Knee Arthroscopy, Knee Arthroplasty, Foot & Ankle Surgery - Rates of Surgery, Outcomes, Complications, Variation

This Data Sharing Agreement permits the University of Oxford to retain and process the data for the duration of the Agreement. Permission to retain the data for an interim period is a practical step to enable the data recipient to comply with the necessary requirements in order to secure a longer-term Data Sharing Agreement permitting further retention and reuse of the data for approved purposes.

The following information provides background information on the purpose of the original study:

The University of Oxford’s Big Health Data Group (BHDG) requires HES and linked mortality data for the purpose of a project studying knee arthroscopy and knee arthroplasty surgery. The study will be performed by employees of the University of Oxford at the Botnar Research Centre, Nuffield Department of Orthopaedic, Rheumatology & Musculoskeletal Science (NDORMS).

The project will investigate trends in surgery (arthroscopy and knee replacement), variation in practice (over 20 years; by geographic region), and the outcomes and complications and service use (including length of stay) of this type of surgery and factors that may be associated with these (including patient frailty, comorbidity, diabetes, obesity, infections, previous surgery and medical conditions, age, gender, demographics).

This work is research in the public interest as it aims to improve care for all patients considering undergoing this type of process – informing clinicians and commissioners of variation and outcomes and complications to support work to improve and standardise treatment selection choices.

The University of Oxford has determined that there are no moral or ethical issues from dissemination of data for this purpose. Once received from NHS Digital, the data being processed by the University of Oxford will be pseudonymised and will be compliant with the ICO's "Anonymisation: managing data protection risk" code of practice.

A long-term cohort of patients who underwent knee arthroscopy and/or knee replacement (primary and revision) is required to investigate trends and variation over twenty-years and to investigate responses to the publication of evidence over this period. These data will also allow precise determination of the rate of complications and to control for confounding variables (such as age, gender, comorbidity, deprivation, ethnicity) when investigation associations between treatment and patients factors and outcome and complications.

This work is part of a general project to improve orthopaedic treatment selection, reduce variation, and improve outcomes. It is funded, in part, by National Institute for Health Research (NIHR DRF-10-030-2017) and by a grant from the NHS Getting It Right First Time (GIRFT) programme. Neither funder will be involved in the data processing or interpretation of this project. The project involves two work packages which are described below.

The data subjects are all patients who have had knee arthroscopy or total knee replacement identified from their hospital episodes data (HES). The University of Oxford requires details of all hospital episodes for these patients as the study will explore potential links between surgery and subsequent health issues that are not necessarily specific to the knee (e.g. venous thromboembolism, stroke, heart attack, hospital acquired infection). Data on patients with a diagnosis (ICD-10) of osteoarthritis, meniscal tear or knee ligament rupture is required to analyse the overall rate of surgery in these groups and rate of complications in matched groups undergoing or not undergoing surgery where possible.

Work Package #1:

The first work package aims to inform on the complications, short and long-term outcome of knee arthroscopy surgery (all sub-types of knee arthroscopy and all indications). Knee arthroscopy is a very commonly performed procedure and around 150,000 knee arthroscopies are performed in England every year. Despite the frequency with which the procedure is performed, data on the risks and complications associated with the procedure is limited.

In relatively small cohort studies, arthroscopic surgical procedures such as meniscectomy and anterior cruciate ligament (ACL) reconstruction have been shown to be associated with the subsequent development of osteoarthritis. There is also high-level evidence to suggest that many arthroscopic procedures (such as knee washout and meniscectomy) are ineffective if performed on patients with osteoarthritis. These patients may be more appropriately managed with other interventions such as physiotherapy or knee replacement.

Data demonstrates the number of knee arthroscopies performed each year is rising, especially in older age groups and a key objective of the proposal is to investigate the historical trends in arthroscopy practice and the factors underlying this. It is highly likely that knee arthroscopy is being over-performed. This study proposes to determine the rate of complications (such a venous thromboembolism, stroke, heart attack, death) that occurs following knee arthroscopy. The study also proposes to investigate the association of the procedure with a diagnosis of osteoarthritis and with further procedures such as repeat arthroscopy or knee replacement. For patients subsequently undergoing knee replacement the study wishes to determine if previous knee arthroscopy is associated with any subsequent complications. The study will compare patients undergoing early joint replacement after arthroscopy (e.g. within 90 days) to those undergoing later joint replacement (e.g. after 2 years). Other short-, medium-, and long-term outcomes will be analysed, including further procedure such as knee alignment surgery (e.g. osteotomy) which may be performed for early osteoarthritis. In reviewing patients undergoing ligament reconstruction, the study team will analyse difference age groups separately. For example, outcomes of ligament reconstruction in the paediatric population (<18 years) are poorly defined and surgery in this group may result in impairment to growth and a need for further surgical procedure which will be evaluated. For this the study the University of Oxford require all inpatient and Civil Registration data for all knee replacement (total or uni-compartment) patients.

The role of arthroscopic treatment in the management of early osteoarthritis has been highlighted as a Top 10 research priority in the recently published James Lind Alliance (JLA) Priority Setting Partnership on Early Osteoarthritis. The James Lind Alliance (JLA) is a non-profit making NIHR supported initiative which brings patients, carers and clinicians together in Priority Setting Partnerships (PSPs) to identify and prioritise the Top 10 uncertainties, or 'unanswered questions', about the effects of treatments that they agree are most important.

The study will also investigate the number of cases being performed in patients with osteoarthritis – a group that evidence suggests are less likely to benefit from arthroscopy – but investigating the association with total knee replacement. Finally, the study will report in detail on the trends in rates of knee arthroscopic procedures and how these have varied over time along with geographic variation.

The data years requested are required for the analysis of the following: trends in the rates of certain procedures (e.g. with publication of evidence) and coding of index procedures, trends in the rates of complications (and changes with changing practice), and trends in associations between procedures – such as knee arthroscopy followed by total knee replacement. This information will be of value to patients, the public and to health care professionals: informing on the pictures of changing surgical practice, the risks of current practice with comparison to previous practice and a review of how practice has changed in response to the publication of guidelines (for example, from the National Institute for Health and Care Excellence, NICE).

The study has minimised the data requested during the time-period as much as possible by limiting to defined OPCS index procedure codes and specific ICD-10 codes (osteoarthritis, meniscal tears, ligament rupture). It is not possible to reduce the data further without compromising the ability to analyse trends in complications and associations between knee arthroscopy and knee replacement which is a key output of the project.

Surgical practice has changed considerably over the time-period requested – for example, reduced rates of knee ‘washout’ (e.g. OPCS W852, often performed to treat osteoarthritis in the 1990s) but increased rates of ‘meniscectomy’ (e.g. W822) beyond 2002. It is important to explore the demographics and population rates of these procedures and to investigate factors underlying these changes. There is the possibility that patients with osteoarthritis previously underwent washout but may now be undergoing a meniscal procedure – and therefore subsequently being at high risk of requiring a total knee replacement soon afterwards. The association between changing practice such as this and complications and repeat surgery rates is currently unknown and would benefit health care practice. Much of the evidence against knee washout was published around 1999-2002 and therefore this data period is required to investigate treatment practice before publication of this evidence, the transition period include the rate of change in practice, and the subsequent period which seems to include some increase in the rate of alternative surgical procedures for the degenerative knee with osteoarthritis.

Other past trends of interest include the rate of cruciate ligament reconstruction and developing osteoarthritis or requiring total knee replacement. The delay between ligament injury, reconstructive surgery, and development of symptomatic osteoarthritis could easily be 15-20+ years and this period of data follow up is therefore required to investigate time to a diagnosis of osteoarthritis and time to total knee replacement. The association of meniscal surgery with a diagnosis of osteoarthritis and requiring total knee replacement later in life will also be explored.

Work Package #2:

A second work package will investigate the outcomes of knee replacement surgery (primary or revision knee replacement) in isolation – separate from the arthroscopy analysis work. There is a need to better understand the factors that determine outcomes in knee replacement – such as patient frailty, comorbidity, and previous surgical procedures. Performing knee replacement as a ‘day case’ procedure is becoming more common but the proportion of patients eligible for this intervention is unknown and, for patients currently undergoing day case knee replacement, the outcomes in comparison to those with a conventional length of stay is unknown. National lengths of stay will be analysed and in units/regions practicing day case knee replacement, the outcomes (e.g. complications, infection, readmission, reoperation, revision) of these patients in comparison to conventional lengths of stay will be compared. Additionally, outcome of revision knee surgery will be investigated according to the indication for revision and previous knee replacement (e.g. is the outcome of a revision knee procedure better for certain types of primary knee replacement (e.g. partial knee replacement) or following certain indications. For example, the rate and outcomes of patients sustaining a fracture (“peri-prosthetic fracture” indication) to a previous knee replacement will be determined and the rate and outcomes of patients sustaining an (“prosthetic joint infection”) to a previous knee replacement will be determined and compared to those without these indications. In addition to exploring patient and implant factors, we shall explore how the delivery of care, such as time elapsed from admission to surgery, affects outcomes. The cost-effectiveness (health economics) of different treatment approaches for knee replacement will be investigated using cost-data in the hospital episode statistics including the impact from length of stay, complications, readmission, reoperation. We will also stratify outcomes for primary knee, revision knee or re-revision knee arthroplasty cases. Patients undergoing bilateral (both side) knee replacement will be compared to single side (and delayed bilateral versus simultaneous bilateral). Overall rates of complications and reoperations (such as manipulation under anaesthetic or revision surgery) will be investigated for all patients undergoing knee replacement and stratified by type of intervention, indication, and patient factors.

Finally, the association between bariatric (weight loss) surgery and knee replacement outcomes will be studied to evaluate the potential of bariatric surgery as a staged intervention in obese individuals with knee osteoarthritis (OA) who require knee replacement. Obesity represents a considerable and increasing burden to global healthcare systems. Obesity is common in patients undergoing knee replacement and it not only greatly increases the risk of osteoarthritis (OA) development but is associated with an increased risk of postoperative complications and early prosthesis failure. Furthermore, it has been demonstrated that whilst mobility improves after knee replacement, this does not lead to a postoperative reduction in obesity or associated comorbidities. Whilst weight reduction is promoted prior to TKR in England, current approaches are reported to be relatively ineffective, in part due to patients’ reduced ability to exercise due to knee pain. Bariatric surgery is recognised as the most effective treatment achieving significant and durable weight loss. It is a cost-effective approach to obesity management compared to non-surgical interventions, with an incremental cost effectiveness ratio of £2000-£4000 per QALY over 20 years. Additionally, long-term benefits after bariatric surgery compared to lifestyle intervention and intensive medical therapy have been established in obesity-associated metabolic diseases such as Type 2 diabetes. For this reason, in obese individuals with diabetes, the incremental cost-effective ratio for bariatric surgery falls to £1367 per QALY. It is hoped that bariatric surgery in obese individuals that require total knee replacement TKR will improve both knee-related and metabolic health outcomes and thereby represent a highly cost-effective intervention in this group. Patient undergoing bariatric surgery before or after knee replacement will be identified. The rate of knee replacement in patients with diagnosed osteoarthritis will be compared between those undergoing bariatric surgery and those not undergoing this invention. The relative outcomes (complications, readmission, reoperation, length of stay) of the knee replacement bariatric surgery will be investigated.

The University of Oxford is the sole data controller and data processor of the data supplied by NHS Digital under this Agreement. NIHR and GIRFT are funding the work of the department and in return expect the department to undertake research such as this but neither body can access data nor has a role in analysis or interpretation.

Under this Agreement, the data may be retained and processed by the University of Oxford for the purposes of original study but no new data will be provided by NHS Digital.

The following provides background on the processing activities undertaken for the original study:

Under a previous iteration of this Agreement, NHS Digital supplied HES data from 1997/98 to 2016/17 and linked mortality data for patients who experience knee arthroscopy or total knee replacement surgery identified by specific OPCS codes. This data was provided for the purpose of work package #1.

All data under considered to be a special category of personal data (‘concerning health’). The data is pseudonymised.

This Agreement amends the previous Agreement to permit the use of the data for work package #2 in addition to work package #1.

The datasets will be held on a password protected and encrypted drives at the Botnar Research Centre, Nuffield Department of Orthopaedic, Rheumatology & Musculoskeletal Science (NDORMS). There are no subsequent flows of the data.

Access to the data will be restricted to members of the research team employed by the University of Oxford who are specifically assigned to work on this study. The data will be used exclusively for the purposes of the specified study. The data will not be made accessible to any third parties. At the end of the study, the data will be safely held on a password protected and encrypted drive at the Botnar Research Centre, for further 5 years, and accessed only to answer questions arising from the publication and other publicity if required.

Simple descriptive statistics will be used to report trends in the rate of arthroscopic, knee replacement and bariatric surgery, the co-occurence of these interventions and overall rates of complications in obese and in non-obese patients. When more than one of these operations are performed, the time between interventions will be described. Regression analysis will be used to identify predictors of complications (e.g. venous thromboembolism) or further surgery (e.g. knee replacement). The development of metabolic comorbidities (such as type 2 diabetes, cardiovascular disease and non-alcoholic fatty liver disease) in obese patients who have had bariatric surgery may be compared to those who have not.

The data on all knee replacements will be used to compare the outcome of patients previously undergoing knee arthroscopy. It will also be used to compare the post-knee replacement outcomes (including length of stay on TKR admission, readmission rate, revisional knee surgery rate) irrespective of a history of knee arthroscopy. Outcomes of all knee replacements (partial, total, revision) will be investigated (including adverse outcomes, length of stay, readmission, reoperation) irrespective of any history of knee arthroscopy, and the impact of previous procedures and comorbidities determined. These groups will be carefully matched for any potentially confounding factors. Missing data will be handled using multiple imputation methods if indicated. Geographical Information Systems will be used to produce maps depicting regional variation in rates of intervention or outcome, including in different sub-populations (e.g. patients with osteoarthritis, bariatric surgery, comorbidity groups) and to depict any variation in the rate of complications and further surgery, when considered appropriate.

Desensitised extracts will be created by removing all Civil Registration data variables, replaced by flag variables or time to event variables. Specifically:

- New optional variable 1: Died? = 0/1

- New optional variable 2: Flag for death within 30 days, 90 days, 1 year, (then annual to end of follow up period)

- New optional variable 3: Days to death (Any dataset with this variable will have all other date fields reduced to year and month level of detail to prevent backwards calculation of exact date of death – in these cases, the encrypted HESID and epikey variables will also be replaced with new random variables to prevent subsequent linkage to any extract with full dates).

All desensitised extracts will be managed according to the same IG guidelines of the BHDG and will only be accessed by University of Oxford researchers for the purposes described in this Agreement.

The data will not be linked or matched with any other data.

There will be no requirement nor attempt to re-identify individuals.

Data processing will only be carried out by substantive employees of the University of Oxford who have been appropriately trained in data protection and confidentiality

The main output of this study will be a summary of post-operative complications of knee arthroscopy in the short and long term. Independent predictors of complications and repeat surgery such as knee replacement will be identified from the results of the regression model. Outcomes of knee replacement after knee arthroscopy will be compared to those without prior knee arthroscopy. Association of knee arthroscopy with a ICD-10 diagnosis of osteoarthritis will be investigated and analysed in context of any subsequent knee replacement. The outcomes of ligament reconstruction (complication, reoperation, later surgery such as knee replacement) will be investigated and differences in outcome by age-group (including paediatric population) reported. Additionally, the interaction between obesity surgery and orthopaedic pathways in obese patients with osteoarthritis will be assessed. The association between previous bariatric surgery and post-Total Knee Replacement (TKR) outcomes in individuals with previous diagnoses of OA and obesity will be defined. The length of stay and outcomes of knee replacement patients will be reported and the factors associated with these determined. Day case knee replacement practice, regional variation, outcomes will be reported and the potential impact from any change in practice reported.

Based on the findings of the study, a scientific paper will be written for submission to high quality peer-reviewed journals (for example, previous work from the group has been published in the BMJ, The Lancet). The study also aims to present findings to professionals at conferences and meetings.

The specific UK conferences to submit findings of this research to are: the British Orthopaedic Association (BOA) and the British Association for Surgery of Knee (BASK). The data related to bariatric surgery may be presented at the British Obesity and Metabolic Surgery Society’s Annual Meeting. International dissemination will also be sought, through journal publication and conferences such as the American Academy of Orthopaedic Surgeons (AAOS), European Federation of National Associations of Orthopaedics and Traumatology (EFORT) and the International Federation for the Surgery of Obesity’s Annual Congress.

The study will develop Plain English summaries of findings for communication to patients and members of the public - these will be freely available and published on the NDORMS website (ndorms.ox.ac.uk). The findings may also be presented at established patient and public engagement events. The proposed analysis plan and outputs has been reviewed and approved by an established patient and public involvement (PPI) group.

All outputs will adhere to the HES analysis guide so that data is only shown in aggregate form with small numbers suppressed.

The target date for just the publications is 18-months following receipt of the data.

Key project outputs:

1. The rate of serious complications following knee arthroscopy (including comparison of groups by diagnosis and the arthroscopic procedure performed).

2. The rate of knee arthroscopy in patients with osteoarthritis / ligament rupture / meniscal tears.

3. The rate of progression to osteoarthritis in patients without osteoarthritis (e.g. after arthroscopy; after diagnosis of ligament rupture; after ligament reconstruction; after diagnosis of meniscal tear).

4. The rate of knee replacement surgery after knee arthroscopy (and time points).

5. The outcomes and complications of knee replacement and predictors (e.g. may include: previous arthroscopy, previous bariatric surgery, type of previous primary knee replacement for revision cases, age-group, frailty, previous medical diagnoses and complications, impact from periprosthetic fracture, comparison to approaches to bilateral surgery)

6. Trends in the rates of procedures (historical trends and factors underlying this)

7. Geographic variation in the rates of arthroscopic procedures and associated knee replacement procedures. All outputs will be controlled for factors such as patient demographic, co-morbidity, and other surgical procedures with regression analysis.

8. The rate of complications and revisional knee surgery in obese individuals and in individuals who have previously had bariatric surgery after TKR.

9. Trends in the rates and timing of bariatric surgery in obese patients having TKR for osteoarthritis.

10. Incidence of new obesity-related comorbidities in obese individuals and in individuals who have previously had bariatric surgery after TKR.

11. Proportion and variation of patients undergoing day-case knee replacement, potential number of eligible patients, differences in outcomes and complications between groups.

12. Outcomes and complications of primary and revision knee replacement (e.g. reoperation such as manipulation under anaesthetic and revision, medical adverse outcomes, readmission).

The dissemination of the findings of this study is intended to benefit health care by rigorously reporting the rate of complications and outcome of knee arthroscopy. It is highly likely that for many patients currently undergoing knee arthroscopy, the procedure may not be beneficial – for example, when performed on a background of advanced osteoarthritis. It is important to investigate the association of knee arthroscopy procedures with a diagnosis of osteoarthritis and knee replacement surgery, complications and outcome of any subsequent knee replacement.

The study aims to improve health practice, reducing rates of unnecessary surgery by disseminating findings on the rate of complications of the procedure in different populations of patients and will determine predictors of outcome through multiple variable regression analysis.

Trends in the rate of surgery in groups of patients categorised by age and diagnosis of osteoarthritis will be determined and highlighted. Geographic variation will also be determined and publicised.

The study will provide evidence on identifying patients who are highly likely to progress to require a joint replacement at an early stage and determine if the outcome of their knee replacement may be compromised by the prior knee arthroscopy.

The information will inform patients and surgeons and the aim is to improve health practice and reduce rates of knee arthroscopy when this is unlikely to be beneficial. The study outputs will also inform NHS managers, commissioners and other health professionals of the outcomes and predictors of outcome of knee arthroscopy. This will encourage a change in practice where necessary, for example due to geographic variation or inappropriately high rates of surgery for patients with osteoarthritis. The study outputs may provide commissioners with evidence of any factors that can explain unwarranted geographical variation in knee arthroscopy surgery.

Outcomes in different groups of patients undergoing ligament reconstruction and knee replacement may inform practice – for example, a change in practice in the timing and age of ligament reconstruction or an increase in the rate of day-case knee replacement nationally.

Additionally, it will be determined whether bariatric surgery in obese individuals prior to TKR surgery is associated with a reduction in post-TKR complications, revisional knee surgery and new incidence of obesity-associated comorbidities. Geographic variations in current practice will also be identified. It is anticipated that this will inform the future treatment of obese individuals with osteoarthritis and be of interest to health professionals managing this condition.

The target date is 24-48 months following receipt of the data (for complete project).

The study aims to improve health practice, reducing rates of unnecessary surgery by disseminating findings on the rate of complications of the procedure in different populations of patients. We will determine predictors of outcome through multiple variable regression analysis.

Trends in the rate of surgery in groups of patients categorised by age and diagnosis of osteoarthritis will be determined and highlighted. Geographic variation will also be determined and publicised for both knee surgery and foot and ankle surgery interventions with comparisons made where appropriate.

The study will provide evidence on identifying patients who are highly likely to progress to require a joint replacement at an early stage and determine if the outcome of their knee replacement may be compromised by the prior knee arthroscopy.

The information will inform patients and surgeons and the aim is to improve health practice and reduce rates of procedure which are unlikely to beneficial or where associated with a higher rate of adverse outcomes. The study outputs will also inform NHS managers, commissioners and other health professionals of the outcomes and predictors of outcome of knee arthroscopy. This will encourage a change in practice where necessary, for example due to geographic variation or inappropriately high rates of surgery for patients with osteoarthritis. The study outputs may provide commissioners with evidence of any factors that can explain unwarranted geographical variation in knee arthroscopy surgery.

Outcomes in different groups of patients undergoing knee, foot, ankle surgery may inform practice – for example, a change in practice in the timing and age of undergoing a surgical procedure or an increase in the rate of day-case surgery nationally.

It will be determined whether bariatric surgery in obese individuals prior to TKR surgery is associated with a reduction in post-TKR complications, revisional knee surgery and new incidence of obesity-associated comorbidities. Geographic variations in current practice will also be identified. We anticipate that this will inform the future treatment of obese individuals with osteoarthritis and be of interest to health professionals managing this condition.

Adverse outcomes following elective foot and ankle surgery will be determined and reported, for example comparing outcomes of ankle replacement and ankle arthrodesis – two procedures which can be offered for similar indications and where patient information on the relative benefits and risks are limited. Similar information will be reported for the other commonly performed procedures in knee, foot and ankle surgeons including arthroscopy and reconstruction.

The target date is 24-48 months following receipt of the data.

Several Journal articles have been published, this research has produced findings that may be used to benefit health and social care in England. For example:

• The consequences of septic knee arthritis in patients undergoing arthroscopic knee washout are serious. These findings highlight the potentially devastating outcomes associated with sepsis from musculoskeletal joint infection.

• Rates of paediatric and adolescent ACL reconstruction have increased 29-fold over the last 20 years. Despite the increasing rate in the younger population, the risk of serious complications, including further surgery for growth disturbance is very low. The results of our study provide a point of reference for shared decision making in the management of ACL injury in the paediatric and adolescent population.

• The overall risk of adverse events after ACL reconstruction is low; however, some rare but serious complications, including infections or pulmonary embolism, may occur. Around 3% of patients undergo further ipsilateral or contralateral ACL reconstruction within 5 years. These data will inform shared decision making between clinicians and patients considering their treatment options.

• Patients developing a meniscal tear undergoing APM are at greater risk of knee arthroplasty than the general population. This risk is three-times greater in the patient's affected knee than in the contralateral knee. Women in the cohort were at double the risk of progressing to knee arthroplasty compared with men. These important new reference data will inform shared decision making and enhance approaches to treatment, prevention, and clinical surveillance.

• Patients sustaining an ACL injury who undergo ACLr are at elevated risk of subsequent knee arthroplasty in comparison with the general population. Although the absolute rate of arthroplasty is low, the risk of arthroplasty at a younger age is particularly elevated. When the outcome of shared decision-making is ACLr, this data will help inform patients and clinicians about the long-term risk of requiring knee arthroplasty.

• Over the study period, the proportion of patients undergoing arthroplasty within one-year of APM increased. In 2015-16, of patients aged 60 years or older who underwent APM, 10% subsequently underwent knee arthroplasty within one year (17% within two years in 2014-15) and there was a high level of regional variation in this outcome. The development and adoption of national treatment guidance is recommended to improve and standardise treatment selection.

• The 2018 BASK Arthroscopic Meniscal Surgery Treatment Guidance will facilitate the consistent identification and treatment of patients with meniscal lesions. It is hoped that this guidance will be adopted nationally by surgeons and help inform healthcare commissioning guidance. Validation in clinical practice is now required and several areas of uncertainty in relation to treatment should be a priority for future high-quality prospective studies.

• Overall, the risk associated with undergoing arthroscopic partial meniscectomy was low. However, some rare but serious complications (including pulmonary embolism and infection) are associated with the procedure, and the risks have not fallen with time. In view of uncertainty about the effectiveness of arthroscopic partial meniscectomy, an appreciation of relative risks is crucial for patients and clinicians. Our data provide a basis for decision making and consent.

• The rate of ACL reconstruction (12-fold) and MR (2.4-fold) has increased in England over the last two decades. There is variation in these rates across geographical regions and further work is required to deliver standardised treatment guidance for appropriate use.

• Over the last 20 years, and likely in response to new evidence, rates of arthroscopic knee washout and diagnostic arthroscopy have declined by up to 90%. APM rates increased about 130% overall but have declined recently. Rates of chondroplasty increased about 15-fold. There is significant variation in practice, but the appropriate population intervention rate for these procedures remains unknown.

• The agreed terminology will enable patients with meniscal lesions to be identified and stratified consistently in clinical practice, research and guideline development.