If You Skip ACL Surgery, What Happens to Your Knee 10 Years Later?
A new review followed knees without an ACL for about 11 years. What it shows about arthritis with and without reconstruction, and why the meniscus matters most.
I recently saw a patient who hurt her knee playing basketball 2 years ago. She felt a pop and had swelling, but the injury soon settled down and she was able to return to basketball. Now, 2 years later, she is having popping and locking in the knee, and an MRI showed that she had an ACL tear all along. Obviously this was a surprise to the patient and her family, but it is something I see regularly. The unfortunate reality is that she now has a bad meniscus tear, likely because the knee was unstable for two years, and it probably would have been avoided with an early ACL reconstruction. So an important question is raised: "Do you need the ACL fixed?"
The honest answer is more nuanced than either side of the debate usually admits. A new systematic review in the American Journal of Sports Medicine looked at what happens, over about a decade, to knees whose ACL was never reconstructed1. The results are worth understanding before you decide.
What the study looked at
The authors pooled 19 studies, including 11 matched cohorts that compared knees without an ACL to knees that had reconstruction. In all, there were 1,432 patients, mostly in their twenties and thirties, followed for an average of 11 years after injury. The outcome was arthritis on X-ray, and the authors counted a knee as arthritic once it reached the mild stage (Kellgren-Lawrence grade 2) or worse.
This is not the same as pain or function. X-ray arthritis and how a knee feels do not always match. But it tells us something real about what is happening to the joint.
What the numbers say, and what they don't
Two things stand out. First, reconstruction did not prevent arthritis. About a third of knees in both groups had some arthritis on X-ray at roughly 11 years, compared with 5.0% in the uninjured knees on the other side. The authors put it plainly: the ACL injury itself is the strongest factor, regardless of treatment. Activity level did not change this in the studies that looked.
Second, the more advanced arthritis was somewhat more common in knees without a reconstruction: 18.1% versus 12.8%. That sounds meaningful, but when the studies were pooled statistically the difference did not reach significance (odds ratio 0.46, 95% range 0.20 to 1.05). I read it as a signal, not a proof, and the studies were mostly observational, so patients who chose surgery may differ from those who did not. Arthritis also climbed noticeably after the 10-year mark, so a knee that looks fine at year five is not necessarily out of the woods.
| Finding | No reconstruction | Reconstruction |
|---|---|---|
| Any X-ray arthritis | 37.8% | 35.2% |
| Moderate-to-severe arthritis | 18.1% | 12.8% |
The meniscus matters more than most people realize
The clearest pattern was that removing meniscus tissue (meniscectomy) went along with worse arthritis in knees without an ACL. It was a strong predictor in 8 of 10 studies that looked. A knee that keeps shifting can tear the meniscus again and again, and each cleanup takes away more cushion. The authors could not test whether meniscectomy explains the gap in moderate-to-severe arthritis, so that question is still open.
This is a big reason I think about the meniscus and the ACL together. Repairing a meniscus, when it is repairable, preserves cushion, and a stable knee gives that repair a better chance of lasting. The authors also point out that longer delays before surgery are linked to more meniscus and cartilage damage.
Who I talk to about this
If you cut, pivot, or jump, or your knee gives way during ordinary life, reconstruction is usually the better path, particularly with a repairable meniscus tear. If you are older or less active, feel stable, and do not play pivoting sports, a structured rehab program is a reasonable choice, and some people do very well with it. Whichever route you take, protecting the meniscus is the part I would not compromise on.
Neither path guarantees you will avoid arthritis. What I can tell you is how each option changes your odds and your day-to-day confidence in the knee, and we can look at your MRI and your goals together.
Frequently asked questions
Does ACL surgery prevent arthritis?
Not by itself. In this review, arthritis was common in both groups. Surgery may lower the chance of the more advanced kind, but it does not eliminate the risk.
Can I skip surgery and do rehab only?
Some people can, especially if they are less active, feel stable, and avoid pivoting sports. If your knee gives way or you want to return to cutting sports, surgery is usually the more reliable route.
Does it matter if I wait?
Waiting is fine while you work on motion and strength, but repeated giving-way episodes can damage the meniscus and cartilage. If the knee is unstable, I would not wait for years.
Is a brace enough?
A brace can add confidence, but it does not restore the ligament or reliably control rotational instability in high-demand sports.
If you have torn your ACL, or you tore it years ago and never had it fixed, I am happy to go through your imaging and your goals with you in clinic. There is rarely one right answer, and the best plan is the one that fits how you live.
References
- Shah A, Gumarathas K, Marks P, Marx RG, Kiss A, Wasserstein D. The long-term radiographic fate of the chronically ACL-deficient knee: a systematic review and meta-analysis of matched cohort studies. Am J Sports Med. 2026;54(8):2021-2029. doi:10.1177/03635465251405438. PMID 41572905
This article is general education, not medical advice for your situation. Every knee and hip is different — talk with your own doctor about your care.