ACL Surgery and Arthritis Risk Factors

John-Paul Rue, M.D., a Fellowship-trained, Board Certified orthopedic sports medicine surgeon, responded to questions from Healthline.com for a story concerning new research, which identified risk factors for developing arthritis post-ACL (anterior cruciate ligament) surgery.

What is the relationship between arthritis and ACL surgery? Why do people have a higher risk of getting arthritis after this surgery?

The relationship between arthritis and ACL injury, even with subsequent ACL reconstruction is complex. There are clearly many factors involved, including patient-related factors such as age, BMI (body mass index), status of the meniscus and any additional factors such as injury to the cartilage and timing from initial ACL injury to ACL reconstruction surgery to restore stability to the injured knee. Injury to the knee joint such as with an ACL tear, and even the subsequent surgery, can set off a cascade of inflammatory biomarkers which may change the levels of certain compounds in the knee joint and lead to degeneration.

What is your reaction to these findings? How might they help identify and/or improve outcomes in people at risk for arthritis after ACL surgery?

This study does offer some additional insight into why someone might develop progressive arthritis in the patellofemoral (PF) joint after ACL surgery. The author's hypothesis was that altered loading of the PF joint leads to changes in the cartilage of that joint, leading to arthritis. So if someone has had an ACL tear, and had the surgery to reconstruct the ligament, there may be lower PF joint loading forces due to a variety of factors, including movement patterns, stability and even psychological factors. The surprising finding was that lower forces in the PF joint were associated with progression of arthritis, which would seem at first to be contrary to typical thinking that more loading forces on a joint would actually be worse in terms of developing arthritis. Altered mechanics in a knee joint, whether resulting in increased or decreased forces on cartilage appear to be responsible to damage to cartilage. Normal (not higher or lower) forces are required to maintain the healthy homeostasis of joint cartilage health.

What would you say the main takeaway is for readers and why do you suspect less joint loading lowered the risk of arthritis?

Unfortunately, the main takeaway is that arthritis after ACL injury and subsequent surgery, even if that surgery appears to be successful, can still develop over time. While there are many factors involved, monitoring knee loading forces during movements may be an early indicator of who is at higher risk for developing progressive arthritis.

What, in layman's terms, do the authors mean by 'loading' and are there any actionable steps for patients to take? How much weight/force should they put on their knee post-surgery?

Loading generally means how much force or pressure is placed on a joint. For a patient after ACL surgery, the sooner they are able to get back to normal weight-bearing activities and normalize their knee movements, typically the better off they will be.

Are there any other modifiable factors people can take to lower their risk of arthritis after ACL surgery?

One of the keys to limiting the progression of arthritis after ACL injury is to restore the normal stability, functional movement and subsequent normal loading of the knee as soon as possible. Additionally, significant delays from injury to surgery can lead to worsening problems such as meniscal tears, which can increase the risk of arthritis.

Dr. Rue specializes in arthroscopic repair of sports-related injuries, including complex knee and shoulder reconstructions at Sports Medicine at Mercy. He also sees patients at Mercy Personal Physicians at Glen Burnie.