The Bone & Joint Journal has published several consensus statements in recent years, many of which have positively influenced clinical practice and policy. 1-13. However, even the most valued consensus statements have limitations, and all ultimately represent Level V evidence. Consensus studies add greatest value where higher-order evidence to aid decision making is ambiguous or lacking. In all settings, care must be taken to critically appraise standards of methodology, with particular attention to potential biases that may influence the conclusions which are drawn. Cite this article: Bone Joint J 2023;105-B(4):343–346

Aims. The aim of this study was to establish consensus statements on the diagnosis, nonoperative management, and indications, if any, for medial patellofemoral complex (MPFC) repair in patients with patellar instability, using the modified Delphi approach. Methods. A total of 60 surgeons from 11 countries were invited to develop consensus statements based on their expertise in this area. They were assigned to one of seven working groups defined by subtopics of interest within patellar instability. Consensus was defined as achieving between 80% and 89% agreement, strong consensus was defined as between 90% and 99% agreement, and 100% agreement was considered to be unanimous. Results. Of 27 questions and statements on patellar instability, three achieved unanimous consensus, 14 achieved strong consensus, five achieved consensus, and five did not achieve consensus. Conclusion. The statements that reached unanimous consensus were that an assessment of physeal status is critical for paediatric patients with patellar instability. There was also unanimous consensus on early mobilization and resistance training following nonoperative management once there is no apprehension. The statements that did not achieve consensus were on the importance of immobilization of the knee, the use of orthobiologics in nonoperative management, the indications for MPFC repair, and whether a vastus medialis oblique advancement should be performed. Cite this article: Bone Joint J 2023;105-B(12):1259–1264

Aims. The aim of this study was to establish consensus statements on medial patellofemoral ligament (MPFL) reconstruction, anteromedialization tibial tubercle osteotomy, trochleoplasty, and rehabilitation and return to sporting activity in patients with patellar instability, using the modified Delphi process. Methods. This was the second part of a study dealing with these aspects of management in these patients. As in part I, a total of 60 surgeons from 11 countries contributed to the development of consensus statements based on their expertise in this area. They were assigned to one of seven working groups defined by subtopics of interest. Consensus was defined as achieving between 80% and 89% agreement, strong consensus was defined as between 90% and 99% agreement, and 100% agreement was considered unanimous. Results. Of 41 questions and statements on patellar instability, none achieved unanimous consensus, 19 achieved strong consensus, 15 achieved consensus, and seven did not achieve consensus. Conclusion. Most statements reached some degree of consensus, without any achieving unanimous consensus. There was no consensus on the use of anchors in MPFL reconstruction, and the order of fixation of the graft (patella first versus femur first). There was also no consensus on the indications for trochleoplasty or its effect on the viability of the cartilage after elevation of the osteochondral flap. There was also no consensus on postoperative immobilization or weightbearing, or whether paediatric patients should avoid an early return to sport. Cite this article: Bone Joint J 2023;105-B(12):1265–1270

The February 2024 Knee Roundup. 360. looks at: Do patients with hypoallergenic total knee arthroplasty implants for metal allergy do worse? An analysis of healthcare utilizations and patient-reported outcome measures; Defining a successful total knee arthroplasty; Incidence, microbiological studies, and factors associated with periprosthetic joint infection after total knee arthroplasty; A modified Delphi consensus statement on patellar instability; Cause for concern? Significant cement coverage in retrieved metaphyseal cones after revision total knee arthroplasty; Prevalence of post-traumatic osteoarthritis after anterior cruciate ligament injury remains high despite advances in surgical techniques; Cost-effectiveness of arthroscopic partial meniscectomy versus physical therapy for traumatic meniscal tears in patients aged under 45 years

Aims. The aim of this study was to gain a consensus for best practice of the assessment and management of children with idiopathic toe walking (ITW) in order to provide a benchmark for practitioners and guide the best consistent care. Methods. An established Delphi approach with predetermined steps and degree of agreement based on a standardized protocol was used to determine consensus. The steering group members and Delphi survey participants included members from the British Society of Children’s Orthopaedic Surgery (BSCOS) and the Association of Paediatric Chartered Physiotherapists (APCP). The statements included definition, assessment, treatment indications, nonoperative and operative interventions, and outcomes. Descriptive statistics were used for analysis of the Delphi survey results. The AGREE checklist was followed for reporting the results. Results. A total of 227 participants (54% APCP and 46% BSCOS members) completed the first round, and 222 participants (98%) completed the second round. Out of 54 proposed statements included in the first round Delphi, 17 reached ‘consensus in’, no statements reached ‘consensus out’, and 37 reached ‘no consensus’. These 37 statements were then discussed, reworded, amalgamated, or deleted before the second round Delphi of 29 statements. A total of 12 statements reached ‘consensus in’, four ‘consensus out’, and 13 ‘no consensus’. In the final consensus meeting, 13 statements were voted upon. Five were accepted, resulting in a total of 31 approved statements. Conclusion. In the aspects of practice where sufficient evidence is not available, a consensus statement can provide a strong body of opinion that acts as a benchmark for excellence in clinical care. This statement can assist clinicians managing children with ITW to ensure consistent and reliable practice, and reduce geographical variability in practice and outcomes. It will enable those treating ITW to share the published consensus document with both carers and patient groups. Cite this article: Bone Joint J 2024;106-B(10):1190–1196

Aims. The aim of this study was to determine the consensus best practice approach for the investigation and management of children (aged 0 to 15 years) in the UK with musculoskeletal infection (including septic arthritis, osteomyelitis, pyomyositis, tenosynovitis, fasciitis, and discitis). This consensus can then be used to ensure consistent, safe care for children in UK hospitals and those elsewhere with similar healthcare systems. Methods. A Delphi approach was used to determine consensus in three core aspects of care: 1) assessment, investigation, and diagnosis; 2) treatment; and 3) service, pathways, and networks. A steering group of paediatric orthopaedic surgeons created statements which were then evaluated through a two-round Delphi survey sent to all members of the British Society for Children’s Orthopaedic Surgery (BSCOS). Statements were only included (‘consensus in’) in the final agreed consensus if at least 75% of respondents scored the statement as critical for inclusion. Statements were discarded (‘consensus out’) if at least 75% of respondents scored them as not important for inclusion. Reporting these results followed the Appraisal Guidelines for Research and Evaluation. Results. A total of 133 children’s orthopaedic surgeons completed the first survey, and 109 the second. Out of 43 proposed statements included in the initial Delphi, 32 reached ‘consensus in’, 0 ‘consensus out’, and 11 ‘no consensus’. These 11 statements were then reworded, amalgamated, or deleted before the second Delphi round of eight statements. All eight were accepted as ‘consensus in’, resulting in a total of 40 approved statements. Conclusion. In the many aspects of medicine where relevant evidence is not available for clinicians to base their practice, a Delphi consensus can provide a strong body of opinion that acts as a benchmark for good quality clinical care. We would recommend clinicians managing children with musculoskeletal infection follow the guidance in the consensus statements in this article, to ensure care in all medical settings is consistent and safe. Cite this article: Bone Joint J 2023;105-B(7):815–820

Chondrosarcoma is the second most common surgically treated primary bone sarcoma. Despite a large number of scientific papers in the literature, there is still significant controversy about diagnostics, treatment of the primary tumour, subtypes, and complications. Therefore, consensus on its day-to-day treatment decisions is needed. In January 2024, the Birmingham Orthopaedic Oncology Meeting (BOOM) attempted to gain global consensus from 300 delegates from over 50 countries. The meeting focused on these critical areas and aimed to generate consensus statements based on evidence amalgamation and expert opinion from diverse geographical regions. In parallel, periprosthetic joint infection (PJI) in oncological reconstructions poses unique challenges due to factors such as adjuvant treatments, large exposures, and the complexity of surgery. The meeting debated two-stage revisions, antibiotic prophylaxis, managing acute PJI in patients undergoing chemotherapy, and defining the best strategies for wound management and allograft reconstruction. The objectives of the meeting extended beyond resolving immediate controversies. It sought to foster global collaboration among specialists attending the meeting, and to encourage future research projects to address unsolved dilemmas. By highlighting areas of disagreement and promoting collaborative research endeavours, this initiative aims to enhance treatment standards and potentially improve outcomes for patients globally. This paper sets out some of the controversies and questions that were debated in the meeting. Cite this article: Bone Joint J 2024;106-B(5):425–429

Aims. A national screening programme has existed in the UK for the diagnosis of developmental dysplasia of the hip (DDH) since 1969. However, every aspect of screening and treatment remains controversial. Screening programmes throughout the world vary enormously, and in the UK there is significant variation in screening practice and treatment pathways. We report the results of an attempt by the British Society for Children’s Orthopaedic Surgery (BSCOS) to identify a nationwide consensus for the management of DDH in order to unify treatment and suggest an approach for screening. Methods. A Delphi consensus study was performed among the membership of BSCOS. Statements were generated by a steering group regarding aspects of the management of DDH in children aged under three months, namely screening and surveillance (15 questions), the technique of ultrasound scanning (eight questions), the initiation of treatment (19 questions), care during treatment with a splint (ten questions), and on quality, governance, and research (eight questions). A two-round Delphi process was used and a consensus document was produced at the final meeting of the steering group. Results. A total of 60 statements were graded by 128 clinicians in the first round and 132 in the second round. Consensus was reached on 30 out of 60 statements in the first round and an additional 12 in the seond. This was summarized in a consensus statement and distilled into a flowchart to guide clinical practice. Conclusion. We identified agreement in an area of medicine that has a long history of controversy and varied practice. None of the areas of consensus are based on high-quality evidence. This document is thus a framework to guide clinical practice and on which high-quality clinical trials can be developed. Cite this article: Bone Joint J 2023;105-B(2):209–214

Aims. The Ponseti method is the gold standard treatment for congenital talipes equinovarus (CTEV), with the British Consensus Statement providing a benchmark for standard of care. Meeting these standards and providing expert care while maintaining geographical accessibility can pose a service delivery challenge. A novel ‘Hub and Spoke’ Shared Care model was initiated to deliver Ponseti treatment for CTEV, while addressing standard of care and resource allocation. The aim of this study was to assess feasibility and outcomes of the corrective phase of Ponseti service delivery using this model. Methods. Patients with idiopathic CTEV were seen in their local hospitals (‘Spokes’) for initial diagnosis and casting, followed by referral to the tertiary hospital (‘Hub’) for tenotomy. Non-idiopathic CTEV was managed solely by the Hub. Primary and secondary outcomes were achieving primary correction, and complication rates resulting in early transfer to the Hub, respectively. Consecutive data were prospectively collected and compared between patients allocated to Hub or Spokes. Mann-Whitney U test, Wilcoxon signed-rank test, or chi-squared tests were used for analysis (alpha-priori = 0.05, two-tailed significance). Results. Between 1 March 2020 and 31 March 2023, 92 patients (139 feet) were treated at the service (Hub 50%, n = 46; Spokes 50%, n = 46), of whom nine were non-idiopathic. All patients (n = 92), regardless of allocation, ultimately achieved primary correction, with idiopathic patients at the Hub requiring fewer casts than the Spokes (mean 4.0 (SD 1.4) vs 6.9 (SD 4.4); p < 0.001). Overall, 60.9% of Spokes’ patients (n = 28/46) required transfer to the Hub due to complications (cast slips Hub n = 2; Spokes n = 17; p < 0.001). These patients ultimately achieved full correction at the Hub. Conclusion. The Shared Care model was found to be feasible in terms of providing primary correction to all patients, with results comparable to other published services. Complication rates were higher at the Spokes, although these were correctable. Future research is needed to assess long-term outcomes, parents’ satisfaction, and cost-effectiveness. Cite this article: Bone Jt Open 2023;4(11):865–872

Abstract. High tibial osteotomy (HTO) is a well-recognised procedure to address medial compartment osteoarthritis (OA). There remains dispute on the impact of pre-operative patient factors on patient related outcome measures (PROMS). Does BMI and age affect > 2 year and > 5 year oxford knee scores (OKS) and Knee injury and osteoarthritis outcome scores (KOOS). A retrospective review of a prospectively collected database was performed. Timeframe was 26/6/2014 and 25/8/2022. BMI and age were recorded. OKS and KOOS were collected at > 2 years and > 5 years. There were 81 procedures included, of these 50 had OKS and KOOS scores at > 2 years and 35 at > 5 years. Median BMI was 28.5kg/m. 2. , range was 18.6–40.8kg/m. 2. Spearman's rank for >2 year OKS was p(df)=−0.210 p=0.157, > 5 year OKS p(df)=−0.215 p=0.230. For > 2 year and > 5 year KOOS subscales there were no statistically significant associations on Spearman's rank. For age, median age was 52.5, range 26–71 years old. OKS at >2 year p(df)=0.068 p=0.664, OKS >5 years p(df)=0.065 p= 0.709. For >2 year and > 5 year KOOS subscales there were no statistically significant associations on Spearman's rank. There were no adverse outcome in patients up-to the age of 71. There were no statistically significant Spearman's rank correlations between PROMS and OKS/KOOS scores. This supports recent KOG consensus statement highlighting physiological age importance vs chronological age. Of note there were more negative associations in the BMI group compared with age

Background. Advice and education are considered vital components of back pain care within national guidelines. However, a recent systematic review only found low grade evidence for a small average effect. They also reported wide heterogeneity in intervention design and delivery. This review aimed to understand why intervention design varied and what limited effectiveness by examining the underlying theoretical foundations of the studies from that review. Method. Population, context, selection criteria, intervention(s), control, outcome measures, how the intervention was hypothesised to produce outcomes and author recommendations based on results of the study were extracted from text records. The extent to which the advice included matched a published international consensus statement on evidence-based advice for back pain was recorded. Whether interventions or settings were complex was determined using the Medical Research Council complex intervention development and evaluation guidance and the extent to which they met complexity reporting criteria was recorded. Results. The review included 26 trials conducted over 25 years. Differences In causal pathways could explain diversity in intervention design but these were not clearly described or evaluated. All studies were complex in terms of intervention and setting. This was rarely considered in intervention and trial design or when discussing the results. Although interventions were frequently described in detail only a few explained the process and justification of the design. Theories of education or behaviour change were rarely applied. Conclusion. These studies have not deepened our understanding of how education improves outcomes. Future RCTs should engage more with theory and other theory-based research methods should to be considered. Conflict of interest: No conflicts of interest. Sources of funding: No funding

Aims. The aim of this study was to prepare a scoping review to investigate the use of biologic therapies in the treatment of musculoskeletal injuries in professional and Olympic athletes. Methods. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews and Arksey and O’Malley frameworks were followed. A three-step search strategy identified relevant published primary and secondary studies, as well as grey literature. The identified studies were screened with criteria for inclusion comprising clinical studies evaluating the use of biologic therapies in professional and Olympic athletes, systematic reviews, consensus statements, and conference proceedings. Data were extracted using a standardized tool to form a descriptive analysis and a thematic summary. Results. A total of 202 studies were initially identified, and 35 met criteria for the scoping review; 33 (94.3%) were published within the last eight years, and 18 (51.4%) originated from the USA. Platelet rich plasma was the most studied biologic therapy, being evaluated in 33 (94.3%) studies. Ulnar collateral ligament and hamstring injuries were the conditions most studied (nine (25.7%) studies and seven (20.0%) studies, respectively). Athletes most frequently participated in baseball, soccer, and American football. Only two (5.7%) studies were level 1 evidence, with interpretation and comparison between studies limited by the variations in the injury profile, biologic preparations, and rehabilitation protocols. Conclusion. There is diverse use of biologic therapies in the management of musculoskeletal injuries in professional and Olympic athletes. There is currently insufficient high-level evidence to support the widespread use of biologic therapies in athletes. Further research priorities include the development of condition/pathology-specific preparations of biologic therapies, and of outcome measures and imaging modalities sufficiently sensitive to detect differences in outcomes, should they exist. Cite this article: Bone Joint J 2021;103-B(7):1189–1196

Aims. The aim of this study was to gain an agreement on the management of idiopathic congenital talipes equinovarus (CTEV) up to walking age in order to provide a benchmark for practitioners and guide consistent, high-quality care for children with CTEV. Methods. The consensus process followed an established Delphi approach with a predetermined degree of agreement. The process included the following steps: establishing a steering group; steering group meetings, generating statements, and checking them against the literature; a two-round Delphi survey; and final consensus meeting. The steering group members and Delphi survey participants were all British Society of Children’s Orthopaedic Surgery (BSCOS) members. Descriptive statistics were used for analysis of the Delphi survey results. The Appraisal of Guidelines for Research & Evaluation checklist was followed for reporting of the results. Results. The BSCOS-selected steering group, the steering group meetings, the Delphi survey, and the final consensus meeting all followed the pre-agreed protocol. A total of 153/243 members voted in round 1 Delphi (63%) and 132 voted in round 2 (86%). Out of 61 statements presented to round 1 Delphi, 43 reached ‘consensus in’, no statements reached ‘consensus out’, and 18 reached ‘no consensus’. Four statements were deleted and one new statement added following suggestions from round 1. Out of 15 statements presented to round 2, 12 reached ‘consensus in’, no statements reached ‘consensus out’, and three reached ‘no consensus’ and were discussed and included following the final consensus meeting. Two statements were combined for simplicity. The final consensus document includes 57 statements allocated into six successive stages. Conclusion. We have produced a consensus document for the treatment of idiopathic CTEV up to walking age. This will provide a benchmark for standard of care in the UK and will help to reduce geographical variability in treatment and outcomes. Appropriate dissemination and implementation will be key to its success. Cite this article: Bone Joint J 2022;104-B(6):758–764

Purpose. To establish if the subjective features of both bilateral leg pain and sexual dysfunction are presenting features in cauda equina syndrome (CES). Background. There appears to be conflicting expert opinion ‘red flag’ symptoms in the context of CES with many experts basing clinical decisions on the objective clinical findings only. Bilateral radiculopathy has been suggested as a possible sign of suspected CES, although a consensus statement by BASS and SBNS makes no reference to either this or sexual dysfunction. However, bilateral leg pain is included in the NICE clinical knowledge summary and sexual dysfunction is highlighted within CES guidance by the American Association of Neurological Surgeons. Methods. The clinical documentation of patients undergoing urgent magnetic resonance imaging (MR) due to clinical suspicion of cauda equina syndrome (CES) was reviewed over 12 months. Patients questioned regarding sexual function were included in this retrospective analysis (n=179), along with those with bilateral leg pain (n=294). Patients with confirmed cauda equina compression (CES +ve) were compared to those without (CES -ve). A logistic regression was applied to find the odds ratio. Results. In CES +ve 37.5% had sexual dysfunction, 48% had bilateral leg pain. CES –ve 14% had sexual dysfunction, 27% bilateral leg pain. Both significant to p=0.015 with an odds ratio of 3.6 and 2.5 respectively. Conclusions. Both sexual dysfunction and bilateral leg pain do appear to be ‘red flags’ for CES and should therefore be asked in the ED to aid clinical reasoning when suspecting this diagnosis. No conflicts of interest. No funding obtained

Mechanical methods of deep vein thrombosis (DVT) prophylaxis rely on the prevention of venous stasis – one of Virchow’s triad of cause of DVT. Mechanical methods, such as the A-V Impulse System (Orthofix Vascular Novamedix, Andover, UK) are used widely in orthopaedic surgery for the prevention of DVT, especially after elective orthopaedics. The evidence for the use of the A-V Impulse System in elective orthopaedics is widely accepted and is considered a Grade A Recommendation by the International Consensus Statement. These data are reviewed and critiqued. More recent studies show how mechanical methods can offer benefits to the patient outside of hip and knee replacement surgery. Data are presented on how such devices can effectively reduce swelling, DVT, compartment pressure and pain associated with trauma, based on over 20 years of practical experience. The practical implications of using these devices is discussed

There is currently wide variation in the management of patients who are anticoagulated with Warfarin and require urgent orthopaedic surgery. These form an important and significant group of patients, in terms of real numbers (at least 5,600 per annum in the UK). A study was initiated with an audit of 34 patients presenting to the West Wales unit who were warfarinised at admission and required trauma surgery. Observations were recorded about their pre-operative management and the delay this caused in taking the patient to theatre. 6 months later, a similar group of patients were re-audited. The mean delay to surgery in those patients in whom the INR was left to fall spontaneously was 5.5 days. Following administration of 1mg i.v. Vitamin K in those patients without cardiac valves, re-audit showed the mean delay reduced to 2.2 days. Representations from at least 6 major specialties were considered and a consensus statement was derived. Standardised protocols, which hinge on whether or not the patient has or does not have a cardiac valve were devised. Vitamin K should not be given to those patients with a cardiac valve and early consultation with cardiology and anaesthetics is recommended, with consideration of referral to a specialist cardiothoracic unit. For those patients without a cardiac valve, 1mg of Vitamin K may be administered, repeated as necessary until the INR is less than 1.8. Intravenous Heparin should be provided in the interim whilst the patient is waiting for surgery. This is discontinued the morning of surgery and subcutaneous Heparin reinstated post-operatively. These recommendations have been trialled in the two units involved in the study and have been relatively safe and easy to implement

Objective: To improve the quality of prospective cohorts studying the transition from early stages of back pain to persistent problems, in order to allow researchers to improve the predictive quality, and pool data from multi-centre studies. Summary of background: The progress from early stages of back pain to persistent problems is poorly understood, and only a fraction of the variance at outcome can be accounted for by current prospective cohorts. Standardization of a core set of factors would allow pooling and facilitate comparison between studies. Method: Teams from 12 nations with expertise in clinical practice, prospective cohorts, epidemiology, social sciences, and health services were appointed. The steering committee produced checklists of predictors and outcomes based on systematic reviews and a Delphi focus group. The international teams of experts coded each item for inclusion or exclusion, and recommended new items. This process was iterated twice to resolve disagreement between teams, and to receive scores for new items. The steering committee carried out a consensus synthesis and produced the final lists for predictors and outcome. Finally, the measurements for each factor were selected based on:. original systematic review. recommendations from existing systematic review. Recommendations from consensus statements and narrative reviews. consultation with independent experts. Results: The checklist for predictors include information about demographics, clinical status, psychosocial status, work, and the first consultation for back pain. The recommendation for outcomes include pain, disability, return to work and sick leave, satisfaction, psychological factors, health care utilization and treatment over the follow up period

Recently, the International Consensus Statement Group reported that mechanical prophylaxis with foot-pumps should be considered “Grade A” recommendation for prevention of deep-vein thrombosis after total hip replacement. Mechanical prophylaxis with foot-pumps provides an interesting alternative to chemical agents in the prevention of thomboembolic disease following major orthopaedic surgery procedures. Recent duplex ultrasound studies have suggested that simultaneous use of graduated compression stockings (GCS) may hinder the pneumatic compression effect of foot pumps. The hypothesis of this prospective study was that the use of foot-pumps without GCS does not affect the efficacy of DVT prophylaxis, and improves patient compliance. 846 consecutive patients admitted at a single institution undergoing total hip (THR) or knee replacement (TKR) were included in the study. The A-V Impulse System® foot-pump units (Orthofix Vascular Novame-dix, Andover, UK) was used in all patients. Forty-six patients discontinued the use of foot-pumps, leaving 400 patients who received foot-pumps in combination with GCS and 400 patients with foot pumps alone. Eleven patients of the stocking group (2.7%) and 9 patients of the no-stockings group (2.3%) developed postoperative symptomatic DVT (p=0.07). DVT was more frequent in TKR (10 of 364; 2.7%) than in THR (10 of 436; 2.3%). Non-fatal pulmonary embolism occurred in 4 patients out of 20 with symptomatic DVT, 2 each of the stockings and no stockings groups. The foot pump discontinuation rate of patients treated with stockings was 7%, versus 4% of patients treated without stockings (p< 0.05). In conclusion, management of patients with foot-pumps without GCS does not reduce efficacy of DVT prophylaxis after THR and TKR, and improves patient compliance

Aims

Aseptic loosening is the most common cause of failure following cemented total knee arthroplasty (TKA), and has been linked to poor cementation technique. We aimed to develop a consensus on the optimal technique for component cementation in TKA.

The February 2023 Knee Roundup³⁶⁰ looks at: Machine-learning models: are all complications predictable?; Positive cultures can be safely ignored in revision arthroplasty patients that do not meet the 2018 International Consensus Meeting Criteria; Spinal versus general anaesthesia in contemporary primary total knee arthroplasty; Preoperative pain and early arthritis are associated with poor outcomes in total knee arthroplasty; Risk factors for infection and revision surgery following patellar tendon and quadriceps tendon repairs; Supervised versus unsupervised rehabilitation following total knee arthroplasty; Kinematic alignment has similar outcomes to mechanical alignment: a systematic review and meta-analysis; Lifetime risk of revision after knee arthroplasty influenced by age, sex, and indication; Risk factors for knee osteoarthritis after traumatic knee injury.