title: British athletics muscle injury classification: a reliability study for a new grading system.
abstract: OBJECTIVE
  To implement and validate the newly proposed British athletics muscle injury classification in the assessment of hamstring injuries in track and field athletes and to analyse the nature and frequency of the discrepancies.
  
  
  METHODS
  This was a retrospective study analysing hamstring injuries in elite British athletes using the proposed classification system. Classification of 65 hamstring injuries in 45 high-level athletes by two radiologists at two time points 4 months apart to determine interrater variability, intrarater variability, and feasibility of the classification system was undertaken.
  
  
  RESULTS
  Interrater Kappa values of 0.80 (95% confidence interval [CI]: 0.67-0.92; p<0.0001) for Round 1 and 0.88 (95% CI: 0.76-1.00; p<0.0001) for Round 2 of the review were observed. Percentages of agreement were 85% for Round 1 and 91% for Round 2. The intrarater Kappa value for the two reviewers were 0.76 (95% CI: 0.63-0.88; p<0.0001) and 0.65 (95% CI: 0.53-0.76; p<0.0001) and the average was 0.71 suggesting substantial overall agreement. The percentages of agreement were 82% and 72%, respectively.
  
  
  CONCLUSIONS
  This classification system is straightforward to use and produces both reproducible and consistent results based on interrater and intrarater Kappa values with at least substantial agreement in all groups. Further work is ongoing to investigate whether individual grades within this classification system provide prognostic information and could guide clinical management.
authors.affiliation: Royal Orthopaedic Hospital Foundation Trust, Birmingham, UK. Electronic address: atp194uk@doctors.org.uk.
authors.forename: A
authors.initials: A
authors.lastname: Patel
authors.affiliation: University Hospitals of Bristol, Bristol, UK.
authors.forename: J
authors.initials: J
authors.lastname: Chakraverty
authors.affiliation: British Athletics, London, UK.
authors.forename: N
authors.initials: N
authors.lastname: Pollock
authors.affiliation: British Athletics, Loughborough National Performance Centre, UK.
authors.forename: R
authors.initials: R
authors.lastname: Chakraverty
authors.affiliation: Royal Orthopaedic Hospital Foundation Trust, Birmingham, UK.
authors.forename: A K
authors.initials: AK
authors.lastname: Suokas
authors.affiliation: Royal Orthopaedic Hospital Foundation Trust, Birmingham, UK; Honorary Senior Lecturer, University of Birmingham, UK.
authors.forename: S L
authors.initials: SL
authors.lastname: James
mesh_terms: D001265:Athletic Injuries / Q000145:classification* / Q000175:diagnosis* / Q000473:pathology; D005240:Feasibility Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D018482:Muscle, Skeletal / Q000293:injuries* / Q000473:pathology; D009135:Muscular Diseases / Q000145:classification* / Q000175:diagnosis* / Q000473:pathology; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013177:Sports / Q000706:statistics & numerical data; D014142:Track and Field / Q000706:statistics & numerical data; D006113:United Kingdom