BROOKLYN, NY - OCTOBER 23: Kyrie Irving #11 of the Brooklyn Nets looks on against the Minnesota Timberwolves on October 23, 2019 at Barclays Center in Brooklyn, New York. NOTE TO USER: User expressly acknowledges and agrees that, by downloading and or using this Photograph, user is consenting to the terms and conditions of the Getty Images License Agreement. Mandatory Copyright Notice: Copyright 2019 NBAE (Photo by Nathaniel S. Butler/NBAE via Getty Images)

Brooklyn Nets star Kyrie Irving has been battling a shoulder condition known as impingement. What is it and how long will it take to recover?

The Brooklyn Nets announced on Friday that star point guard Kyrie Irving will miss the next three games, extending his total streak to seven, secondary to a diagnosis of impingement in his right shoulder.

ESPN‘s Malika Andrews reports that, “[Nets’ Head Coach Kenny Atkinson] said this week that Irving has yet to participate in practice since tweaking his shoulder. Irving, who is still unable to shoot comfortably, is undergoing daily treatment.”

Irving is currently averaging a career-high 28.5 points per game, but his shoulder injury is likely an explanation for his lackluster shooting, particularly from beyond the 3-point line, to begin the season. When corner 3s and half-court heaves are removed from the sample, the shifty guard is currently shooting 30.2 percent (23-for-76) from deep; he’s shooting 34.1 percent on 8.3 attempts per game overall.

But what, exactly, is shoulder impingement and why would it impact Irving’s ability to shoot?

There are multiple forms of shoulder impingement, but with regards to Irving, there are two main suspects.

The first is known as internal impingement. This condition occurs when the structures in the back of the shoulder — also known as the posterior shoulder — are repeatedly pinched. This is most commonly seen in throwing athletes as the posterior shoulder maximally impinges during end-range external rotation combined with abduction. While it can’t be ruled out, this is unlikely the diagnosis that Irving is suffering from.

The most likely culprit is known as subacromial impingement syndrome, otherwise known as subacromial pain syndrome. Subacromial impingement syndrome is a garbage pail term for a variety of symptoms including pain at the front of the shoulder that doesn’t radiate past the elbow, pain with overhead activities, impaired range of motion, and weak rotator cuff musculature among others.

When the arm is brought overhead in an individual who is diagnosed with subacromial impingement syndrome, the head of the humerus — the ball of the shoulder — migrates upwards in the glenoid cavity — the socket of the shoulder — and pinches the supraspinatus tendon and subacromial bursa; the supraspinatus is one of the four muscles of the rotator cuff. This impingement occurs underneath the acromion, which is where the collar bone and the shoulder blade meet. Frequently, a tendinosis — the more medically correct term for tendinitis — of the supraspinatus accompanies the impingement.

Subacromial impingement syndrome is a very common and painful diagnosis among overhead athletes. The injury is usually caused by repetitive overhead activity, such as shooting a basketball. In essence, the supraspinatus becomes overworked, which causes the nervous system to “shut down” the surrounding muscular tissue in an attempt to protect the injured structures; this is known as inhibition. Additionally, the ligamentous capsule that surrounds and helps stabilize the shoulder joint becomes tight, which increases pain and decreases range of motion. Treatment for subacromial impingement syndrome includes loosening up the joint capsule, applying targeted, controlled loading to the supraspinatus, and attempting to strengthen the other three rotator cuff muscles as well as the muscles that assist with movement of the shoulder complex.

What can make this diagnosis difficult to treat at times is when the supraspinatus truly has a tendinosis. Tendinoses are common amongst athletes, as the injury is caused by chronically impaired loading of the involved tissue; for some athletes, this is overloading of the tissue, whereas with others it’s underloading. Tendinoses can be troublesome injuries to treat as each tends to respond to treatment differently. A true tendinosis occurs when it is confirmed on MRI that minuscule blood vessels and nerves have grown into the tendon; this makes the structure extremely sensitive and painful. Additionally, the fibers of the tendon often become tangled rather than being in parallel as is the case with healthy tissue. So, in order to successfully treat a tendinosis, the blood vessels and nerves need to be removed and the fibers need to be realigned.

As of now, this seems to be best down with targeted, controlled loading of the tendon, which is down with eccentric loading — strengthening the muscle as the muscle lengthens — and/or heavy lifting. This places significant force through the tendon, which appears to help realign the tendon fibers and remove the new vessels and nerves.

In all, it usually takes somewhere between 4-6 weeks for subacromial impingement syndrome to heal, though that doesn’t necessarily mean that the athlete will or needs to sit out that long. The main factor when determining if an athlete is cleared to return to play is pain tolerance. As Andrews reports, Irving isn’t able to tolerate the pain while shooting at this time, so he will miss the next three games. On rare occasion does subacromial impingement syndrome progress to a torn rotator cuff in otherwise healthy athletes.

It is common for subacromial impingement syndrome to recur, but it is rarely a long-term concern. The condition is usually responsive to conservative treatment, though it can take some time, and surgery is rarely, if ever, indicated.

In short, Irving is suffering from a common, though surprisingly complex, shoulder injury that is usually responsive to conservative treatment. Pain tolerance will be the main factor that determines when he is allowed to return to game action, which usually occurs within a month or so.

The Nets are currently 7-8 and sit as the seventh seed in the Eastern Conference after going 3-1 since Irving was sidelined with his injury. Irving will miss games against the New York Knicks, Cleveland Cavaliers and Boston Celtics.