By Abby Sims
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Antonio Cromartie reportedly suffered a hyperextended knee during practice on Thursday, in what was noted to be a non-contact situation. The surprising Jets could suffer on defense without their first-line player, whose status for this weekend is uncertain.
Though an MRI evidently did not reveal significant injury, and no specific diagnoses were made public, Cromartie is clearly not up to speed.
What Is The Significance Of A Hyperextended Knee?
Ligaments — which attach bone to bone — provide stability by restraining excessive movement in our joints. When a joint goes beyond its normal range of motion, the integrity of certain ligaments becomes compromised, resulting in a sprain. In the case of the knee, forceful or traumatic hyperextension into a bowed position stresses the anterior cruciate ligament (ACL) — which is the primary stabilizer of the joint — and may also impact other secondary stabilizers. Worst-case scenario for Cromartie would have been a Grade 3 sprain, otherwise known as an ACL tear. A likely best-case scenario was a Grade 1 sprain, with only mild tweaking of the ligament.
When the knee hyperextends, the tibia (the larger bone in the lower leg) glides forward excessively on the femur (the thigh bone) at the knee joint. This abnormal movement, whether caused by trauma or a non-contact situation, can also result in a bone bruise, or contusion. As with a sprain, the extent of the contusion would be proportional to the degree of hyperextension that occurred and whether trauma played a role. Another factor is the athlete’s baseline — or normal — range of motion.
A prior history of ligament sprain that results in persistent joint laxity predisposes an athlete to excessive joint mobility. This may set the stage for a non-contact injury such as what Cromartie suffered. Many people — particularly ballet dancers and gymnasts — have hypermobile knees, enabling extension beyond a level plane and into a hyperextended position. This expanded range of motion is their “normal”. For a hyperextension injury to occur in these populations, the tibia would have to glide that much further forward, still stressing its restraints.
It is important for an athlete or dancer to have exceptional muscle strength, particularly in those muscles surrounding a less-than-stable joint. It is also vital that strength is optimized at the end-ranges of motion. The hamstrings become particularly vital in the case of the knee, for in their role as knee flexors (in addition to bending the knee, the hamstrings act to extend the hip), they provide a degree of dynamic restraint to limit hyperextension.
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