and debrided meniscus is relatively small so as to only mildly disrupt the biology and function of the lateral meniscus and thus reduce the chances and rate of arthritic changes.  

All in all…

All in all, this is a concerning injury for Zion due to the functional importance of the lateral meniscus, the future risk associated with lateral meniscectomies and inherent risks that come with his current playing and movement style. At the least, it’s a serious wake-up call for addressing those potential underlying causes and could prove to be a catalyst in Zion taking a more consistent and long-term approach to his health and fitness.

That’s a wrap for this piece. Thanks for reading. My goal is to provide you with in-depth, evidence based, narrative free analysis and you can always find me on IG and Twitter @3CBPerformance. Make sure to subscribe to the YouTube channel and the blog for the latest updates. 3CB out.

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