If you or someone you care about has just been told there’s an ACL tear, you are likely dealing with pain, confusion, and a pile of medical papers. One of the first things you will see is a strange combination of letters and numbers: the ICD-10 code for ACL tear.
Do not worry. You do not need to be a medical coder to understand this.
In this guide, we will walk you through everything you need to know. We will keep the language simple, the examples clear, and the advice honest. By the end, you will know exactly which code applies to your situation and why it matters for your treatment and insurance.
What Is an ACL Tear? A Quick Overview
The anterior cruciate ligament (ACL) is one of the major ligaments inside your knee. It connects your thigh bone (femur) to your shin bone (tibia). Its main job is to keep your knee stable when you twist, pivot, or change direction quickly.
An ACL tear means this ligament has been stretched too far or completely ripped. It can be:
- Grade 1 (mild): Stretched but still keeps the knee stable.
- Grade 2 (moderate): Partially torn.
- Grade 3 (severe): Completely torn.
Most people with a grade 3 tear feel a “pop” at the moment of injury. The knee often swells within hours, and it may feel like it is going to give way when you try to stand.
Important note: An ACL tear is not the same as a sprain in other ligaments. The ACL does not heal on its own because it has poor blood supply. That is why surgery is often discussed for active individuals.
Why the ICD-10 Code Matters for You
The ICD-10 system is used worldwide by doctors, hospitals, and insurance companies. Every diagnosis has its own unique code.
When your doctor writes down the ICD-10 code ACL tear, they are doing three things:
- Recording your exact condition in your medical record.
- Telling your insurance company why you need treatment.
- Helping researchers track how common knee injuries are.
Without the correct code, your claim might be denied. You might also receive a bill for services that should have been covered. So getting the code right is not just paperwork — it directly affects your wallet and your care.
The Main ICD-10 Code for ACL Tear
The primary code you will see for an ACL tear is:
S83.512A – Anterior cruciate ligament tear, left knee, initial encounter
But wait — there is more than one code. The full family of ACL tear codes looks like this:
| Code | Description |
|---|---|
| S83.511A | ACL tear, right knee, initial encounter |
| S83.512A | ACL tear, left knee, initial encounter |
| S83.513A | ACL tear, unspecified knee, initial encounter |
| S83.511D | ACL tear, right knee, subsequent encounter |
| S83.512D | ACL tear, left knee, subsequent encounter |
| S83.513D | ACL tear, unspecified knee, subsequent encounter |
| S83.511S | ACL tear, right knee, sequela (long-term effect) |
| S83.512S | ACL tear, left knee, sequela |
| S83.513S | ACL tear, unspecified knee, sequela |
Let us break that down so it makes sense.
Initial vs. Subsequent vs. Sequela
- Initial encounter (A): The first time you receive active treatment. This includes the emergency room visit, the orthopedic consultation, and the early decisions about surgery or bracing.
- Subsequent encounter (D): Follow-up visits during healing or rehab. For example, a physical therapy session six weeks after injury.
- Sequela (S): Late effects of the injury. This could be chronic knee instability, arthritis, or stiffness that remains after the tear has healed or been surgically repaired.
Left, Right, or Unspecified
Always use left or right if you know which knee is injured. Insurance companies often reject claims with “unspecified” codes unless there is a good reason. Only use S83.513A if the medical record truly does not say which knee.
Complete List of ACL Tear ICD-10 Codes (Expanded)
The S83 category covers all knee ligament injuries. For a pure ACL tear without other damage, you will stay within S83.51. However, sometimes the ACL tears along with other ligaments. Here is the full table:
| ICD-10 Code | Description |
|---|---|
| S83.511A | ACL tear, right knee, initial |
| S83.512A | ACL tear, left knee, initial |
| S83.513A | ACL tear, unspecified knee, initial |
| S83.511D | ACL tear, right knee, subsequent |
| S83.512D | ACL tear, left knee, subsequent |
| S83.513D | ACL tear, unspecified knee, subsequent |
| S83.511S | ACL tear, right knee, sequela |
| S83.512S | ACL tear, left knee, sequela |
| S83.513S | ACL tear, unspecified knee, sequela |
| S83.52 | Complex ACL tear (involving other knee structures) |
Note: The “complex” code (S83.52) is used when the ACL tear happens together with a meniscus tear, MCL tear, or fracture. Your surgeon will decide this after an MRI.
How Doctors Diagnose an ACL Tear (And How That Affects Coding)
Before any code is assigned, your doctor needs to confirm the tear. The process usually follows these steps:
- Physical exam – The Lachman test and pivot shift test are very accurate for ACL tears.
- MRI – This is the gold standard. It shows the tear grade and any other damage.
- X-ray – This does not show ligaments, but it rules out bone fractures.
Only after a confirmed diagnosis does the doctor assign the ICD-10 code ACL tear. If the MRI is not yet done, the doctor may use a temporary code like M23.5 (chronic instability of knee) or S83.9 (unspecified ligament tear). Once the MRI confirms an ACL tear, they update the record.
Important for patients: If you see a code like S83.9 on your first visit summary, do not panic. It just means the final diagnosis was not yet confirmed. Ask your doctor to update it after the MRI.
Acute vs. Chronic ACL Tear: Does the Code Change?
This is a common question. The short answer is: the code does not directly say “acute” or “chronic,” but the encounter letter implies it.
- Initial encounter (A) is almost always used for an acute tear — one that happened within the past few weeks.
- Sequela (S) is used for chronic problems from an old tear. For example, if you tore your ACL two years ago and now you have knee buckling, the code would be S83.512S (left knee, sequela).
If you have a chronic ACL tear but are seeking surgery for the first time, many coders will still use the initial encounter (A) because you are beginning active treatment. Medical coding guidelines allow this as long as the treatment is for the tear itself, not just late effects.
Real-Life Examples (Helps You Match Your Situation)
Let us look at three different people and see which code applies.
Example 1: Sarah, 24, soccer player
Sarah twists her knee during a match. She hears a pop. The ER doctor orders an MRI, which shows a complete ACL tear in her right knee. She sees an orthopedic surgeon the next week.
- Correct code: S83.511A (right knee, initial encounter)
Example 2: James, 47, weekend runner
James tore his left ACL five years ago. He never had surgery. Now his knee gives way when he walks downstairs. He sees a physiatrist for bracing and physical therapy.
- Correct code: S83.512S (left knee, sequela)
Example 3: Maria, 33, returns for follow-up
Maria had ACL reconstruction surgery six weeks ago. She is in physical therapy and sees her surgeon for a check-up. No new injury.
- Correct code: S83.511D (right knee, subsequent encounter)
Common Billing Mistakes and How to Avoid Them
Insurance denials for ACL tears are often caused by small coding errors. Here are the most frequent problems:
| Mistake | Consequence | Fix |
|---|---|---|
| Using unspecified knee (S83.513A) when the MRI shows laterality | Claim delayed or denied | Ask your doctor to add left or right |
| Using initial encounter (A) for a follow-up visit | Insurance may overpay and later claw back money | Use D for routine follow-ups |
| Using sequela (S) for an acute injury | Wrong payment category; rehab may not be covered | Use A for the first 3–6 months |
| Forgetting to add external cause code | Some plans require how the injury happened | Add W01.0 (fall on same level) or V93.4 (sports) as needed |
Pro tip: Keep a copy of your MRI report. It will clearly say “right ACL tear” or “left ACL tear.” Give that report to every new provider so they use the correct code.
How to Talk to Your Doctor About the Code
You have every right to ask about your medical codes. Here is a simple script you can use:
“I see a code on my visit summary. Can you confirm that this is the correct ICD-10 code for my ACL tear? And does it show the right knee and initial visit?”
Most doctors and medical coders are happy to explain. If you spot an error — for example, they coded the left knee instead of the right — ask them to correct it before you leave the office. A correction later takes weeks. A correction now takes two minutes.
Frequently Asked Questions (FAQ)
1. Is there a separate ICD-10 code for a partial ACL tear?
No. The codes S83.511A through S83.513S do not distinguish between partial (grade 2) and complete (grade 3) tears. Both use the same code. Only the MRI report and doctor’s notes clarify the severity.
2. What is the ICD-10 code for ACL tear with meniscus tear?
If the ACL tear is the primary diagnosis, you still use S83.511A (or left/right). The meniscus tear is added as a secondary code: S83.2 (tear of medial or lateral meniscus). You never combine them into one code.
3. Can I use an ACL tear code for a sprain?
No. An ACL sprain (grade 1) is coded as S83.511A as well. The ICD-10 system does not separate sprain from tear for the ACL. Both use the same code family. This surprises many people, but it is correct.
4. What code should I use for an old ACL tear that is now causing arthritis?
You would use two codes:
- S83.512S for the old ACL tear (sequela)
- M17.9 for knee arthritis
The arthritis is a separate condition, even if the ACL tear caused it.
5. Do I need a different code for a reconstructed ACL that tears again?
Yes. If you had ACL surgery and the graft tears, this is considered a new injury. You go back to S83.511A (initial encounter) because you are starting active treatment again for a new tear.
Additional Resources
For more official information on ICD-10 coding for knee injuries, visit the Centers for Medicare & Medicaid Services (CMS) 2025 ICD-10 CM Guidelines.
🔗 CMS Official ICD-10 Portal (opens in new tab)
This is the most trusted source for accurate, up-to-date codes. Avoid private “coding cheat sheets” that may be outdated.
Important Notes for Readers
- Do not use these codes to bill insurance yourself unless you are a trained medical coder. Always work with your provider’s billing department.
- Codes can change every October 1. The information in this article is based on the 2025 ICD-10 CM release.
- If your insurance denies a claim, ask for the specific reason. Often it is a missing letter (A, D, or S) rather than a wrong main code.
- Keep a personal health record with your diagnosis codes. It helps if you change doctors or move to another state.
Conclusion
The ICD-10 code for an ACL tear depends on three things: which knee, whether it is the first visit or a follow-up, and if you are dealing with long-term effects. The primary codes are S83.511A (right), S83.512A (left), and S83.513A (unspecified). Use the letter A for initial treatment, D for subsequent care, and S for chronic problems. Always specify left or right to avoid insurance delays. When in doubt, ask your doctor or a certified medical coder for help.
Disclaimer: This article is for informational and educational purposes only. It does not constitute medical advice or legal coding advice. Always consult with a qualified healthcare provider or certified professional coder for your specific situation. Medical codes are updated annually; verify current codes before submitting any claim.
