Having a Revision ACL Reconstruction Is Worse Than Tearing the Contralateral ACL and Undergoing Reconstruction: A MOON Cohort Study

Abstract

Background:

Anterior cruciate ligament (ACL) graft tears and contralateral ACL tears are both relatively common after primary ACL reconstruction (ACLR). There is little prior work comparing the outcomes of reconstruction after these injuries.

Hypothesis:

The authors hypothesize that patient-reported outcome measures (PROMs) and activity level are lower after revision ACLR than after primary contralateral ACLR.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

From a cohort of 2333 patients who underwent primary unilateral ACLR, 267 were identified who underwent subsequent revision ACLR or primary contralateral ACLR within 5 years of primary ACLR. After exclusion of 11 patients who had both injuries, 256 were eligible for the study, including 124 who underwent revision ACLR and 132 who underwent primary contralateral ACLR. Patients were contacted for follow-up at 6 years after the primary ACLR, and PROMs were collected, including subjective International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score for pain (KOOS-Pain) and knee-related quality of life (KOOS-QOL), and Marx activity level. Patient demographics, surgical factors, and PROMs were compared between groups. Beta regression models with identity link were used to determine whether side of subsequent surgery (revision vs primary contralateral ACLR) was a significant predictor of outcome.

Results:

Of 256 patients, 223 (87%) were contacted and completed PROMs at 6 years after the primary ACLR. At baseline, there were no significant differences between groups except that the subsequent revision group had a lower incidence of partial lateral meniscectomy and a higher incidence of lateral meniscal repair and was more likely to have received allograft for the primary ACLR than the subsequent contralateral reconstruction group. The median time from primary ACLR to second ACL surgery was lower in the revision group (1.3 years) than the contralateral group (2.0 years; P < .001). When controlling for demographics, surgical factors, and baseline PROMS, the revision ACL group demonstrated a 7.8-point lower International Knee Documentation Committee score (P < .001), a 3.2-point lower KOOS-Pain score (P = .012), a 10.4-point lower KOOS-QOL score (P < .001), and 2.0-point lower Marx score (P = .002) than the contralateral ACLR group.

Conclusion:

Patients who undergo revision ACLR within 5 years of primary ACLR demonstrate poorer PROMs and lower activity levels than those who undergo primary contralateral ACLR during this period. These 2 groups of patients should not be pooled to study outcomes of ACLR.

Keywords

knee general ACL ligaments general sports trauma

Anterior cruciate ligament (ACL) injuries occur frequently and are commonly treated with ACL reconstruction (ACLR) in young, active patients.⁸ In spite of advances in surgical and rehabilitation techniques, ACL graft tears and contralateral ACL tears are relatively common after primary ACLR. While variable across studies, ACL graft tear risk and contralateral ACL injury risk are reported between 2% and 15% and even higher in certain populations.^34,37

Patients with graft tears that are treated with revision ACLR generally report poorer patient-reported outcome measures (PROMs) and engage in lower activity levels than patients who undergo primary ACLR.^11,20,35 Multiple prior studies have identified patient and surgical factors that are associated with increased risk of graft failure and revision surgery, including younger age, higher activity levels, high-grade preoperative knee laxity, increased posterior tibial slope, and the use of allograft tissue in younger patients.^{9,15,16,18,24} Hamstring autografts have also demonstrated increased failure risk relative to bone–patellar tendon–bone autografts in younger, more active patients, particularly in females and when performed in the absence of a lateral extra-articular procedure.^19,22,26,29

While less research has focused on patients with subsequent contralateral tears and reconstruction, limited work suggests that their outcomes may be more similar to those of primary ACLR.⁵ The risk factors most associated with contralateral tears are younger age and higher activity level.^6,32 The use of patellar tendon autografts for primary ACLR has been noted in some studies to be associated with an increased risk of contralateral ACL injuries.^27,28

A current trend in reporting outcomes after ACL surgery has been identification of risk factors for “subsequent cruciate injury,” defined as an injury to either the graft or contralateral ACL after ACLR.^1,7,10,25,34 Utilization of this outcome measure is useful as it increases the number of “events” and the power of these studies, allowing for multiple logistic regression analyses with relatively smaller cohort sizes. One major limitation of utilizing subsequent cruciate ligament injury as an outcome variable is the assumption that these injuries have a similar deleterious effect on patient-reported outcomes.

Review of the literature has identified no studies comparing the outcomes of patients with ACL graft tears treated with revision reconstruction with those who have a contralateral ACL tear and subsequent reconstruction after primary ACLR. We hypothesize that PROMs and activity level are lower after revision ACLR than after primary contralateral ACLR.

Methods

Patients

From an institutional review board–approved prospective cohort study of 2333 patients with ACL injury who underwent primary unilateral ACLR at academic medical centers in the United States between 2002 and 2008, 267 patients were identified who underwent revision ACLR or primary contralateral ACLR within 5 years of primary ACLR. After the exclusion of 11 patients who had both injuries, 256 patients were eligible for study inclusion, including 124 who underwent revision ACLR and 132 who underwent primary contralateral ACLR (Figure 1).

Data Collection

Demographic data included patient age, sex, body mass index, smoking status (current vs nonsmoker or past smoker), and sport at original injury. Patients also completed preoperative PROMs, such as the subjective International Knee Documentation Committee (IKDC) score,¹³ Knee injury and Osteoarthritis Outcome Score for pain (KOOS-Pain) and knee-related quality of life (KOOS-QOL),³⁰ and Marx activity level.²¹

At the time of primary ACLR, the operating surgeon documented arthroscopic findings and surgical technique, which included graft type as well as meniscal and cartilage pathology and treatment and an examination of knee laxity under anesthesia. Meniscal status was classified as normal, stable meniscal tear without treatment, meniscal repair, or partial meniscectomy. Articular cartilage status was dichotomized according to the modified Outerbridge scale as normal/grade 1 or grade 2, 3, or 4.²³ Knee laxity was assessed with Lachman, anterior drawer, and pivot-shift tests and classified according to the IKDC system.¹² Patients were classified as having high-grade knee laxity if they had a 3+ Lachman, anterior drawer, or pivot shift under anesthesia.¹⁷

Patients were followed prospectively and at the 6-year mark after their index ACLR (minimum 1 year after their subsequent ACL surgery), and they were contacted by mail and/or phone to complete the same PROMs that were collected preoperatively. Follow-up >90% was the goal to minimize selection bias.

Statistical Analysis

Continuous variables were summarized by median and interquartile range after normality testing demonstrated skewed distributions, and categorical variables were summarized by count and percentage. PROMs at 6 years after primary ACLR and other patient and surgical factors were compared between those who underwent revision ACLR and those who underwent primary contralateral ACLR. Continuous variables were compared with Mann-Whitney U tests and categorical variables with Fisher exact tests.

Multivariable models were built to compare outcomes based on subsequent surgery, controlling for potential confounders by identity link beta regression for 6-year outcomes.⁴ Beta regression utilizes outcome variables between 0 and 1 (exclusive). Therefore, 6-year IKDC, KOOS-Pain, and KOOS-QOL were transformed as follows: 0 was recoded as 0.002, 100 as 0.998, and all other values as the original score divided by 100. Six-year Marx was transformed as follows: 0 was recoded as 0.02, 16 as 0.998, and all other values as the original score divided by 16. After the models were fit, the coefficient estimates were transformed back to the original scale for easier interpretation. Rescaled coefficient estimates and their 95% confidence intervals were calculated. All tests were 2-sided, and statistically significant findings were defined as P < .05.

A power analysis demonstrated that a minimum 37 patients per group was required to achieve 80% power to detect a clinically relevant 10-point difference in KOOS subscales with an expected standard deviation of 15 points with an alpha of .05.³⁶ Data management and analysis were performed in R software (Version 4.0).

Results

Of the 256 patients who underwent subsequent cruciate ligament surgery within 5 years of primary ACLR, 233 (87%) completed PROMs 6 years after their primary ACLR. This timing corresponded to a median 4.4 years (minimum, 1 year) after their second ACL procedure (revision or primary contralateral ACLR).

The median age of the 256 patients at primary ACLR was 17.0 years (IQR, 15-23), and their median body mass index was 23.1 kg/m² (IQR, 21.2-26.2). There were 139 male patients (54%) and 117 female patients (46%) and 20 current or recent smokers (8%). High-grade laxity (IKDC 3+) was noted on the Lachman, pivot shift, and/or anterior drawer in 105 patients (41%). Sports at injury included basketball (n = 77, 30%), football (n = 47, 18%), soccer (n = 52, 20%), other sports (n = 61, 24%), and nonsports activities (n = 19, 7%). No differences in demographics or injury factors were noted between the groups (Table 1).

Table 1

Baseline Patient Characteristics ^a

	Group, Median (IQR) or No. (%)
	Revision ACLR (n = 124)	Contralateral ACLR (n = 132)	P Value
Age, y	18.0 (16.0-21.2)	17.0 (15.0-24.0)	.97
Sex			.30
Male	72 (58.1)	67 (50.8)
Female	52 (41.9)	65 (49.2)
Body mass index, kg/m²	23.0 (21.6-25.8)	23.3 (21.1-26.4)	.99
Smoking			.73
Nonsmokers and past smokers	113 (91.1)	121 (93.1)
Current smokers	11 (8.9)	9 (6.9)
Sport at initial injury			.13
None	8 (6.5)	11 (8.3)
Basketball	29 (23.4)	48 (36.4)
Football	28 (22.6)	19 (14.4)
Soccer	26 (21.0)	26 (19.7)
Other	33 (26.6)	28 (21.2)
IKDC	51.3 (35.6-67.0)	53.2 (38.8-67.6)	.32
KOOS
Pain	76.4 (63.2-88.9)	75.0 (63.9-86.1)	.95
QOL	37.5 (25.0-50.0)	37.5 (18.8-50.0)	.57
Marx activity level	16.0 (12.8-16.0)	16.0 (12.0-16.0)	.51

ACLR, anterior cruciate ligament reconstruction; IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; QOL, knee-related quality of life.

At the time of the index ACL surgery, medial meniscal tears were treated in 82 patients (32%), including 39 repairs and 43 medial meniscectomies. Lateral meniscal tears were treated in 97 patients (38%), including 74 repairs and 23 partial lateral meniscectomies. Articular cartilage damage of Outerbridge grade 2, 3, or 4 was identified in the medial compartment in 50 patients, in the lateral compartment in 35, and in the patellofemoral compartment in 30. The subsequent ACL revision group demonstrated a lower incidence of partial lateral meniscectomy and a higher incidence of lateral meniscal repair, but no other differences in intra-articular pathology were identified between the groups (Table 2).

Table 2

Baseline Surgical Characteristics ^a

	Group, No. (%) or Median (IQR)
	Revision ACLR (n = 124)	Contralateral ACLR (n = 132)	P Value
High-grade laxity			.87
No	72 (58.1)	79 (59.8)
Yes	52 (41.9)	53 (40.2)
Graft type			<.001
BTB autograft	37 (29.8)	66 (50.0)
Hamstring autograft	49 (39.5)	51 (38.6)
Allograft	38 (30.6)	15 (11.4)
Medial meniscal treatment			.73
None	92 (74.2)	92 (69.7)
Partial meniscectomy	17 (13.7)	22 (16.7)
Repair	15 (12.1)	18 (13.6)
Lateral meniscal treatment			.038
None	83 (66.9)	76 (57.6)
Partial meniscectomy	27 (21.8)	47 (35.6)
Repair	14 (11.3)	9 (6.8)
Lateral cartilage status			.87
Grade 0 / 1	108 (87.1)	113 (85.6)
Grade 2 / 3/ 4	16 (12.9)	19 (14.4)
Medial cartilage status			.39
Grade 0 / 1	103 (83.1)	103 (78.0)
Grade 2 / 3/ 4	21 (16.9)	29 (22.0)
Patellofemoral cartilage status			.99
Grade 0 / 1	109 (87.9)	117 (88.6)
Grade 2 / 3 / 4	15 (12.1)	15 (11.4)
Time from primary ACLR to second surgery, y	1.30 (0.90-2.15)	2.00 (1.30-3.02)	<.001

ACLR, anterior cruciate ligament reconstruction; BTB, bone–patellar tendon–bone.

Primary ACLR was performed with bone–patellar tendon–bone autograft in 103 patients (40%), hamstring autograft in 100 (39%), and allograft in 53 (21%). The subsequent primary contralateral ACL group was more likely to have had a bone–patellar tendon–bone graft for the primary reconstruction, while the revision group was more likely to have had an allograft (Table 2). The median time from primary ACLR to second cruciate ligament reconstruction was 1.7 years and was longer in the contralateral ACLR group than in the revision group.

There were no differences in preoperative IKDC score, KOOS-Pain, or KOOS-QOL between the groups. This cohort was a highly active group with a median Marx activity score of 16. No differences in Marx scores were noted between the groups (Table 3).

Table 3

Preoperative Patient-Reported Outcomes ^a

	Group, Median (IQR)
	Revision ACLR	Contralateral ACLR	P Value
IKDC	52.3 (42.0-63.0)	53.2 (43.5-63.0)	.32
KOOS
Pain	76.4 (63.2-88.9)	75.0 (63.9-86.1)	.95
QOL	37.5 (25.0-50.0)	37.5 (18.8-50.0)	.57
Marx activity level	16.0 (12.8-16.0)	16.0 (12.0-16.0)	.51

ACLR, anterior cruciate ligament reconstruction; IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; QOL, knee-related quality of life.

At follow-up, patients who underwent revision ACLR demonstrated significantly lower KOOS-Pain, KOOS-QOL, and IKDC scores than those who underwent a subsequent primary contralateral ACLR (Table 4). The revision reconstruction group was also noted to have a significantly lower Marx activity score.

Table 4

Patient-Reported Outcomes 6 Years After Primary ACLR ^a

	Group, Median (IQR)
	Revision ACLR (n = 108)	Contralateral ACLR (n = 115)	P Value
IKDC	80.5 (67.8-89.7)	89.7 (78.8-96.0)	<.001
KOOS
Pain	91.7 (80.6-97.2)	94.4 (87.5-100)	.009
QOL	68.8 (50.0-81.3)	81.3 (59.4-93.8)	<.001
Marx activity level	8.0 (3.8-12.0)	9.0 (4.0-12.5)	.023

ACLR, anterior cruciate ligament reconstruction; IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; QOL, knee-related quality of life.

Multivariable modeling demonstrated the revision group to have a 7.8-point lower IKDC score (P < .001), a 3.2-point lower KOOS-Pain score (P = .012), a 10.4-lower KOOS-QOL score (P < .001), and a 2.0-point lower Marx score (P = .002) than the primary contralateral group, controlling for age, sex, body mass index, smoking status, degree of preoperative knee laxity, sport at initial injury, cartilage and meniscal status at primary ACLR, primary ACL graft type, and preoperative outcome score (Table 5).

Table 5

Estimated Patient-Reported Outcome Differences for Contralateral ACLR Relative to Revision ACLR 6 Years After Primary ACLR Adjusting for Potential Confounders ^a

	Rescaled Coefficient Estimate (95% CI)	P Value
IKDC	7.8 (4.3-11.3)	<.001
KOOS
Pain	3.2 (0.7-5.7)	.012
QOL	10.4 (4.6-15.1)	<.001
Marx activity level	2.0 (0.7-3.3)	.002

ACLR, anterior cruciate ligament reconstruction; IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; QOL, knee-related quality of life.

Discussion

The most important finding of this study is that patients who undergo revision ACLR within 5 years of primary ACLR report poorer PROMs than those who undergo a primary contralateral ACLR during that 5-year period. The noted differences in IKDC score, KOOS-QOL, and Marx activity level are large enough to be clinically relevant as well as statistically significant. Such differences in outcomes between the revision and contralateral ACLR groups suggest that the groups should not be pooled to study outcomes of ACLR despite the benefits of this methodology in regard to sample size.

The reasons why poorer PROMs are noted in the revision group are not entirely clear. One contributor is certainly the generally poorer outcomes of revision surgery. Multiple prior studies have demonstrated poorer outcomes of revision when compared with primary ACLR.^11,20,35 Patients undergoing revision surgery frequently have more substantial associated intra-articular damage and higher degrees of residual laxity.^20,35 Revision surgery also likely leads to much less symmetry in the lower extremities than bilateral primary ACLR. More asymmetrical lower extremity strength, particularly in the quadriceps muscle, has been associated with poorer knee function (PROMs) and potentially diminished articular cartilage integrity after ACLR.^2,14

A final potential contributor to divergent outcomes between these groups is the psychological effects of graft tear versus contralateral injury. While recent research has delved into the psychological effects of ACL injury and the impact of mental health on recovery,^3,33 little work has focused on the psychological impact of a graft tear versus a contralateral ACL injury. One could imagine that the effects on confidence in the reconstructed knee and fear of reinjury would vary greatly in these groups, but more research in this area is required.

This study has several important limitations that must be considered. First, the median follow-up from the most recent surgery (revision or primary contralateral ACLR) is relatively short at a median 4.4 years. This length of follow-up does not allow for the assessment of risk of osteoarthritis development or potential long-term differences between the groups. However, this time point was chosen to provide insight into patient function at this important time point for patients after ACLR. Furthermore, the minimum follow-up after this second surgery is only 1 year. One could consider limiting the minimum follow-up to 2 years, but data from the Scandinavian registries have demonstrated no difference in PROs between 12 and 24 months postoperatively.³¹ Therefore, injuries up to 5 years after primary ACL surgery were included (minimum, 1 year to final follow-up). In addition, given the sample size and length of follow-up, this study is underpowered to provide any insight into the risk of a further (third) ACL injury in these 2 groups. Strengths of the study include the prospective data collection, low loss to follow-up, and the inclusion of data from multiple surgeons via a variety of techniques, increasing generalizability.

Conclusion

Authors

MOON Knee Group

Annunziata (Ned) Amendola, MD (Duke University Sports Medicine, Durham, North Carolina, USA), Jack T. Andrish, MD (Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio, USA), Robert H. Brophy, MD (Washington University Sports Medicine, St Louis, Missouri, USA), Charles L. Cox, MD, MPH (Department of Orthopaedic Surgery, Vanderbilt University, Nashville, Tennessee, USA), David C. Flanigan, MD (Ohio State Sports Medicine, Columbus, Ohio, USA), Laura J. Huston, MS (Department of Orthopaedic Surgery, Vanderbilt University, Nashville, Tennessee, USA), Yuxuan Jin, MS (Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio, USA), Morgan H. Jones, MD, MPH (Department of Orthopaedic Surgery, Brigham and Women’s Hospital, Boston, Massachusetts, USA), Christopher C. Kaeding, MD, MPH (Ohio State Sports Medicine, Columbus, Ohio, USA), Robert G. Marx, MD, MSc (Hospital for Special Surgery Sports Medicine, New York, New York, USA), Matthew J. Matava, MD (Washington University Sports Medicine, St Louis, Missouri, USA), Eric C. McCarty, MD (Colorado University Sports Medicine, Boulder, Colorado, USA), Richard D. Parker, MD (Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio, USA), Emily K. Reinke, PhD (Duke University Sports Medicine, Durham, North Carolina, USA), Armando Vidal, MD (The Steadman Clinic, Vail, Colorado, USA), Michelle L. Wolcott, MD (Colorado University Sports Medicine, Boulder, Colorado, USA), Brian R. Wolf, MD, MS (University of Iowa Orthopedics and Rehabilitation, Iowa City, Iowa, USA), Rick W. Wright, MD (Department of Orthopaedic Surgery, Vanderbilt University, Nashville, Tennessee, USA).

Footnotes

Acknowledgements

Thank you, Jennifer Baldwin, for your publication assistance.

Submitted October 16, 2025; accepted January 3, 2026.

One or more of the authors has declared the following potential conflict of interest or source of funding: K.P.S. has received consulting fees from Novo Pedics, National Football League, Wake Forrest, and PRO-T; and is the Chair of the Publishing Advisory Board for AOSSM. Cleveland Clinic licensed Outcome Measurement and Evaluation (OME) technology used in this study to Oberd; K.P.S. is an inventor of the technology, and Cleveland Clinic is entitled to royalties from Oberd. K.P.S. has received grants from National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (AR075422, R01 AR074131, and AR053684). R.A.M. has received research funding from Moximed, Vericel, and Smith & Nephew. R.W.W. has received financial support from Hyalex Orthopaedics and Just Cause Apparel and stock and royalties from Responsive Arthroscopy and is on the board of relationship for AOSSM. M.J.M. has received consulting fees from Arthrex Inc; an unrestricted education grant for fellowship support from Breg Inc, Arthrex Inc, and Smith & Nephew Inc; and speaker fees from Elite Orthopedics. M.J.M. is also a board member for AOSSM. D.C.F. has received consulting fees from Smith & Nephew, Vericel, Moximed, J7J Sports, Hyalex, Anika, Arcuro, Nanochon, Conmed, and Medipost. M.H.J. has received consulting income from Grunenthal and Regeneron for scientific advisory and from the Journal of Bone and Joint Surgery for curriculum development; is an unpaid member of the editorial board of OJSM; and has received grant support to his institution from Pacira, Arthritis Foundation, and the National Institutes of Health. B.R.W. has received royalties and consulting fees from ConMed and is a member of the board of directors for AOSSM, American Board of Orthopaedic Surgery, and Mid-America Orthopaedic Association. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

ORCID iD

Kurt P. Spindler

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