On Sunday, Javonte Williams suffered an injury to his right knee, reportedly tearing his ACL, his LCL, and suffering a nonspecified injury to his posterior lateral corner. In other words, he tore the ligaments stabilizing his knee along the anterior and the lateral posterior. And the bundle of ligaments and tendons at the posterior lateral corner of his knee was also destabilized (this generally means that the tibia and femur can be separated side to side along that posterior lateral axis).
So what do the underlying biomechanics say about this injury and about Javonte Williams’s likelihood of returning to the same pre-injury level of play?
It is important to understand that this injury was very likely set up by repetitive stress/ overdevelopment of Williams’s lateral lumbar areas (specifically below the knee). Although the injury was caused by contact, if you watch the video of the injury, you’ll see that there was nothing unusual about the tackle or the way that Williams hit the ground.
Williams has probably been tackled in a very similar manner a dozen times so far this season, and were it not for an overly-stretched lateral lumbar system, he would’ve absorbed another few dozen such tackles over the course of the season.
So why did a routine tackle cause such a significant injury?
Javonte Williams is medial centric posterior dominant, and fully efficient in his favored medial lumbar areas. This means that Williams’s main ‘engine’, the areas that contribute most meaningfully and efficiently to his running, are along the insides of the backs of his legs. These muscles as a collective mostly drive straight ahead, and Williams is indeed extremely powerful and efficient going straight ahead.
However, in a Shanahan-tree wide zone scheme, the running back very often begins the play running parallel to the line of scrimmage, before cutting/ bursting sideways through a gap in the defense. In other words, Denver’s scheme demands that Williams make powerful sudden changes of direction after running horizontally towards the sideline. These sorts of sudden sideways cuts are largely driven by the lateral lumbar areas, both anterior and posterior. It’s the difference between powering off your big toe (which drives you straight ahead) versus powering off your pinky toe (which drives you sideways). Going straight ahead is largely utilizing medial areas, while going sideways is largely utilizing lateral ones.
In order to play this scheme at a high level, Williams rebuilt his body this past offseason to better accommodate these sorts of powerful sudden changes of direction. Specifically he over-developed his lateral areas below the knee to help drive these changes of direction. If you watch the tape you’ll see very tight, highly involved lateral shins/ calves driving Williams’s cuts.
Unfortunately, by driving these sort of gross whole-body movements from such small muscle groups (the shins/ calves), Williams was putting far too much stress on his lateral knees. Likely leading to stretched, weakened ligaments and tendons. Williams is not naturally very efficient in these lateral areas, and so in utilizing an unsustainable mechanic he caused the tissues to weaken and eventually rupture on contact.
The good news however is that Williams’s main areas of efficiency– his medial posterior lumbar areas– were not reportedly damaged. That Williams’s main ‘engine’ was more or less left untouched amidst the wreckage. This means that Williams is far more likely than most to recover from this injury, to something approximating his pre-injury level of play. He will likely be even more of a straight-line runner upon his return than he was pre-injury, but his ability to power forward and break tackles while maintaining balance/ equilibrium will likely return more or less fully.
A glance at similar catastrophic injuries to recent RBs shows this pattern very clearly. That when an injury/ rupture occurs to an area of greatest use/ efficiency, the recovery is likely to be very slow and incomplete. But that when an injury occurs to a runner who is fully efficient in an undamaged area, even a truly catastrophic injury can be overcome, due to the remaining fully efficient ‘engine’ remaining intact.
Examples of the former include Cam Akers and Marlon Mack (both posterior dominant) who ruptured their Achilles tendons (which is part of the posterior lumbar system), and have yet to come close to approximating their pre-injury levels of play. Whereas James Robinson has already made a very effective comeback from the same type of injury (ruptured Achilles) due to his fully efficient lumbar area being his lateral anterior. So that even though Robinson’s posterior leg drive on his injured leg is noticeably lessened post-injury, it is only of minor consequence to his playing ability due to his main ‘engine’ being on the other side of his leg (anterior).
When he returns, Williams will likely struggle with abrupt changes of direction. But his characteristic straight ahead power and balance will likely return undiminished. Which means that Williams may struggle on his return to fit a Shanahan-tree wide zone scheme requiring sudden powerful cuts. But in terms of raw ability and effectiveness in his preferred straight ahead style, Williams will likely make a full comeback.