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From literature, about 50% of anterior cruciate ligament (ACL) reconstruction patient's are predisposed to osteoarthritis (OA) later in life due to cartilage deterioration and cartilage damage from the injury [Source 1 and source 2]. From my understanding, patient's, if they develop OA, typically only develop it in their injured leg as opposed to the contralateral.

If they are avoiding weight on their injured leg and mainly using their contralateral leg, shouldn't they experience some cartilage deterioration in the contralateral as well due to the gait asymmetry? Is it because they did not have cartilage damage from the injury in that leg?

I am an engineering student studying biomechanics, but I am trying to understand the importance and relationships between ACL reconstruction and development of OA.

While we're here, also the injured leg experiences decreased knee flexion angle after injury. Does this affect cartilage deterioration if you are applying less forces from the flexion?

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    Not my area of knowledge but as an outsider it seems like a great question for this stack. You might improve your question by writing out acronyms (they're fairly clear given context, but still, it's the preferred style here to write them out at first use), and I'd suggest dropping the last question. SE questions are supposed to be single questions; your last paragraph adds an extra one that isn't particularly relevant to the rest. – Bryan Krause Sep 4 '19 at 16:15
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    Good Q. We've had an orthopedic surgeon poke his head in here a couple times so I hope he sees this. We used to have a PT here as well. I will need to dig up some resources for this, but it is a common theme in ortho / sports med that any disruptions in the "kinetic chain" can have effects both ipsilateral and contralateral (as well as proximal and distal) to the injury depending on how the patient changes their movement etc to compensate for the injury. – DoctorWhom Sep 4 '19 at 22:37
  • Can you rephrase the title into a question? Something like "What is the cartilage deterioration rate in patients after ACL reconstruction in contralateral knee?" or "Does the cartilage deteriorate in patients after ACL reconstruction in contralateral knee?" – Bob Ortiz Dec 6 '19 at 11:20
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So there are two aspects to cartilage degeneration after an ACL injury, what they call post-traumatic osteoarthritis (PTOA): the first is the increase in knee laxity after ACL reconstruction and the second are inflammatory molecules within the synovium that surrounds the ACL and cartilage. So while people may overcompensate on their other leg temporarily while they are recovering, there are many causes of OA in the ACL deficient knee that are not present in the contralateral knee.

  1. They have found that all current reconstructive methods, whether it is tendon grafts (for example using the hamstring tendon) or bone-tendon-bone grafts (use of the patellar tendon) do not restore the kinematics of the knee back to baseline. There is joint laxity that occurs due to the improper healing between the graft and the bone tunnels that are created in order to secure the ACL in place. That laxity causes increased load and stress onto the cartilage on the femur and tibia, and, therefore, causing osteoarthritis. https://journals-sagepub-com.ezproxy.med.cornell.edu/doi/10.1177/0363546507307396
  2. There are many pro-inflammatory molecules that are released within the knee capsule after both the initial injury and the reconstruction that have been shown to contribute to the development of OA in the injured knee. In order to not get too in depth, I wont mention all of them, but Tumor necrosis factor-alpha (TNF-alpha) is the one that persisted in the injured knee for years after the ACL reconstruction.The presence of this pro-inflammatory molecule indicates that there is still processes going on that increase the degradation of cartilage through several processes. https://linkinghub.elsevier.com/retrieve/pii/S1063-4584(14)01250-3

So yes, people who undergo ACL reconstruction may have different gaits that cause them to maybe develop OA in the contralateral knee (especially without proper physical therapy) very far down the road, but this probability is smaller than the injured leg due to the factors that I have listed above. That is why the percentage of OA is so much higher in the injured leg than the contralateral leg. My research is in the healing process of ACL reconstruction, so I don't feel entirely qualified to answer that part, hopefully someone else can touch on that aspect of your question! Hope this helped

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