- Researchers investigated the long term risk of knee replacement surgery following anterior cruciate ligament reconstruction by comparing injured knees to uninjured contralateral knees.
- This population based cohort study analyzed 135,881 patients in England who underwent their first anterior cruciate ligament reconstruction between 1997 and 2023.
- At 20 years, the reconstructed knee had a 2.44 percent arthroplasty rate compared to 0.88 percent in the uninjured contralateral knee.
- The study found that anterior cruciate ligament reconstruction increases the hazard ratio for future knee replacement to 3.00 (95% CI 2.56 to 3.51).
- Clinicians can use these data to provide patients with specific prognostic information regarding the three fold increased risk of future joint replacement.
The Long-Term Articular Cost of Anterior Cruciate Ligament Injury
Anterior cruciate ligament injuries frequently lead to post-traumatic osteoarthritis, a condition that remains a primary cause of long-term disability despite surgical intervention [1]. While reconstruction aims to restore mechanical stability and facilitate a return to high-level activity, it does not entirely eliminate the risk of degenerative joint disease [2, 3]. Current evidence suggests that concomitant injuries to the meniscal or chondral surfaces significantly increase the odds of structural joint failure over time [2, 4]. Furthermore, the psychological and physical demands of returning to competitive sports can influence long-term joint health and the risk of secondary injuries [5, 6]. A comprehensive new study now utilizes a massive national database to quantify the specific risk of progressing to total knee arthroplasty by using the uninjured contralateral knee as a precise internal control.
A Large-Scale Internal Control Study Design
The primary objective of the study was to estimate the population-specific relative risk of knee arthroplasty following anterior cruciate ligament reconstruction (ACLr) in patients with a history of the procedure in only one knee. To provide a robust longitudinal perspective, the researchers extracted a population-based cohort from the National Hospital Episode Statistics data in England, United Kingdom, covering a 25 year period from 1997/1998 to 2022/2023. This extensive dataset included 135,881 patients undergoing their first ACLr who had no record of previous or subsequent reconstruction in their contralateral knee. By isolating patients with unilateral surgery, the authors sought to clarify the long-term articular consequences of the initial injury and subsequent surgical intervention.
The researchers utilized the patient's own non-intervened contralateral knee as an internal control, a design choice that accounts for individual-specific variables such as genetic predisposition to osteoarthritis, activity levels, and systemic health. To analyze the data, the team employed a mortality-adjusted Kaplan-Meier survival analysis, which is a statistical method used to estimate the probability of an event occurring over time while accounting for patients who die during the follow-up period. In this specific model, survival was defined as not undergoing knee replacement. This methodology allowed for a direct comparison between the index knee undergoing ACLr and the healthy contralateral limb, providing a precise measure of how much the reconstructed knee's trajectory deviated from the patient's own baseline joint health.
Quantifying the 20-Year Arthroplasty Hazard
The longitudinal data reveals a clear divergence in joint survival between the reconstructed and uninjured limbs over two decades. At 20 years post-ACLr, the rate of ipsilateral knee arthroplasty was 2.44% (95% CI 2.18% to 2.73%), representing the absolute risk of requiring a total joint replacement in the surgically treated knee. In contrast, the rate of contralateral knee arthroplasty was 0.88% (95% CI 0.72% to 1.06%) during the same period. These figures provide clinicians with concrete benchmarks for patient counseling regarding the long-term prognosis of the joint following ligamentous reconstruction, moving beyond subjective assessments of joint stability to objective measures of end-stage joint failure.
When analyzing the risk of joint failure, the researchers calculated the Hazard Ratio (HR), which is a measure of how much more likely an event is to happen in one group compared to another over a specific time interval. For patients who underwent isolated ACLr cases, the HR for knee arthroplasty versus the contralateral knee was 3.00 (95% CI 2.56 to 3.51). This indicates that the relative risk of knee replacement following ACLr is approximately three times that of the contralateral, uninjured knee. This threefold increase in risk underscores the persistent vulnerability of the reconstructed joint, even in the absence of concomitant meniscal or chondral pathology, and suggests that the initial trauma or the surgical intervention itself significantly alters the joint's degenerative trajectory.
Beyond the direct comparison between limbs, the study also evaluated how these patients compare to the broader community. Interestingly, the rate of arthroplasty was slightly higher in the contralateral (non-ACLr) knee when compared with the background population risk of knee arthroplasty. This finding suggests that patients who sustain an anterior cruciate ligament injury may possess systemic or behavioral risk factors, such as genetic predispositions to osteoarthritis or higher baseline activity levels, that elevate their risk for joint replacement in both knees relative to the general population. For the practicing physician, this highlights the importance of monitoring the health of the uninjured limb as well as the reconstructed one.
The Compounding Impact of Meniscal Injury and Demographics
The risk of end-stage joint failure is significantly influenced by the presence of concomitant intra-articular pathology at the time of reconstruction. While isolated ligamentous repair carries a substantial risk, the researchers found that the hazard increases when the meniscus is also involved. Specifically, the Hazard Ratio for knee arthroplasty versus the contralateral knee was 3.50 (95% CI 2.55 to 4.81) in cases with simultaneous meniscal surgery. This elevation from the baseline risk of isolated reconstruction suggests that the combined mechanical and biological insult of a meniscal tear and subsequent surgical intervention further accelerates the degenerative process. To ensure the findings were robust across different patient profiles, the subgroup analysis examined sex, age, index of multiple deprivation (a measure of regional socioeconomic status), ethnicity, and whether the procedure was performed in isolation or with concurrent meniscal surgery.
Demographic factors also revealed distinct patterns in joint survival, though the increased risk remained a universal finding across all studied populations. When stratified by sex, the data showed that in males, the Hazard Ratio for knee arthroplasty was 3.27 (95% CI 2.72 to 3.92) versus the contralateral knee. This was slightly higher than the risk observed in the female cohort, where in females, the Hazard Ratio for knee arthroplasty was 2.85 (95% CI 2.28 to 3.57) versus the contralateral knee. Despite these minor variations between sexes, the increased Hazard Ratio of arthroplasty in the reconstructed knee remained present across different strata of index of multiple deprivation, ethnicity, and age. Furthermore, when the researchers compared the arthroplasty rates in both knees against general population data, they confirmed that the surgical limb's risk profile is uniquely elevated even when accounting for broader community trends. For the clinician, these results indicate that the long-term risk of joint replacement is a consistent concern for all patients following reconstruction, regardless of their demographic background.
References
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2. Whittaker JL, Losciale JM, Juhl CB, et al. Risk factors for knee osteoarthritis after traumatic knee injury: a systematic review and meta-analysis of randomised controlled trials and cohort studies for the OPTIKNEE Consensus. British Journal of Sports Medicine. 2022. doi:10.1136/bjsports-2022-105496
3. Filbay SR, Bullock G, Russell S, Brown F, Hui W, Egerton T. 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 (Auckland, N.Z.). 2025. doi:10.1007/s40279-025-02268-5
4. Øiestad BE, Engebretsen L, Storheim K, Risberg MA. Winner of the 2008 Systematic Review Competition: Knee Osteoarthritis after Anterior Cruciate Ligament Injury. The American Journal of Sports Medicine. 2009. doi:10.1177/0363546509338827
5. 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. doi:10.1136/bjsports-2013-093398
6. Ardern CL, Webster KE, Taylor NF, Feller JA. Return to sport following anterior cruciate ligament reconstruction surgery: a systematic review and meta-analysis of the state of play. British Journal of Sports Medicine. 2011. doi:10.1136/bjsm.2010.076364