Lakers wing Rui Hachimura left Thursday’s game against the Wolves in the third quarter with an apparent left knee injury he suffered after an innocuous-looking dunk on a fast break.

Rui walked off without a noticeable limp, but you could see him touching around his left kneecap area as he walked down the tunnel towards the home locker room.

In the last few days, head coach JJ Reddick gave further insight on the injury, calling it patellar tendinopathy and revealing he will be re-evaluated in a week.

So what is patellar tendinopathy and how long might Rui be out for? Let’s start with some basic anatomy.

Patellar tendinopathy refers to the patellar tendon, which sits below the kneecap (patella) and connects to the top of the tibia (shin bone).

It’s part of the “extensor mechanism of the knee” which helps straighten the knee. Additionally, it’s involved in controlling the knee when it is flexing (bending). That means it comes under stress during basically all basketball movements, including running, landing, decelerating and jumping.

It’s these repeated motions over time that can lead to overload at the tendon and pathology. Tendinopathy literally means pathology of the tendon.

Jumping and landing in particular loads the patellar tendon, which is why patellar tendinopathy is colloquially referred to as “jumpers knee.” It’s no surprise, then, that Rui felt the issue after going up for a dunk.

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The keys for Rui’s return timeline will depend on how badly he aggravated the tendon and how he responds to treatment.

Based on the aforementioned one-week re-evaluation timeline, this sounds like a relatively mild issue. Still, you have to allow some time for the tendon to calm down out of what’s termed as the “reactive” phase and then gradually start loading it again to see how it responds. This will start with lower load activities and then progress to basketball-specific activities with constant monitoring of how he feels during and after.

Tendons — and therefore tendon rehab — are unique in that they have to absorb force and then release it. That requires elasticity, almost like a spring. This level of demand creates high stress on the tissue, so it makes sense for the Lakers’ medical staff to be methodical with his return to play because you want to get out ahead of the injury rather than constantly be playing catch-up where the tendon is constantly flaring up and causing pain and dysfunction.

All in all, this isn’t an uncommon injury and something many basketball players deal with. After returning, Rui will likely be day-to-day for the foreseeable future. It’s tough timing because he has been playing so well for the Lakers — particularly showing huge strides on the defensive end — but you would rather deal with this now than worry about it down the line and into the playoffs.