How Close Was Stephen Curry to Tearing His ACL?

This past Sunday, reigning NBA champion and MVP Stephen Curry slipped on the court during Game 4 of the Warriors' first round series and took an awkward fall. While not the most gruesome-looking of injuries, Curry's right knee definitely looked like it hurt:

An MRI later revealed a Grade I MCL sprain of his right knee. The MCL stands for "medial collateral ligament", which is a band of fibrous connective tissue on the inner part of the knee. Its primary job is to limit excessive motion that is directed inwardly at the knee joint. Curry is expected to miss at least two weeks due to this injury, but thankfully it doesn't appear that his ACL (anterior cruciate ligament) was torn--an injury that would require surgery and 9+ months of rehab. 

Two weeks of missed play is extremely costly in the playoffs, especially from the best player in the league on the most victorious regular season team in NBA history. He'll miss the rest of the series against the Rockets which is probably no big deal, but his presence will be missed more against the Clippers (who also have their fair share of injuries with Chris Paul suffering a Boxer's fracture in his right hand and Blake Griffin's right knee pain resurfacing). 

But how close was Curry to tearing his ACL or suffering another tragic season-ending knee surgery in his fall, when he did his best impression of Bambi ice skating?

Let's take a look and analyze his fall. At 0:29 when he first slips, you see that his left leg slides first and he appears to catch his balance with his right leg. The right knee buckles inwardly, thus stressing that MCL, but you'll notice that his knee is quite flexed (or bent) as this occurs. When the knee is in flexion, due to its anatomy the MCL is relatively slackened. It's not taut. And there's a harder chance for ligaments to REALLY tear when they're on slack--probably why it was a Grade I tear and not the more severe Grade III tear (which would require surgery).

So probably not that surprising that it was only a Grade I tear due to how much the knee was bent. How about the ACL on the right leg? The ACL's main job is to prevent excessive hyperextension at the knee, and it does a bunch of other stuff but it actually only has a small role in preventing inward/outward directed forces at the knee. One of the more common ways athletes injure their ACLs is when they take a fall or hit to an extended knee when the foot is planted. Which is not really what you see here in Curry's fall.

At least not in the right leg.

Rewatch the video starting at 0:29 again and take a look at the left leg, the one that he first slips. Curry attempted to catch his balance with his right leg and shifted his weight towards the right, which ultimately led to him injuring that MCL. But had he kept his momentum and continued to fall towards his left leg with the knee extended and his body weight collapsing inwards, there's a possibility he could have torn his left ACL.

A valgus or inwardly directed force at the knee when it is extended can lead to an ACL tear.

A valgus or inwardly directed force at the knee when it is extended can lead to an ACL tear.

Curry attempted to catch his balance with his right leg and shifted his weight towards the right, which ultimately led to him injuring that MCL. But had he kept his momentum and continued to fall towards his left leg with the knee extended and his body weight collapsing inwards, there’s a possibility he could have torn his left ACL.”

It sucks that the floor was wet and that Curry slipped and fell, leading to a two week absence. But there are so many other worse scenarios that could have played out. A left ACL tear and season-ending surgery would surely be an even more devastating blow to the NBA's poster child and to the Warriors' incredible season. I think he's one lucky guy, and he'll be back in top shooting form when he returns as he will likely have some of the best physical therapy care the world can offer. 

2016 will end in with a repeat showdown between the Cavs and Warriors; Warriors in 6.