ACL Non-Operative Treatment Risk Estimator — For Patients Under 16
Built and validated in adolescents — but many adults and highly active patients find the same framework useful when thinking through surgery vs. rehabilitation first. See notes below if you're over 16.
If you're an adult, or a highly active athlete — read this first
Choosing non-operative treatment as an adult doesn't mean "no surgery, full stop" — it means trying structured rehabilitation first and keeping surgery as an option if you need it later. In a cohort of adults with acute ACL tears who initially chose non-operative treatment, roughly two-thirds went on to manage well without surgery, while about a third later converted to surgery because of ongoing knee instability during sport.1 A separate randomised trial found similar patient-reported outcomes at 2 and 5 years whether patients had early surgery or tried rehabilitation first with surgery only if needed — and more than 6 in 10 of those given that option avoided surgery altogether.2,3
This means many adults are in no rush to decide. You can start with rehabilitation, see how the knee responds, and decide on surgery later if instability persists, without it costing you a worse long-term outcome. The trade-off: repeated episodes of the knee "giving way" do carry a real risk of further meniscus and cartilage damage, so this window isn't indefinite — a surgeon's input helps judge when watchful waiting has run its course.
Historically, patients who do well with rehabilitation alone are called "copers," and those who don't are "non-copers" — but there's no perfect test to sort people into either group in advance. A systematic review found that neither sex nor knee laxity testing reliably predicts who will fail non-operative treatment, and most other proposed predictors have weak or conflicting evidence.4 What is consistent: patients wanting to return to competitive pivoting, cutting, and jumping sports (soccer, basketball, handball) are the group most likely to experience instability without surgery. Patients who are sedentary, or willing to shift toward lower-demand, non-pivoting activity (cycling, swimming, running, strength training), often do well without ever needing reconstruction.1
This is why a high score on this calculator should never be read as "you must have surgery." The algorithm reflects a statistical association seen in the original adolescent study population — it doesn't account for your sport, your weight, your meniscus status, or your willingness to change your activity level, all of which materially change your real-world odds. Whether to reconstruct the ACL is ultimately a personal, lifestyle-based decision made together with your surgeon — not a verdict from any single score.
- 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.
- 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.
- 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.
- Eggerding V, Meuffels DE, Bierma-Zeinstra SMA, Verhaar JA, Reijman M. Factors related to the need for surgical reconstruction after anterior cruciate ligament rupture: a systematic review of the literature. J Orthop Sports Phys Ther. 2015;45(1):37-44.
Your details
Required so your result can be labelled and saved as a personal report.
1. Growth plate status up to 2 pts
This affects how much your knee's ligaments are expected to stretch or fail with instability.
Please select your sex and, if your MRI report or surgeon has stated it, your skeletal (bone) age:
2. Meniscal tear pattern on MRI up to 3 pts
Taken from your radiologist's MRI report. Select the option that best matches — if more than one tear is mentioned, select the more severe.
3. Bone bruising pattern on MRI 1 pt
Look for mention of bone bruising / bone marrow oedema on the outer (lateral) side of the knee — this is very common with ACL injuries.
4. How the injury happened 1 pt
5. Pivot-shift test result 1 pt
This is a hands-on knee exam done by a surgeon or physiotherapist — it cannot be assessed by yourself, and many patients won't yet know this result. If you're unsure, choose "Not assessed."
Score breakdown
Interpretation
A high score here doesn't mean surgery is mandatory. Many adults do well starting with rehabilitation and deciding on surgery later if instability persists — outcomes are often similar either way, especially with non-pivoting sports, lower activity demands, or a willingness to modify lifestyle. Ongoing giving-way episodes do raise the risk of further meniscus/cartilage damage over time, so this is a decision made with your surgeon — not a verdict from this score alone.
Grindem et al. 2014 (JBJS); Frobell et al. 2010 (NEJM) / 2013 (BMJ).What this score has meant in the original study
These figures come from a single study of 75 growing patients (55 surgical, 20 initially non-surgical). They are a guide to typical outcomes in that specific group — not a personalised prediction, and not yet confirmed in adults or in larger studies.
For additional context: average scores by outcome in the original study
| Treated surgically from the start | 5.6 | |
| Non-op initially, later failed & needed surgery | 4.7 | |
| Non-op initially, successful (no surgery needed) | 2.1 |
This shows a general trend — higher scores were associated with surgical treatment and with non-operative treatment failing — but these are group averages, not a per-point risk calculation, and shouldn't be read as "each extra point adds X% risk."
Adapted from: Grassi A, Borque K, Dietvorst M, et al. Creation and validation of a treatment algorithm for skeletally immature patients with acute anterior cruciate ligament injury based on MRI and patient characteristics. J Exp Orthop. 2025;12:e70280.