Does ACL Surgery Really Prevent Arthritis?

Almost every patient asks some version of the same question after an ACL tear: "In the long run, doctor, which is better for my knee — surgery or no surgery?"

It's a fair question, and it deserves an honest answer rather than a reassuring one. Before we can even compare the two options, we need to agree on what "better" means. Function, confidence, return to sport, and quality of life all matter — but the most objective long-term yardstick is the rate of knee osteoarthritis (OA), because it can actually be measured on an X-ray years later, independent of how a patient feels on any given day.

So here is the real question patients are asking: does ACL reconstruction reduce the risk of future arthritis compared with non-surgical treatment?

The honest answer is: it's genuinely not clear, and any surgeon who tells you with certainty that surgery will protect your knee from arthritis is overstating the evidence.

Why the injured knee is never quite the same again

Whether or not you have surgery, the moment your ACL tears is the moment the clock starts. The injury is rarely just a torn ligament — it typically involves a bone bruise where the femur and tibia briefly impact each other, and this bone bruising has been linked to more severe, longer-lasting joint damage.¹ Even when the cartilage looks structurally normal on imaging afterward, it has already been through a biochemical stress event: the trauma triggers inflammatory mediators in the joint fluid that can degrade cartilage matrix over time.¹

This is why, as I tell my patients, the injured knee will almost certainly develop earlier arthritis than the other knee — regardless of whether you choose surgery or not. The index injury itself is the first hit. What happens after that first hit is where surgery and non-surgery genuinely diverge, and where the real controversy lies.

What the research actually shows — and why it conflicts

This is the part I want to be transparent about: the studies do not agree with each other, and some point in opposite directions.

Some large meta-analyses suggest surgery is associated with more arthritis, not less. A 2023 meta-analysis of three randomised controlled trials found the relative risk of knee OA was higher after ACL reconstruction than after non-surgical treatment.² A separate systematic review and meta-analysis of studies with at least 10 years of follow-up reached a similar conclusion — a higher risk of radiographic knee OA in the surgical group, although paired with a lower risk of needing secondary meniscal surgery.³

Other high-quality studies show no difference at all. The largest and most rigorous meta-analysis on this question to date — led by my mentor, Professor Stefano Zaffagnini at the Rizzoli Orthopaedic Institute in Bologna, — pooled 12 comparative studies and over 1,000 patients and found no significant difference in the rate of knee OA between surgical and non-surgical treatment.¹ Interestingly, the researchers had actually hypothesised going in that surgery would show a protective effect on arthritis — and their own data did not support that hypothesis. What surgery did show a clear advantage in was better objective knee function and a significantly lower rate of secondary meniscectomy.¹

This "no difference in OA, but fewer meniscus removals" pattern shows up repeatedly. The five-year KANON randomised trial found no significant difference in radiological OA, patient-reported outcomes, or meniscal surgery rates between early reconstruction, delayed reconstruction, and rehabilitation-first management.⁴,⁵ The Delaware-Oslo cohort study, comparing surgical and non-surgical treatment in patients who underwent structured rehabilitation first, found comparable knee function and sports participation between groups.⁶ A 10-year matched-pair study of high-level athletes found no statistical difference in OA or meniscal lesions between operative and non-operative treatment, although the operated knees were more stable.⁷ When that same cohort was followed for 20 years, the result held: no significant difference in OA, function, or meniscectomy rates between the two groups.⁸ And a 5-year US cohort study in which both groups underwent identical criterion-based rehabilitation found no difference in radiographic OA or functional outcomes, concluding that favourable outcomes are achievable with either approach.⁹

And at least one older systematic review found the opposite of both — a slightly higher rate of radiological OA in the non-operative group at 17-to-20-year follow-up, though this remains a single, older outlier in the literature.⁸

So: some studies say surgery is worse for arthritis, most say there's no difference, and a minority say surgery is better. This is precisely the kind of conflicting picture I want my patients to see with their own eyes, because it explains why I refuse to give a falsely confident answer.

The variable that actually seems to matter: repeated pivoting

If the studies disagree so consistently, something else must be driving the outcome that isn't simply "surgery" versus "no surgery." The most convincing explanation, and the one I discuss with my own patients, is this: it isn't the reconstruction itself that protects the joint — it's whether you can avoid repeated pivoting and giving-way episodes afterward.

Here's the biological logic. Every time an ACL-deficient knee pivots or gives way, the meniscus and articular cartilage absorb another episode of abnormal shear and rotational load. Meniscal injury is one of the most consistently identified risk factors for later knee OA across this entire body of literature.¹ ³ ¹⁰ An unstable knee that keeps buckling during pivoting sport is a knee that keeps re-injuring its meniscus — and it's the accumulating meniscal damage, not the absent ligament per se, that appears to drive long-term joint degeneration.

This is exactly why the studies split into two camps:

• When non-surgical patients successfully avoid pivoting — through lifestyle modification, activity changes, or, as some data suggests, when they are good functional "copers" — they can do just as well as surgical patients, because they've removed the repeated-injury mechanism entirely.⁶ ⁹
• When non-surgical patients cannot avoid pivoting — because they return to cutting, pivoting, or contact sport without adequate dynamic stability — they accumulate recurrent instability episodes and secondary meniscal tears at a much higher rate. One recent 2-year cohort comparing surgical stabilisation against a structured non-operative bracing protocol found a striking difference in this exact mechanism: a 70% rate of recurrent instability and a 62% rate of medial meniscal tears in the non-surgical group, compared with 2.5% for both in the surgical group.¹¹

Surgery's real value, in other words, may not be a direct "anti-arthritis" effect of the graft itself. It's that a well-reconstructed, stable knee is far less likely to keep pivoting and re-injuring the meniscus during sport — and that mechanical protection against recurrent injury is what ultimately protects the cartilage over decades.

So what should you tell a patient?

Not this: "Surgery will reduce your risk of arthritis." The evidence simply doesn't support that as a blanket statement, and in some studies it points the other way entirely.

Instead, this is the honest, nuanced framework I use:

1. The injury itself has already changed your knee. Whatever you choose, this knee is statistically more likely to develop earlier arthritis than your uninjured knee.
2. What happens next matters more than which treatment you pick. If you can reliably avoid pivoting, cutting, and giving-way episodes — whether through surgical stability or through disciplined activity modification — your arthritis risk tends to plateau rather than climb.
3. If you cannot avoid pivoting without surgery, reconstruction is there to give your knee the mechanical stability to prevent those repeated episodes — recognising that surgery does not guarantee you will avoid every future pivoting or re-injury event, especially with return to high-demand sport.
4. We cannot promise the future. No study can tell an individual patient in advance whether they will be a successful "coper" without surgery, or whether a reconstructed knee will hold up perfectly through years of competitive sport.

Both paths — surgery or no surgery — are genuinely viable options for reducing long-term arthritis risk, provided the real goal is kept in view: minimising recurrent pivoting episodes on the knee, by whichever route gets you there most reliably for your body, your sport, and your life.

I believe part of good surgical practice is having the humility to say "we do not fully know" when the evidence is this evenly balanced — rather than manufacturing false certainty to make a decision feel easier than it is. I've always found it fitting that a joint as intricately and purposefully designed as the knee resists such simple, one-line answers; a structure engineered with this much precision deserves a decision-making process with the same level of care.

References

1. Cuzzolin M, Previtali D, Zaffagnini S, Deabate L, Candrian C, Filardo G. Anterior Cruciate Ligament Reconstruction versus Nonoperative Treatment: Better Function and Less Secondary Meniscectomies But No Difference in Knee Osteoarthritis—A Meta-Analysis. Cartilage. 2021;13(Suppl 1):1658S-1670S.
2. Ferrero S, Louvois M, Barnetche T, Breuil V, Roux C. Impact of anterior cruciate ligament surgery on the development of knee osteoarthritis: A systematic literature review and meta-analysis comparing non-surgical and surgical treatments. Osteoarthritis Cartilage Open. 2023;5(3):100366.
3. Lien-Iversen T, Morgan DB, Jensen C, Risberg MA, Engebretsen L, Viberg B. Does surgery reduce knee osteoarthritis, meniscal injury and subsequent complications compared with non-surgery after ACL rupture with at least 10 years follow-up? A systematic review and meta-analysis. Br J Sports Med. 2020;54:592-598.
4. Frobell RB, Roos EM, Roos HP, Ranstam J, Lohmander LS. A randomized trial of treatment for acute anterior cruciate ligament tears. N Engl J Med. 2010;363(4):331-342.
5. Frobell RB, Roos HP, Roos EM, Roemer FW, Ranstam J, Lohmander LS. Treatment for acute anterior cruciate ligament tear: five year outcome of randomised trial. BMJ. 2013;346:f232.
6. Grindem H, Eitzen I, Engebretsen L, Snyder-Mackler L, Risberg MA. Nonsurgical or surgical treatment of ACL injuries: knee function, sports participation, and knee reinjury: the Delaware-Oslo ACL cohort study. J Bone Joint Surg Am. 2014;96(15):1233-1241.
7. Meuffels DE, Favejee MM, Vissers MM, Heijboer MP, Reijman M, Verhaar JA. Ten year follow-up study comparing conservative versus operative treatment of anterior cruciate ligament ruptures. A matched-pair analysis of high level athletes. Br J Sports Med. 2009;43(5):347-351.
8. van Yperen DT, Reijman M, van Es EM, Bierma-Zeinstra SMA, Meuffels DE. Twenty-Year Follow-up Study Comparing Operative Versus Nonoperative Treatment of Anterior Cruciate Ligament Ruptures in High-Level Athletes. Am J Sports Med. 2018;46(5):1129-1136.
9. Wellsandt E, Failla MJ, Axe MJ, Snyder-Mackler L. Does Anterior Cruciate Ligament Reconstruction Improve Functional and Radiographic Outcomes Over Nonoperative Management 5 Years After Injury? Am J Sports Med. 2018. doi:10.1177/0363546518782698
10. Chalmers PN, Mall NA, Moric M, Sherman SL, Paletta GP, Cole BJ, Bach BR Jr. Does ACL reconstruction alter natural history? A systematic literature review of long-term outcomes. J Bone Joint Surg Am. 2014;96(4):292-300.
11. Porter MD, Shadbolt B. Cross Bracing Protocol for Anterior Cruciate Ligament (ACL) Rupture Has Unacceptably High Failure Rate Relative to Surgical Stabilization: A 2-year Controlled Cohort Study. Clin J Sport Med. 2026.