Orlando Magic forward Jonathan Isaac is expected to miss at least eight weeks secondary to a severe knee sprain and bone bruise.

It all began as a routine fastbreak for Orlando Magic forward Jonathan Isaac. The lanky 6-foot-11 defensive menace out of Florida State gathered a loose ball and attempted to bypass his defender, Bradley Beal of the Washington Wizards, with a Euro-step. Rather than planting safely on the red-painted lane and in a position to allow for Isaac to take flight, his left foot became entwined with Beal’s, hyperextending his knee and causing Isaac to crumple to the ground in a heap. Isaac immediately grabbed his knee, screaming in pain. A few moments later the Magic’s athletic training staff escorted him off the court on a stretcher.

The following afternoon, ESPN’s Adrian Wojnarowski reported that Isaac escaped a torn ACL, but suffered “a severe sprain and bone contusion” of this left knee. John Denton, a contributor for the Magic’s official site, further elucidated the diagnosis, reporting than an MRI revealed “a posterior lateral corner injury and medial bone contusion.” Both reporters stated that Isaac would be re-evaluated in 8-10 weeks.

While Isaac managed to avoid tearing three of the major ligaments of the knee — the ACL, PCL and MCL — a posterior lateral (or posterolateral) corner injury is still significant. The posterolateral corner is comprised of a number of anatomical structures, including the LCL, joint capsule, (the little known) popliteofibular ligament and multiple muscle tendons; it is unknown which anatomical structures Isaac injured based on the current reporting. The purpose of the posterolateral corner is to help stabilize the knee against excessive rotation, hyperextension and varus stress (i.e. bending the knee “out”) forces. Isaac’s injury, unfortunately, had all three elements.

Posterolateral corner injuries, just like any soft tissue injury, are graded on a scale of 1-3, with grade 3 being the most severe. Based on Wojnarowski’s use of the term “severe” as well as the corresponding re-evaluation timeline, it is safe to assume that Isaac’s injury is either of the grade 2 or 3 variety.

Grade 2 and 3 posterolateral corner injuries result in significant instability in the knee and can be treated surgically or conservatively, with most teams and athletes choosing to avoid surgery if at all possible. Much like with the MCL and other so-called “capsular ligaments” (i.e. ligaments that are, essentially, thickenings of the joint capsule), the posterolateral corner is often able to heal without surgical intervention due to its relatively high blood supply. ACL injuries, on the other hand, require surgery because they have little, if any, natural blood flow.

Severe posterolateral corner injuries usually heal within 6-8 weeks if they are able to do so without the need for surgery, hence, the 8-10 week re-evaluation timeframe. If surgical intervention is ultimately required, the athlete may miss between 4-6 months.

What throws an extra wrinkle in regards to Isaac’s injury is the presence of a bone contusion (i.e. bone bruise) located at his medial, or inner, knee. It is fairly common to see concomitant bone bruises opposite to significant ligamentous injuries in the knee; in essence, as one side of the knee is stretched to its breaking point, the opposite side is compressed.

Bone contusions fall on the fracture spectrum and are so-called due to the presence of dark, bruise-like artifacts on the bone when viewed via MRI. The ends of long bones, like the thigh bone (femur) and shine bone (tibia), are comprised of spiderweb-like boney tissue known as trabeculae. When the trabeculae fracture, blood is released and a “bruise” appears on the bone on MRI.

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Every bone bruise seems to heal at its own rate, making stamping down a specific recovery timeline difficult. The main limiter for return to play with regards to bone bruises is often pain tolerance.

Missing Isaac for two months at the minimum has the potential to be a devastating blow for the Magic, who are trying to build on a surprising trip to the playoffs one season ago (Orlando lost to the eventual champion Toronto Raptors in five games in the first round).

Prior to his injury, Jonathan Isaac was playing some of the best basketball of his young career and was a major reason why the Magic currently find themselves as the 8-seed in the Eastern Conference; as of writing, Orlando is 2.5 games ahead of the Charlotte Hornets and Chicago Bulls for the coveted last playoff spot.

Isaac, who is averaging a career-high 12.0 points, 6.9 rebounds and 1.4 assists per game, has been a stalwart on the defensive end of the court. In addition to tallying 2.4 blocks and 1.6 steals per game, Isaac has appeared in four of the Magic’s 10 best lineups (minimum of 20 minutes) when sorted by defensive rating, including two of the top four (these lineups have defensive ratings of 71.4 and 96.2, respectively), according to NBA.com/stats; Orlando has a net rating of 0.3 when Isaac is on the court (only Nikola Vucevic, Michael Carter-Williams and Mohamed Bamba do not have negative “on” net ratings for the Magic) and a minus-4.9 net rating when he is off (second to Vucevic’s minus-5.0 “off” net rating).