Klay Thompson’s ACL Injury

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Yet Another Anterior Cruciate Ligament (ACL) injury took place in the NBA when Golden State Warriors’ Shooting Guard, Klay Thompson landed awkwardly after going up for a layup during the 2019 NBA Finals.

ACL injuries occur with rapid deceleration, hyperextension of the knee, and with rotation of the lower leg. Klay’s injury was non-contact, meaning that upon landing there was no direct contact to the knee causing the injury. 

The ACL is one of the four major ligaments that provide stability to the knee joint.  It prevents anterior translation (forward motion) of the tibia (lower leg bone) on the femur (thigh bone) with a secondary job of resisting rotational forces on an extended leg. 

Thompson suffered a Grade 3 ACL sprain, which is a complete tear. Surgery is usually required for this type of injury, especially if one is looking to return to competitive sports. Klay reportedly underwent a successful ACL surgery on July 2nd. The lag in time between the injury and surgery date was due to the fact that the surgeons wanted to allow swelling in the knee to minimize as that would ensure a better outcome. 

The time table for his return is roughly 8-16 months, with the average return being 1 year.  Harris et al, had done a study in 2013 on 58 NBA players who underwent ACL reconstruction while in the NBA. 98% of the players returned to the NBA next season (11.6 months +/- 4.1 months).  This is usually what we can expect, but athletes like Adrian Peterson (former running back for the Minnesota Vikings) changed that perception when he returned 9 months after tearing his ACL to run for over 2,000 yards and dominate the NFL. 

At 29 years old, Thompson is slightly on the older end of the mean age of the group analzed in the previous study. According to the study, a player’s performance did not significantly decline upon return to play.  However, in the first season back from ACL injury it is common to see a drop in overall performance, but in the season following, players usually return to their pre-injury levels.


Thompson will need at least 6-8 months of rehab before being able to step on the court for a full practice, as there is still an intense recovery process he will have to go through. 

For the first couple of weeks after surgery, Thompson will be wearing a brace until he regains adequate knee extension mobility and strength.  The most important thing in the beginning phase of rehab will be to protect the graft, reduce any swelling/inflammation and to restore full knee extension.  

In the next phase of rehab (weeks 4-10), rehab will be focused on improving range of motion, regaining strength, balance, proprioception (the limbs awareness in space), and gait training to normalize his walking.

Between the 3rd and 4th months of rehab, Thompson will be looking to get his affected leg as strong as possible.  The goal of this stage is to prepare for return to sport activities. In months 4-6, we expect Thompson to return to plyometric exercises, sport-specific drills, as well as continuing to improve mobility, stability and strength. 

After this phase, Thompson will be cleared by team doctors and slowly transition back into basketball.  Once Thompson can return to playing full court 5 on 5 with no setbacks, expect him to make a return to the NBA shortly thereafter.  

Active players in the NBA who have torn their ACL include, Kristaps Porzingis (still recovering), Zach Lavine, Kyle Lowry, Jabari Parker, Derrick Rose, Ricky Rubio, Iman Shumpert, and Danilo Gallinari.  

All have returned to playing in the NBA with varying recovery times. Lowry tore his ACL in college and returned 4 months later to finish the season.  Rose was out for 16 months while Gallinari tried to avoid surgery at first and ultimately took 20 months to return.  

Most players came back from their ACL injuries to play again in the NBA, with mixed results. Also, most players eventually returned to their peak form, if not coming back better than before. For a few players who tore their ACL’s near the end of their careers, it forced them into retirement (Baron Davis, Chris Andersen). 

Given Thompson’s playing style, he should be able to return to form quickly offensively as he usually relies on his shooting touch.  Often taking few, if any dribbles before going up for a shot. Thompson has had games where he scored 43 points with the ball touching the floor 4 times, and 60 points where the ball touched the floor 11 times with a total possession time of 90 seconds. 

He may take a step back defensively upon returning since defense requires a lot of sudden changes of direction and cutting motions to defend the opposing player. With Thompson’s athleticism and defensive prowess, expect Thompson to return from his ACL reconstruction and perform at a high level shortly after returning to the court.  

With Thompson likely undergoing a patellar tendon autograft, which usually provides athletes with the greatest chance of performing at pre-injury levels, expect Klay to be out for at least 8-12 months from his surgery. So the earliest Thompson could be back would be March/April, and if he has a speedy recovery with no setbacks he could make an impact for the Warriors at the end of the season.

He may potentially also be a game-changing player for fantasy playoffs.  However, expect the Warriors to hold Thompson out and give him a full year and offseason to recover unless they are making a deep run in the playoffs.  Expect Thompson to return to his old self by the time he steps on court for the 2020-2021 NBA season.

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