Updated August 17, 2026

Bibliography

Sources and methods

Every study cited on this site, with its journal, year and PubMed identifier. This list is generated from the same table the pages read from, so a citation cannot exist here without existing there.

Studies and guidelines

• Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. British Journal of Sports Medicine, 2016;50(13):804-808. PubMed 27162233. 106 pivoting-sport patients, prospective two-year cohort.
• Beischer S, Gustavsson L, Senorski EH, Karlsson J, Thomee C, Samuelsson K, Thomee R. Young athletes who return to sport before 9 months after anterior cruciate ligament reconstruction have a rate of new injury 7 times that of those who delay. Journal of Orthopaedic and Sports Physical Therapy, 2020;50(2):83-90. PubMed 32005095. 159 athletes aged 15 to 30, rehabilitation registry, Cox model.
• Kyritsis P, Bahr R, Landreau P, Miladi R, Witvrouw E. Likelihood of ACL graft rupture: not meeting six clinical discharge criteria before return to sport is associated with a four times greater risk of rupture. British Journal of Sports Medicine, 2016;50(15):946-951. PubMed 27215935. 158 male professional athletes, median follow-up 646 days.
• Losciale JM, Zdeb RM, Ledbetter L, Reiman MP, Sell TC. The association between passing return-to-sport criteria and second anterior cruciate ligament injury risk: a systematic review with meta-analysis. Journal of Orthopaedic and Sports Physical Therapy, 2019;49(2):43-54. PubMed 30501385. Systematic review, 4 studies, meta-analysis.
• Wiggins AJ, Grandhi RK, Schneider DK, Stanfield D, Webster KE, Myer GD. Risk of secondary injury in younger athletes after anterior cruciate ligament reconstruction: a systematic review and meta-analysis. American Journal of Sports Medicine, 2016;44(7):1861-1876. PubMed 26772611. Systematic review and meta-analysis, 19 studies.
• Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport. American Journal of Sports Medicine, 2014;42(7):1567-1573. PubMed 24753238. Cohort of athletes followed for 24 months after their return, with healthy controls.
• Paterno MV, Huang B, Thomas S, Hewett TE, Schmitt LC. Clinical factors that predict a second ACL injury after ACL reconstruction and return to level I sports. Orthopaedic Journal of Sports Medicine, 2017;5(12). PubMed 29318172. 114 patients, classification tree (CART).
• Webster KE, Feller JA, Leigh WB, Richmond AK. Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction. American Journal of Sports Medicine, 2016;44(11):2827-2832. PubMed 27390346. 316 patients followed, 89 per cent follow-up rate.
• McPherson AL, Feller JA, Hewett TE, Webster KE. Psychological readiness to return to sport is associated with second anterior cruciate ligament injuries. American Journal of Sports Medicine, 2019;47(4):857-862. PubMed 30753794. 329 patients back in sport, ACL-RSI score.
• McPherson AL, Feller JA, Hewett TE, Webster KE. Smaller change in psychological readiness to return to sport is associated with second anterior cruciate ligament injury among younger patients. American Journal of Sports Medicine, 2019;47(5):1209-1215. PubMed 30786247. 115 younger patients back in sport.
• Capin JJ, Arundale AJH, Bradley H, et al.. Female athletes with better psychological readiness at return to sport were more likely to sustain a second ACL injury. Sports Health, 2024;16(1):149-154. PubMed 36935576. Elite female athletes, ACL-SPORTS, two-year follow-up.
• Kaeding CC, Aros B, Pedroza A, et al. (MOON Group). Allograft versus autograft anterior cruciate ligament reconstruction: predictors of failure from a MOON prospective longitudinal cohort. Sports Health, 2011;3(1):73-81. PubMed 23015994. Prospective multicentre MOON cohort.
• Ardern CL, Taylor NF, Feller JA, Webster KE. Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors. British Journal of Sports Medicine, 2014;48(21):1543-1552. PubMed 25157180. 69 papers, 7,556 participants.
• Frobell RB, Roos EM, Roos HP, Ranstam J, Lohmander LS. A randomized trial of treatment for acute anterior cruciate ligament tears. New England Journal of Medicine, 2010;363(4):331-342. PubMed 20660401. 121 young active adults, randomised trial (KANON).
• 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. PubMed 23349407. Five-year follow-up of the same trial.
• Filbay SR, Roemer FW, Lohmander LS, et al.. Evidence of ACL healing on MRI following ACL rupture treated with rehabilitation alone may be associated with better patient-reported outcomes. British Journal of Sports Medicine, 2023;57(2):91-98. PubMed 36328403. Secondary MRI analysis of the KANON trial.
• Sturgill LP, Snyder-Mackler L, Manal TJ, Axe MJ. Interrater reliability of a clinical scale to assess knee joint effusion. Journal of Orthopaedic and Sports Physical Therapy, 2009;39(12):845-849. PubMed 20032559. 75 test pairs, two therapists.
• Failla MJ, Logerstedt DS, Grindem H, et al.. Does extended preoperative rehabilitation influence outcomes 2 years after ACL reconstruction? A comparative effectiveness study between the MOON and Delaware-Oslo ACL cohorts. American Journal of Sports Medicine, 2016;44(10):2608-2614. PubMed 27416993. Comparison of two cohorts, with and without extended preoperative preparation.
• Mall NA, Chalmers PN, Moric M, et al.. Incidence and trends of anterior cruciate ligament reconstruction in the United States. American Journal of Sports Medicine, 2014;42(10):2363-2370. PubMed 25086064. United States national databases, 1994 to 2006. Cited here only as an order of magnitude for how common the procedure is.
• Gans I, Retzky JS, Jones LC, Tanaka MJ. Epidemiology of recurrent anterior cruciate ligament injuries in National Collegiate Athletic Association sports: the Injury Surveillance Program, 2004-2014. Orthopaedic Journal of Sports Medicine, 2018;6(6). PubMed 29977938. 350,416 NCAA athlete-exposures, 1,105 ACL tears including 126 re-tears.
• Logerstedt DS, Scalzitti D, Risberg MA, et al.. Knee stability and movement coordination impairments: knee ligament sprain revision 2017. Clinical practice guidelines linked to the International Classification of Functioning, Disability and Health. Journal of Orthopaedic and Sports Physical Therapy, 2017;47(11):A1-A47. PubMed 29089004. Clinical practice guideline from the Academy of Orthopaedic Physical Therapy (APTA).
• Nagelli CV, Hewett TE. Should return to sport be delayed until 2 years after anterior cruciate ligament reconstruction? Biological and functional considerations. Sports Medicine, 2017;47(2):221-232. PubMed 27402457. Narrative review of the biological and functional evidence.
• Ithurburn MP, Zbojniewicz AM, Thomas S, et al.. Young athletes after ACL reconstruction with asymmetric quadriceps strength at the time of return to sport favor their uninvolved limb during landing two years later. The Knee, 2021;29:520-529. PubMed 33756262. 54 young athletes, vertical drop jump two years after their return to sport.
• Kotsifaki R, Korakakis V, King E, et al. Aspetar clinical practice guideline on rehabilitation after anterior cruciate ligament reconstruction. British Journal of Sports Medicine, 2023;57(9):500-514. Read the publication. Clinical practice guideline built with the GRADE method: progression driven by objective criteria rather than the calendar alone, early strengthening, explicit criteria for returning to running and to sport.
• Poulsen E, Goncalves GH, Bricca A, Roos EM, Thorlund JB, Juhl CB. Knee osteoarthritis risk is increased 4-6 fold after knee injury: a systematic review and meta-analysis. British Journal of Sports Medicine, 2019;53(23):1454-1463. Read the publication. Systematic review and meta-analysis, 53 studies, close to one million participants. Knee osteoarthritis risk is 4.2 times higher after an ACL injury and 6.3 times higher after a meniscal injury, with at least two years of follow-up.
• van Melick N, van Cingel REH, Brooijmans F, et al. Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus. British Journal of Sports Medicine, 2016;50(24):1506-1515. Read the publication. Systematic review and multidisciplinary consensus. Rehabilitation should be criterion-based, include preoperative preparation, neuromuscular work and strength, and continue well beyond the first months.
• Filbay SR, Grindem H. Evidence-based recommendations for the management of anterior cruciate ligament (ACL) rupture. Best Practice and Research Clinical Rheumatology, 2019;33(1):33-47. Read the publication. Evidence-based review. Three strategies coexist: rehabilitation first, early surgery, or prehabilitation then surgery. None is superior for everyone: the decision depends on the profile, the associated injuries and the goals.
• Filbay SR, Bullock G, Russell S. No difference in return-to-sport rate or activity level in people with anterior cruciate ligament (ACL) injury managed with ACL reconstruction or rehabilitation alone: a systematic review and meta-analysis. Sports Medicine, 2025;55(9):2191-2205. PubMed 40603829. Systematic review and meta-analysis, 15 studies, low to very low certainty. Return-to-sport rate and activity level do not differ significantly between reconstruction and rehabilitation alone, and the low level of certainty calls for caution.
• Ardern CL, Glasgow P, Schneiders A, et al. 2016 Consensus statement on return to sport from the First World Congress in Sports Physical Therapy, Bern. British Journal of Sports Medicine, 2016;50(14):853-864. Read the publication. International consensus statement. Return to sport is a three-stage continuum (return to participation, return to sport, return to performance) and a shared decision, never a single isolated test.
• Webster KE, Feller JA, Lambros C. Development and preliminary validation of a scale to measure the psychological impact of returning to sport following anterior cruciate ligament reconstruction surgery. Physical Therapy in Sport, 2008;9(1):9-15. PubMed 19083699. Scale development and preliminary validation. The ACL-RSI scale measures confidence, apprehension and fear of reinjury: it puts a number on the psychological side of returning to sport.
• Roos EM, Roos HP, Lohmander LS, Ekdahl C, Beynnon BD. Knee Injury and Osteoarthritis Outcome Score (KOOS): development of a self-administered outcome measure. Journal of Orthopaedic and Sports Physical Therapy, 1998;28(2):88-96. Read the publication. Scale development and validation. The KOOS score covers pain, symptoms, daily function, sport function and knee-related quality of life: it is the reference questionnaire for longitudinal follow-up.

Official United States documents

• 2026 maximum annual limitation on cost sharing. $10,600 for self-only coverage and $21,200 for other than self-only coverage, for non-grandfathered plans, plan years beginning in 2026. HHS revised this figure upward in a June 2025 final rule; it replaces the $10,150 and $20,300 announced earlier. Source: US Department of Health and Human Services and CMS, Marketplace regulations and guidance.
• 2026 Medicare therapy threshold. Medicare's KX modifier threshold for physical therapy and speech-language pathology combined is $2,480 for calendar year 2026. Past that amount, claims must carry the KX modifier and the record must justify continued care. A separate targeted medical review threshold sits at $3,000. Source: Centers for Medicare and Medicaid Services, therapy services.
• No Surprises Act. Since January 2022, out-of-network providers who treat you at an in-network facility generally cannot balance bill you above your in-network cost sharing for emergency care and for many non-emergency services, including anesthesia and assistant surgeons. Source: Centers for Medicare and Medicaid Services, No Surprises Act.
• Good Faith Estimate. If you are uninsured or paying cash, providers must give you a written good faith estimate of expected charges before a scheduled service, and you can dispute a final bill that exceeds it by $400 or more. Source: Centers for Medicare and Medicaid Services, No Surprises Act, good faith estimates.
• Hospital price transparency. Hospitals must publish a machine-readable file of standard charges, including payer-specific negotiated rates, and a consumer-friendly display of shoppable services. An ACL reconstruction is a shoppable service. Source: Centers for Medicare and Medicaid Services, hospital price transparency.

How to read a citation on this site

When a page says something like reinjury fell 51% for each month return was delayed up to 9 months, that sentence is the study's own result, in the study's own population. It is not a rule for your knee, and the page will say which cohort it came from.

Where studies conflict, both appear. The clearest case: Grindem 2016 found that 38.2% of athletes who failed return-to-sport criteria were reinjured versus 5.6% of those who passed, while Losciale 2019, pooling four studies, found a non-significant 3% risk difference at very low quality of evidence. Both are on the testing page.

What is deliberately absent

An average billed price for ACL reconstruction in the United States, an average employer deductible, and a universal ACL-RSI cut-off. None of the three could be traced to a primary source we can stand behind. The about page explains what we publish instead.