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Injury analysis: Making sense of Juan Thornhill’s ACL tear and a potential timetable for return

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Our in-house injury expert, Aaron Borgmann, weighs in on the safety’s injury that will cost him the playoffs.

Kansas City Chiefs v Detroit Lions Photo by Rey Del Rio/Getty Images

We have all heard by now that rookie safety Juan Thornhill did indeed tear his ACL in the Kansas City Chiefs’ last game on Sunday against the Los Angeles Chargers.

Unfortunately, we knew this almost immediately by what we saw in real time watching the game and only had to wait for confirmation in the following days. Now that the confirmation is there, let’s take a look at the actual play and ensuing on-field evaluation to talk about what some people may not have picked up.

With some help from defensive film analyst Craig Stout and his handy video work, we can have a better understanding of how this happened. We rarely get this much video information, so I thought this could be a good way to break it down:

While the injury happens quickly and we cannot see much, it is enough to see Thornhill’s left leg plant at the 19-yard line and shift. I’ve broken the video down into segments that we can see and talk about.

The sideline view actually provides the best shot for the actual injury moment. This is just prior to him planting the left foot.

Left foot in the ground shifting, most likely forward and inward.

The damage is likely done at this point, and we’ll get a better view coming up. His knee is flexed here and moving inward, suggesting the possibility of MCL involvement as well.

The reverse angle shows his leg at the moment of injury (most likely). The knee is in a semi flexed position again, moving inward toward the midline of his body.

Reverse angle of what is most likely post-injury or very close.

Moving on to on-field testing, we see a physician expertly assessing his ACL laxity. Watching the video in real-time will give you an idea of what a lax (either partially or completely ruptured) ACL looks and feels like. If you have ever felt one that isn’t there, you know it versus one that is.

We see an anterior force being applied to the tibia on the femur here to assess for stability.

Seen here is an MCL test to assess for joint laxity in the medial direction. Done by applying pressure to outside of the leg while using the lower hand to take the leg in opposite direction, feeling for a gapping sensation along inside of the knee. The force here is in the direction of the viewpoint of the picture.

All in all, this was a very good clinical example of knee stability testing immediately post-injury. The Chiefs medical staff did an excellent job here.

Thornhill’s potential timetable

While we will never know the exact extent of damage, which is what influences timeline more than anything, the most common timeline for return to play for a standard ACL rupture without complications in rehab is approximately nine months.

However, there are outliers in everything. Some players come back sooner; some come back slower. I always remind the athlete that they are ready when they are ready. In actuality, it is a very individualized process. Standardized timelines are used but are often (in my experience) just guidelines and very seldom ever used as a hard and fast rule.

If a player has the physical ability to play earlier and passes all return-to-play testing, then they do so. If not, they wait until they can.

Complicating factors in this injury, as we have stated, would include meniscal involvement (repair vs. meniscectomy), the need to repair the MCL due to the amount of damage as opposed to letting it scar down and any bone/chondral issues that are more significant than a bone bruise. Should any of these be present, it can extend the person’s individual timeline.

If this is an isolated ACL injury, which we don’t know, I would expect this player to have surgery within a couple of weeks, perhaps even already. Should rehab go without complication, then this athlete stands a good chance to be ready for the regular season, perhaps even participate in preseason games. If not, he will be an excellent candidate for PUP (physically unable to perform) list to protect himself further and advance his rehab.


Aaron Borgmann is the founder of Borgmann Rehab Solutions. He spent 12 years in the NFL as an assistant athletic trainer and physical therapist before joining Arrowhead Pride.