Introduction

Traumatic knee injuries are very common, occurring in 720–1800 per 100 000 persons annually.1 2 Injury frequency varies by sex/gender, age and precipitating event, with the highest incidence in adolescents and young adults3 participating in sport and recreational activities.4 5 Traumatic knee injuries are associated with short-term (eg, negative mood states, re-injury anxiety, loss of social identity,6 withdrawal from sport,7 physical inactivity8 9 and long-term (eg, obesity,10 reduced quality of life11 12 and osteoarthritis (OA)13) negative health outcomes. Specifically, these injuries are linked to a 6-fold increased risk of radiographic OA at 11 years,14 and 6-fold elevated lifetime risk of arthroplasty.15 16 Due to their relatively young injury age, people with traumatic knee injuries develop OA at an earlier age than to those without injuries, leading to more years lived with disability.17

Knowing that traumatic injuries precipitate knee OA presents an opportunity to prevent (delay or halt) OA. This opportunity hinges on knowing who develops post-traumatic OA (PTOA; target population), when and how to intervene (target treatments), and what are the most important outcomes and methods to assess them.18

No clinical recommendations are available to guide interventions that might prevent symptomatic PTOA. Care pathways for people with knee injuries vary widely by practitioner, setting, diagnostic testing completed, surgery(s) performed, length/content of care and payment model.19 Importantly, people at-risk of PTOA rarely seek or receive care promoting risk awareness or knee health.20–22 From a research perspective, heterogeneity in OA definitions, outcome domains and measures, prevents synthesis of results across the field.23 24

OPTIKNEE is an international group of clinician scientists, scientists, and patient and clinician partners working to optimise knee and overall health after a traumatic injury to prevent symptomatic knee PTOA. After multiple planning meetings (2017–2019) and a priority setting exercise in 2019 (Toronto, Canada), the OPTIKNEE group embarked on a consensus process. This paper reports the consensus process and its results: definitions and recommendations to guide clinical rehabilitation practice and research aimed at informing, developing, evaluating and implementing rehabilitation interventions to improve knee and overall health-related outcomes following a traumatic knee injury.

MethodsDesign and reporting

The OPTIKNEE consensus followed a seven-step hybrid approach guided by the RAND UCLA Appropriateness Method (RAM)25 and Nominal Group Technique26 (figure 1). The RAM is an established approach explicitly developed to leverage expert opinion in situations where evidence may be incomplete, while the Nominal Group Technique provides a structured approach to face-to-face meetings to facilitate widespread engagement of all participants. Reporting was informed by the Appraisal of Guidelines for Research and Evaluation statement (AGREE II)27 and Conducting and REporting of DElphi Studies28 as appropriate. Box 1 outlines the methods for each consensus step including expert group selection. All systematic review protocols and consensus materials are freely available on the Open Science Framework at https://osf.io/7tfxn/.

Box 1 Consensus methods

Convene steering committee (September 2019)

Steering committee convened after a 2019 priority setting exercise* hosted by JLW, EMR and KMC.

Members included a balance of early (JLW and AGC) and later career (EMR and KMC) clinician scientists, from 3 continents, with expertise in knee injury and OA who had undertaken groundwork for the consensus since 2016.

One committee member specifically recruited for expertise in evidence synthesis (CBJ).

Develop guiding questions (September 2019)

Convene Expert group (October–December 2019)

6 experts (CAE, SF, MAR, BEØ, EMM and MvM) were asked to co-lead a systematic review related to a guiding question (review leads).

Review leads identified other experts for their review teams, including as possible, a patient and a clinician partner.

Equity, Diversity and Inclusion: Experts were selected on their research activities related to traumatic knee injury and PTOA. Gender equity and diversity of career stage, race and geographical location was sought. Clinical rehabilitation experience in the field was viewed favourably.

Evidence synthesis to address guiding questions (August 2020–November 2021)

Single systematic reviews were conducted to address the burden, risk factor and PROs questions, while the intervention and functional outcomes questions were addressed in two reviews each.

Review protocols were registered on the Open Science Framework† (7 August 2020). The Cochrane Handbook1 informed conduct, and the PRISMA guidelines2 and PRISMA-Search extension,3 informed reporting.

Search strategies developed with a librarian scientist, consistent across the population construct (traumatic knee injury and mean or median injury age ≤30 years)‡. All reviews, except the risk factor review, focused on ACL and/or meniscal tears to reflect the majority of evidence. For the risk factor review, the population was expanded to evaluate PTOA risk across all knee injury types.

Risk-of-bias across included studies was assessed, and when appropriate, certainty of evidence rated.

Table 1 summarises review topics, objectives, synthesis type, risk-of-bias tools and certainty of evidence approach for each review.

Steering committee members and review leads met (video conferencing§) every 4-6 weeks (~1 hour) over the review protocol development and conduct stage to ensure consistency in conduct, provide methodological support, and navigate barriers encountered.

Generate consensus recommendations (November–December 2021)

Consensus recommendations were generated through an iterative process.

Review groups submitted clinical recommendations and research recommendations, each accompanied by a statement of supporting evidence.

Steering committee members reviewed recommendations, and when needed, requested additional recommendations based on other evidence sources including other systematic reviews, expert consensus, high quality original studies and/or expert opinion.

Clarity of draft recommendations were discussed during a videoconferencing meeting with review leads, refined and finalised¶. Draft definitions for commonly used terms across the recommendations were developed by the steering committee to ensure consistency and to facilitate discussions.¶

Revise recommendations (January–May 2022)

Draft definitions and recommendations were discussed during 6, 2-hour videoconferencing sessions and revised for voting.**

Before meetings, expert group members reviewed the intent of the definitions or recommendations¶, an evidence summary¶ and relevant OPTIKNEE systematic review(s).

At the start of each meeting attendees were reminded of the consensus goals, context (secondary prevention of PTOA) and guiding principles (inclusive respectful conversations, solution focused comments).

Each meeting included a presentations of definitions or recommendations and supporting evidence; small group breakout room discussions (~6/group); small group discussion summaries to the full group; full group discussion and summary.

Discussions were focused on the meaning and/or dissenting views of the definitions or recommendations.

Meetings were recorded, and facilitated by an expert external moderator (CLA).4 5 Small group discussions were led by expert group members, supported by a trainee (shared common definitions or recommendations slides and recorded breakout room interaction). Each small group prioritised specific definitions or recommendations to ensure all were discussed equally, but also discussed other items as time permitted.

After small groups shared their feedback, the full group elaborated on, or raised new discussion points. Experts could contribute to the discussion by using the raise hand or chat function, and key points were compiled using a real-time collaborative platform.††

After meetings, review leads and the steering committee incorporated the feedback and finalised the definitions and recommendations for voting.**

Rate recommendations (February–June 2022)

Within 2-3 weeks of each meeting, the steering committee and expert group were sent an anonymous link to an online survey‡‡ to rate the level of appropriateness and record comments/dissenting viewpoints, for the definitions or recommendations discussed.

Level of appropriateness was based on a 9-point Likert scale (1 = not appropriate and 9 = most appropriate).6 Scores were pooled and items with a median score of 1–3 were considered inappropriate, 4–6 uncertain and 7–9 appropriate as per the RAM.6 Variability of voting was categorised as small (≤3 points), moderate (4–5 points) and large (≥6 points).

*Open Science Framework Sharing Page.

†https://osf.io/7tfxn/.

‡With the exception of the Burden systematic review which did not restrict based on age of injury.

§Zoom.

¶Seee online supplemental file 1.

**See online supplemental file 3.

††Padlet.

‡‡REDCap.

ACL, anterior cruciate ligament; GRADE, Grading of Recommendations Assessment, Development and Evaluation;, OA, osteoarthritis; PRISMA, Preferred Reporting Items for Systematic reviews and Meta-Analyses; PROs, patient-reported outcomes; PTOA, post-traumatic osteoarthritis; RAM, RAND UCLA Appropriateness Method.

Table 1

Overview of systematic reviews

Figure 1

OPTIKNEE seven-step consensus approach.

Patient and public involvement

One individual with lived experience of ACL tear (and ACL reconstruction (ACLR)) and four clinicians (ie, physiotherapists and orthopaedic surgeons) contributed to the priority theme setting for the OPTIKNEE consensus. One patient partner and one clinician (sports and exercise medicine physician) were authors on the risk factor review,29 and one additional patient and clinician partner provided feedback on one of the intervention reviews.30 A patient partner and a clinician (physiotherapist) provided feedback on this manuscript.

Mitigation

Consensus exercises can be vulnerable to persuasion (bias) by the steering group31 and dominant personalities,32 lack generalisability and inadvertently suppress contrary opinions that may be vital for moving the field forward.33 Several steps were taken to mitigate these potential downfalls. Steering committee members did not participate in the small group conversations and only contributed to the full group discussions during the consensus meetings when invited, there was a need for clarification, or when they sought guidance from the larger group. We engaged an experienced external moderator (CLA) and used small group discussions, to mitigate the influence of dominant personalities and support all expert group members to contribute. Finally, the unique perspectives of the expert group members contributed to exploring each definition and recommendation through varied lenses.

Role of funding source

The initial priority setting exercise was funded by a Canadian Institutes of Health Research Planning and Dissemination grant (principal investigator JLW #161821). No financial support was received for the systematic reviews or consensus.

Dissemination plan

After the consensus voting was complete, we engaged a ‘knowledge broker’ (a person who promotes interaction between researchers and end users)34 to develop and execute a dissemination plan to increase awareness and catalyse adoption of the recommendations among patients, healthcare providers, researchers and other stakeholders (eg, sports organisations and clubs, athletic associations, funding agencies, scholarly societies and healthcare funders).

ResultsExpert group demographics

The expert group (n=36) of 33 clinician scientists (29 physiotherapists, 2 sport and exercise medicine physicians, 1 orthopaedic surgeon and 1 chiropractor), and 3 scientists (sports science and kinesiology) included 21 women, 15 men and 1 of undisclosed gender with a mean (SD) age of 41 (12) years. Thirty three either currently or previously had, a patient caseload, and 15 had lived experience of a traumatic knee injury. The group spanned career stages (10 professor or professor emeritus, 3 associate professor, 6 assistant professor, research fellow, instructor, or research associates and 17 trainees, including 1 Master, 8 PhD and 7 post-doctoral fellows) and 9 countries (10 Australia, 8 Canada, 5 Denmark, 5 Norway, 2 Netherlands, 3 USA, 2 Sweden, 1 Ireland and 1 Italy), and was predominantly white (92% white, 5% southeast Asian, 2% west Asian and 1% other). All experts were fluent in English. Individual involvement at each stage is outlined in the online supplemental file 2.

Evidence synthesis

The seven systematic reviews we conducted to synthesise the evidence (table 1), incorporated the findings of approximately 230 studies containing data from >133 000 persons with traumatic knee injuries.17 29 30 35–38 Of the seven systematic reviews, four performed quantitative syntheses, and all seven performed semi-quantitative or narrative syntheses.

Definitions

Twenty-six definitions were developed to facilitate discussions. Eight definitions (ie, rehabilitation, prevention, structural and symptomatic knee OA, knee injury, knee PTOA and early-onset knee PTOA) represented core consensus concepts and were discussed at the first consensus meeting. The remaining 17 definitions were provided to the expert group for reference (see online supplemental file 3). One draft core definition (pre-PTOA) was removed after discussion, because it replicated the concept of ‘at-risk’. The remaining 7 core definitions were deemed appropriate with agreement ranging from 7 to 9 (table 2). Voting distribution and dissenting viewpoints are summarised in the online supplemental file 3.

Table 2

Core definitions and voting results

Recommendations

Figures 2–4 contain the 8 clinical (with 30 subcomponents) and 6 research (with 19 sub-components) recommendations, and a summary of their appropriateness based on expert group voting. A detailed summary of the supporting evidence, voting results and all dissenting viewpoints for all recommendations can be found in online supplemental file 3. The recommendations apply to any traumatic knee injury and/or associated surgery unless otherwise indicated. Symptomatic PTOA was prioritised over structural PTOA, given that pain, disability and impaired quality of life drive the burden of OA and the variable relationship between structure and symptoms. High level themes that unite the recommendations include an expanded focus beyond ACL tears, the complementary nature of exercise-based and surgical interventions, a lifespan approach to mitigating knee PTOA risk and person-centred approach.

Figure 2

Clinical recommendations 1–4 and appropriateness rating. *See online supplemental file 3) for level of supporting evidence, results of expert group appropriateness voting and dissenting viewpoints for all recommendations (and components). ∧See online supplemental file 4, for example. †Applicable to patients who have had an ACL tear and/or undergone an ACLR but may not apply to every individual and situation. The patient and healthcare provider should consider the unique features of a patient’s injury, the resources available to them and their unique situation when developing a treatment plan. ‡Choice of domain(s) will vary based on individual presentation, goals and practicality. Appropriateness rating: ✓ = recommendation is appropriate (median scores: ≥7/9), ? = recommendation is uncertain (median scores: 4–6), X = recommendation is not appropriate (median scores: 1–3). ACL, anterior cruciate ligament; ACLR, ACL reconstruction; OA, osteoarthritis; PTOA, post-traumatic osteoarthritis; QOL, quality of life.

Figure 3

Clinical recommendations 5–8 and appropriateness rating. *See online supplemental file 3 for level of supporting evidence, results of expert group appropriateness voting and dissenting viewpoints for all recommendations (and components). ∧See supplementary file for examples. appropriateness rating: ✓ = recommendation is appropriate (median scores: ≥7/9), ? = recommendation is uncertain (median scores: 4–6) and X = recommendation is not appropriate (median scores 1–3). aInstrument choice will vary by individual presentation, goals, practicality, and instrument availability. domains and instruments are presented alphabetically. Licencing requirements may apply but might be available through an employer. bThe capacity of a muscle to do work (eg, strength, power and endurance). cStrength tests should only be performed when safe. Isometric scores are not interchangeable with isokinetic or isotonic scores. As hand-held dynamometry can underestimate strength, it is important to secure the femur, have the patient push into resistance generated by a fixed belt and for re-assessment to be conducted by the same assessor. 1RM should be based on the average of at least two measures of maximum effort. dThe action of carrying out or accomplishing a movement, movement task or movement activity. eHop tests should only be performed when safe. Test choice may be influenced by individual presentation, goals, practicality, and availability of space. Test is presented in alphabetical order as there is insufficient evidence to inform the ‘best’ test or ‘best’ order. ACL, anterior cruciate ligament; ACL-QOL, ACL quality-of-life score; ACLR, ACL reconstruction; ACL-RSI, ACL Return to Sport after Injury Scale; IKDC-SKF, International Knee Documentation Committee Subjective Knee Form; K-SES, Knee Self-Efficacy Scale; KOOS. Knee Injury and Osteoarthritis Outcome Score; PTOA, post-traumatic osteoarthritis; QOL, quality of life; RM, repetition maximum; TSK, Tampa Scale of Kinesiophobia; WOMET, Western Ontario Meniscal Evaluation Tool.

Figure 4

Research recommendations and appropriateness rating. *See online supplemental file 3 for level of supporting evidence, results of expert group appropriateness voting and dissenting viewpoints for all recommendations (and components). ∧See supplementary file for examples. Level of appropriateness of the recommendation: appropriateness rating: ✓ = recommendation is appropriate (median scores: ≥7/9), ? = recommendation is uncertain (median scores: 4–6) and X = recommendation is not appropriate (median scores: 1–3). aExamples: NICE,61 American College of Rheumatology,62 European League against Rheumatism63 definitions. bDomains and instruments are presented in no particular order. Licencing requirements may apply. cProvides an overall composite score of knee-related symptoms, function and sports activities. dProvides single domain scores for knee-related pain, other symptoms, function in daily living, function in sport and recreation and quality of life, as well as a composite (KOOS4) score of knee-related pain, other symptoms, function in sport and recreation, quality of life. eProvides an overall composite score of knee-related physical symptoms, sports/recreation/work/lifestyle, and emotions. fThe capacity of a muscle to do work (eg, strength, power, endurance). gStrength tests should only be performed when safe. Isometric scores are not interchangeable with isokinetic or isotonic scores. As HHD can underestimate strength, it is important to secure the femur, have the patient push into resistance generated by a fixed belt, and for re-assessment to be conducted by the same assessor. 1RM should be based on the average of at least two measures of maximum effort. hThe action of carrying out or accomplishing a movement, movement task or movement activity. iHop tests should only be performed when safe. Test choice may be influenced by individual presentation, goals, practicality and availability of space. Test is presented in alphabetical order as there is insufficient evidence to inform the ‘best’ test or ‘best’ order. ACL anterior cruciate ligament; ACL-QOL, ACL Quality-of-Life Score; ACLR, ACL reconstruction; ACL-RSI, ACL Return to Sport after Injury Scale; BMI, body mass index; EQ-5D, EuroQol 5 Dimensions; GROC, Global Rate of Change; HHD, hand-held dynamometry; IKDC-SKF, International Knee Documentation Committee Subjective Knee Form; KOOS, Knee injury and Osteoarthritis Outcome Score pain, other symptoms, function in sport and recreation (SportRec) and knee-related QOL subscales; K-SES, Knee Self-Efficacy Scale; NICE, National Institute for Health and Care Excellence; NRS, Numerical Rating Scale; pass, Patient acceptable symptom state; PTOA, post-traumatic osteoarthritis; PROs, patient-reported outcomes ; QOL, quality of life; RCT, randomised controlled trial; RM, repetition maximum; SF-12, short form 12; SF-36, short form 36; TSK, Tampa Scale of Kinesiophobia; VAS, Visual Analogue Scale; WOMET, Western Ontario Meniscal Evaluation Tool.

Clinical recommendations: the 8 clinical recommendations address who to target, when and how to target and what outcomes to monitor to manage traumatic knee injuries and mitigate the burden of symptomatic knee PTOA. The certainty of evidence for the clinical recommendations ranged from expert opinion to a GRADE (Grading of Recommendations Assessment, Development and Evaluation)39 rating of moderate (burden, risk factors and interventions) or high (patient-reported outcomes (PROs), strength tests and functional performance tests). GRADE is a method for rating the certainty of evidence and strength of a recommendation.40 All eight recommendations were rated as appropriate except for two subcomponents related to adjunct treatments (blood-flow restriction training and whole-body vibration) to improve quadriceps strength after an ACL tear or ACLR, which were rated as uncertain (figures 2 and 3). The median (minimum–maximum) agreement across the clinical recommendations was 9 (4.5–9).

Research recommendations: the 6 research recommendations address priorities for knee injury and PTOA research, study design considerations and what outcomes to monitor. One additional draft recommendation (how to interpret outcome changes) was removed after the consensus meeting, because there was insufficient evidence available to inform a recommendation.36–38 Instead, guidance on interpreting changes in recommended PROs, muscle function and functional performance tests is provided in online supplemental file 4, and recommendation on thresholds for minimal important change, patient acceptable symptom state and treatment failure are summarised in the PROs systematic review.36 The certainty of evidence for the research recommendations ranged from expert opinion to a GRADE39 rating of moderate (burden, risk factors and interventions) or high (PROs, strength tests and functional performance tests). All 6 recommendations and subcomponents voted on were deemed appropriate (figure 4), with the median (minimum–maximum) agreement across recommendations of 9 (7–9). Voting distribution and dissenting viewpoints are summarised in the online supplemental file 3.

Discussion

The OPTIKNEE consensus meetings produced 8 clinical and 6 research recommendations. We encourage clinicians to integrate the clinical recommendations alongside their own expertise, individual patient preferences and available resources (eg, time and equipment) to provide best-practice care (Box 2). Clinician scientists and researchers can leverage the research recommendations and dissenting viewpoints to conduct rigorous and transparent research to propel the field of knee injury rehabilitation and PTOA prevention forward. These recommendations can also empower patients to advocate for person-centred evidence-based treatments, and to increase awareness about preventing the long-term consequences of traumatic knee injuries among other stakeholder groups.

Box 2 How to apply the OPTIKNEE clinical recommendationsWhich patients to discuss and address the risk of knee PTOA with?

All people with single and multi-structure knee injuries have an elevated risk for PTOA and should be aware of it.

Those with high risk (ie, intra-articular damage) or symptoms (eg, pain) and/or functional restrictions (eg, less physically active) persisting beyond usual recovery times, or with subsequent knee injury should be taught how to manage this risk.

What can be done to help reduce a patient’s risk of knee PTOA and when to do it?

Collaborate with the patient to meet their informational needs for knee health and OA (education), guide them to self-manage and teach them how to avoid or address risk factors for non-traumatic OA (eg, weight gain, inactivity and thigh muscle weakness) through person-centred goals.

Start these efforts as close to the time of their knee injury as possible and continue across the lifespan.

What is evidence-based care for ACL tears?

In most cases, treatment of an ACL tear should start with education and exercise-based rehabilitation (not surgery).

Ask the patient who they want to work with to make decisions about their knee health and who needs to be ‘in the room’ for decisions.

Start a dialogue with the patient (and other stakeholders) about their goals, fears or anxieties, preferences, available resources and go-no-go criteria for non-surgical care, ACLR, supervised rehabilitation, return to activity (training, sport and occupation as appropriate) and ongoing self-management.

The patient should guide the choice and setting for exercise therapy, but it should include weight-bearing, mobility and open and closed kinetic chain resistance-based neuromuscular control and plyometric exercises that target the leg muscles (specifically, the quadriceps and hamstring) with a dose sufficient to stimulate physiological adaptation.

To promote the patient’s engagement in their exercise program, co-develop short, intermediate and long-term SMART (specific, measurable, attainable, relevant and timebound) goals.

Guide patients through progressively challenging movement patterns (that are relevant to their lifestyle) to detect motions associated with anxiety or fear, and then encourage them to mindfully explore and expose themselves to that motion or its subcomponents.

What are the most important outcomes to monitor after traumatic knee injury and best options to do it?

Choose PROs, muscle strength tests and hop tests based on each patient’s presentation and goals, and the available resources.

PROs that assess multiple outcome domains and provide a composite score across various knee injury types may be most practical.

Some PROs are freely available while other have licencing requirements but could be available through your employer.

How and when should monitoring important outcomes be done after a traumatic knee injury?

Consider assessing at least 1 multidomain PRO, 1 knee extensor and flexor strength test, and 1 hop test at a patients’ first and last treatment session, and every 4–6 weeks in between (as applicable).

Consider asking patients to complete PROs in the waiting room before their treatment session.

What is the best way to interpret and record the current state and change of important outcomes?

Ask the patient if they feel their current state is acceptable/satisfactory and if they have noticed a meaningful change in the outcome.

Consider asking the patient about responses to individual PROs items to understand their experience.

Record the baseline and follow-up score, change in direction (improvement or deterioration) in the outcome, if the patient felt the change was meaningful and if they feel that their current state of that outcome is acceptable/satisfactory§.

*Outcomes and measures are presented in no particular order.

†Freely available at www.koos.nu.

‡For use after meniscal injuries only.

§See online supplemental file 4 for further examples.

¶For use after ACL tear injuries only.

**The capacity of a muscle to do work (eg, strength, power and endurance).

††Strength tests should only be performed when it is safe. Isometric scores are not interchangeable with isokinetic or isotonic scores. As HHD can underestimate strength, it is important to secure the femur, have the patient push into resistance generated by a fixed belt (not the assessor hand) and for re-assessment to be conducted by the same assessor. 1RM should be based on the average of at least two repeated measures of maximum effort.

‡‡The action of carrying out or accomplishing a movement, movement task or movement activity.

§§Hop tests should only be performed when it is safe.

6 m THT, 6-metre Timed Hop Test; ACL, anterior cruciate ligament, ACL-QOL, ACL Quality-of-Life Score; ACLR,ACL reconstruction; ACL-RSI, ACL Return to Sport after Injury Scale; CHT, Crossover Hop Test; HHD, Hand-held dynamometry; IKDC-SKF, International Knee Documentation Committee Subjective Knee Form; K-SES, Knee Self-Efficacy Scale; KOOS, Knee injury and Osteoarthritis Outcome Score; NRS, Numerical Rating Scale; PTOA, post-traumatic osteoarthritis; PROs, patient-reported outcomes ; QOL, quality of life; RM, repetition maximum; SHT, Single Hop Test; THT, Triple Hop Test; TSK, Tampa Scale of Kinesiophobia; VAS, Visual Analogue Scale; VHT, Vertical Hop Test; WOMET, Western Ontario Meniscal Evaluation Tool.

Clinical implications and call to action

Decades of research have established that traumatic knee injuries increase the risk of OA. Despite this, widespread clinical actions to promote knee health have not been implemented. There are many barriers to preventative healthcare for knee PTOA. Frontline healthcare providers tend to focus on acute knee injury recovery and return to activity/work/sport, and rarely prioritise their role in preventing knee PTOA or other long-term consequences. To complicate matters, people who experience knee injuries rarely understand their risk for OA, nor seek or receive care beyond the precipitating knee injury.20–22 More broadly, there is a lack of high level evidence and until now, consensus guidelines to guide treatment decisions. This has left clinicians guessing about whom to target, when and how to intervene and what outcomes to monitor.

The OPTIKNEE clinical recommendations are an important first step in overcoming barriers to prevent knee PTOA. The recommendations highlight the elevated risk for PTOA across people with a variety of traumatic knee injuries (including but beyond an ACL tear) and the need to promote knee and overall health in all patients. Considering the resource constraints of the clinical setting, the recommendations highlight PROs that assess multiple outcome domains (useful when time is limited) and single outcome domains (useful when deeper understanding is needed), and guidance on how to assess and interpret muscle function and functional performance when sophisticated equipment is, and is not, available. The recommendations highlight exercise-based interventions as core first-line treatments for knee injuries and PTOA prevention, and the importance of equipping patients with the knowledge and skills to self-manage their knee health over their lifespan. Finally, as exercise is a behaviour, the recommendations recognise several behaviour change techniques,41 including goal setting (goal-based criteria), feedback on exercise (early supervision and semi-supervision) and social support (a collaborative therapeutic alliance and person-centred approach) as important for promoting exercise engagement.42

The clinical recommendations may not be as prescriptive as some may desire, due to a paucity of evidence. For example, the recommendations do not include a menu of specific exercises or detailed exercise dosages to reduce the risk of knee symptoms and PTOA. Instead, general principles that point to the value of resistance-based, neuromuscular control and plyometric exercises can be used to develop personalised exercise-based programmes.43–45 Clinicians can feel confident about the safety of open and closed chain exercises that target the quadriceps and hamstrings, and neuromuscular electrical stimulation to promote quadriceps strength. In contrast, the expert group recommends caution for the routine use of both blood-flow restriction training, and whole-body vibration to improve quadriceps strength, and against use of continuous passive motion, and knee bracing.

We expect the OPTIKNEE clinical recommendations will spark debate. Surfacing dissenting viewpoints among the expert group (see online supplemental file 3) is a strength of quality consensus statements,33 46 and can promote shared decision-making with stakeholders (eg, patients). Expert group dissent centred around how to operationalise the decision that a patient has completed sufficient rehabilitation and should consider ACLR; the value of bracing early post-surgery to restrict motion (meniscal repair) or promote weight-bearing (ACLR) and to temper fear or anxiety of movement; and the feasibility of single domain PROs, hop test battery and formal muscle function (strength, endurance and power) testing in clinical settings.

Research implications and call to action

To move the field of PTOA prevention forward, unique challenges to study design and data synthesis need to be overcome. Some of the biggest hurdles are a lack of a standardised definition of early PTOA, the need for lengthy follow-up to assess for the development and/or progression of PTOA, and adequate participant retention and/or sample sizes to ensure sufficient participants to control for confounding factors (eg, injury type, injury management and physical activity). Data synthesis, which is a solution to the sample size barrier, is currently impeded by variability in outcomes measures, and the tests or instruments we use. Perhaps, most importantly, much of the research in the field of traumatic knee injuries and PTOA has focused on structural and molecular definitions of OA, when symptomatic OA drives the individual and societal burden. This disconnect leaves us with a limited understanding of the mechanisms underlying symptomatic PTOA.

The OPTIKNEE research recommendations are an important step to overcome the barriers that interfere with conducting PTOA prevention research and data synthesis. To enhance understanding of clinical trajectories following traumatic knee injury, the recommendations advocate to include patient groups beyond those with an ACL tear treated with ACLR, emphasise the importance of symptomatic definitions of PTOA, and need to follow patients for at least 5 years (if possible) from time of injury. To facilitate data synthesis, the recommendations include a core group of outcome domains, other important domains and current best methods to assess those domains based on their measurement properties, including interpretability.

Despite including information from ~230 individual studies in the OPTIKNEE systematic reviews, many of the clinical recommendations were based on very-low certainty of evidence or expert opinion (in the absence of empirical evidence). What is often missing is the information to translate evidence into the clinical setting or to act beyond knee injury to mitigate PTOA risk. For example, we have identified unmodifiable risk factors for knee PTOA, but not modifiable risk factors (ie, treatment targets)