On Monday, Sept. 4, 2017, Minnesota Vikings quarterback Sam Bradford threw for 346 yards and three touchdowns against the New Orleans Saints on national television. It was a magnificent showing and a great continuation of Bradford’s career year in 2016, in which he completed 71.6 percent of his passes and threw for nearly 4,000 yards. Bradford’s aerial assault had Vikings fans excited for the coming weeks and months with hopes of competing for an NFC North title.
However, a week later, after a loss to the Pittsburgh Steelers, a game in which he did not appear, it was revealed that Bradford suffered a mysterious left knee injury, the same knee that had undergone anterior cruciate ligament (ACL) reconstruction twice before.
At the time, Vikings head coach Mike Zimmer stated, “Sam’s fine. He might play one game from now; he might play six weeks from now. Either way, he’s fine.”
Many began to worry if Bradford had suffered a potentially season-ending knee injury; however, these fears were quelled to an extent when it was revealed he had only suffered a bone bruise. This diagnosis was confirmed Sunday morning after Bradford sought a second opinion by renowned orthopedic surgeon Dr. James Andrews. Bradford sat out Sunday’s game against the Tampa Bay Buccaneers as he continues to heal.
But what exactly is a bone bruise? How is it caused? What’s the typical recovery timeline? Will it be an issue all season? These are important questions to ask and I hope the information below sheds a little light onto the situation.
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Though the name doesn’t imply it, a bone bruise is actually a sub-category of fracture. Instead of the outside of the bone (the cortex) splintering apart like in a stress or acute fracture, in a bone bruise, some of the small spider web-like fibers of the so-called “spongy” bone (trabecular bone) at the ends of long bones (like the femur or humerus) crack.
These minuscule breaks result in the rupture of the small blood vessels present in the bone, causing the bone to “bruise” and become tender. This breaking of blood vessels is essentially the same process as the formation of bruises on the skin or in muscle, hence the name.
What makes bone bruises somewhat tricky to diagnosis at first is due to the fact that they are invisible on X-ray images and therefore require magnetic resonance imaging (MRI) to be picked up. X-ray imaging is typically the first imaging modality used when attempting to find a diagnosis, which may delay the revelation of the bone bruise diagnosis for a small amount of time.
It’s been estimated that bone bruises occur in as many as 80 percent of all ACL tears
Bone bruises could theoretically occur in nearly any bone in the body, but with regards to the knee specifically, they most often occur in combination with another injury, especially one that is traumatic in nature. Their mechanism of injury is typically a combination of an axial loading (a force placed directly down the middle of the bone) and twisting with or without a valgus/varus stress (“bending” the knee towards or away from the body’s midline, movements that don’t typically occur to a great extent in the knee).
It’s been estimated that bone bruises occur in as many as 80 percent of all ACL tears and they’re often found in medial collateral ligament (MCL) sprains as well as meniscus tears.
Bone bruises can also occur in the knee as a result of chronic, repetitive stress, similar to a stress fracture, especially if the meniscus, which provides cushion in the knee and prevents the tibia (shin bone) and femur from rubbing on each other, has been damaged or removed. Damage, such as a bone bruise or osteophyte formation (an overgrowth of the bone, which is one of the common indicators of arthritis), may occur over time if the two bones grind on each other due to the of the meniscus.
It’s unknown if Bradford suffered any meniscal damage with either of his ACL tears, but since meniscal tears are extremely common with ACL and other major knee ligament injuries, it certainly wouldn’t be out of the question (Important note: THIS IS JUST CONJECTURE). If, I repeat, IF this is the case, it’s possible that Bradford could struggle with further flare-ups in his left knee in the future.
Like stress fractures and acute fractures, the best antidote for a bone bruise is time. It can take weeks or even months to fully recover from a bone bruise and in an ideal world. Bradford would be given the time to heal. However, the main determinant for returning to play with bone bruises is pain tolerance. Although not allowing the bone to heal fully increases the risk for further injury, if Bradford can tolerate the pain well enough for it not to affect his play or movement, he’ll be healthy enough to return. In that sense, Zimmer wasn’t lying. He could play next week. He could play six weeks from now. It’ll all just depend on how Bradford tolerates the pain. At any rate, this shouldn’t be a season-ending injury, barring something catastrophic occurring.
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