Study: Knee shape predicts which patients do not need reconstruction after ACL rupture

Investigators from Hospital for Special Surgery recently published results that suggest the shape of the knee may impact whether a patient should have their ACL repaired or reconstructed after injury.

“This is the first study to show that after your ACL is ruptured, the changes in the mechanics of the knee can really be affected by the shape of the knee,” Suzanne Maher, PhD, from Hospital for Special Surgery in New York, stated in a press release. “Previously, researchers had only conducted studies looking at whether a particular knee shape makes a person more likely to have an ACL injury, specifically in the athletic population.”

Using a sensor measuring the stresses put on the knee, Maher and colleagues put 9 cadaveric knees through 20 cycles on a machine that replicated walking both before and after cutting the ACL to replicate injury.

Suzanne Maher

“We thought that if we tested all of these knees, we would see consistent changes in contact stresses. We would see some areas of the knee that saw a much higher contact stress than they had before we cut the ACL, and we would see other areas that would see a lower load,” Maher said. “What we found instead was that the change in contact stresses was highly variable. The only consistent finding we had was in the posterior side of the knee; all knees had increased contact stress in the posterior central aspect of the knee, at 45% of the gait cycle.”

Maher said some knees also had increased stress at the front of the tibial plateau in addition to the back, and noted an increased tibial slope was a predictor of increased stress.

“What this study is telling us is there is a particular part of the gait cycle where your ACL is very active,” she said. “It is very active in the latter part of stance phase. When designing an ACL replacement, researchers may want to pay close attention as to what it does in the latter part of the stance phase.”

Reference:

Bedi A. Proc Inst Mech Eng H J Eng Med. 2013;doi:10.1177/0954411913490387.

Disclosure: The study was funded in part by the National Institutes of Health. Maher has no relevant financial disclosures.