BJSM - 2026-05-11 - Journal Article
Long-term risk of knee replacement after ACL reconstruction using the contralateral knee as an internal control: a National Hospital Episode Statistics database study of 135 881 patients.
Hennessy C, Murray J, Price AJ, Abram SG
Topics
Key Takeaway
At 20 years post-ACLr, the ipsilateral knee arthroplasty rate was 2.44% versus 0.88% in the contralateral knee, yielding an HR of 3.00 for isolated ACLr and 3.50 when concurrent meniscal surgery was performed.
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Summary
This study used National Hospital Episode Statistics data from England to estimate the relative risk of knee arthroplasty after ACLr by using each patient's contralateral, non-reconstructed knee as an internal control. At 20 years, ipsilateral arthroplasty rate was 2.44% versus 0.88% contralateral (HR 3.00 for isolated ACLr; HR 3.50 with concurrent meniscal surgery). The contralateral knee itself carried a slightly elevated arthroplasty rate compared to the background population, confirming that ACL-injured patients are not a representative baseline.
Key Limitation
The database captures only NHS-funded procedures in England, excluding private arthroplasty episodes, which likely underestimates the true arthroplasty rate in a cohort that skews toward younger, more active, and potentially higher-income patients who may preferentially use private care.
Original Abstract
OBJECTIVE
Estimate the population-specific relative risk of knee arthroplasty following anterior cruciate ligament (ACL) reconstruction (ACLr) in patients with a history of ACLr in only one knee.
METHODS
A population-based cohort of patients undergoing their first ACLr, with no previous or subsequent ACLr to their contralateral knee was extracted from National Hospital Episode Statistics data, England, UK (1997/1998-2022/2023). Mortality-adjusted Kaplan-Meier survival analysis (survival defined as not undergoing knee replacement) of the index knee undergoing ACLr versus the non-intervened knee. Subgroup analysis was done examining sex, age, index of multiple deprivation, ethnicity and whether ACLr was performed in isolation or with concurrent meniscal surgery. A comparison of the arthroplasty rate in both knees versus general population data was also performed.
RESULTS
135 881 ACLr patients were included. At 20 years post-ACLr, the rate of ipsilateral knee arthroplasty was 2.44% (95% CI 2.18% to 2.73%) versus the contralateral knee (0.88%, 95% CI 0.72% to 1.06%). The HR for knee arthroplasty versus the contralateral knee was 3.00 (95% CI 2.56 to 3.51) in isolated ACLr cases and 3.50 (95% CI 2.55 to 4.81) in cases with simultaneous meniscal surgery. In males, the HR was 3.27 (95% CI 2.72 to 3.92) versus the contralateral knee, and in females, the HR was 2.85 (95% CI 2.28 to 3.57) versus the contralateral knee. The increased HR of arthroplasty in the ACLr knee remained present across the different strata of index of multiple deprivation, ethnicity and age. The rate of arthroplasty was slightly higher in the contralateral (non-ACLr) knee when compared with the background population risk of knee arthroplasty.
CONCLUSIONS
This is the first study to estimate the population-specific relative risk of knee replacement following an ACL injury and reconstruction by using the contralateral knees of the same patients as the control. The relative risk is approximately three times that of the contralateral, uninjured knee. Our findings may better inform patients when discussing their long-term prognosis after ACL injury.