title: Epidemiological and clinical outcome comparison of indirect ('strain') versus direct ('contusion') anterior and posterior thigh muscle injuries in male elite football players: UEFA Elite League study of 2287 thigh injuries (2001-2013).
abstract: BACKGROUND
  Data regarding direct athletic muscle injuries (caused by a direct blunt or sharp external force) compared to indirect ones (without the influence of a direct external trauma) are missing in the current literature--this distinction has clinical implications.
  
  
  OBJECTIVE
  To compare incidence, duration of absence and characteristics of indirect and direct anterior (quadriceps) and posterior thigh (hamstring) muscle injuries.
  
  
  METHODS
  30 football teams and 1981 players were followed prospectively from 2001 until 2013. The team medical staff recorded individual player exposure and time-loss injuries. Muscle injuries were defined as indirect or direct according to their injury mechanism.
  
  
  RESULTS
  In total, 2287 thigh muscle injuries were found, representing 25% of all injuries. Two thousand and three were valid for further analysis, of which 88% were indirect and 12% direct. The incidence was eight times higher for indirect injuries (1.48/1000 h) compared to direct muscle injuries (0.19/1000 h) (p<0.01). Indirect muscle injuries caused 19% of total absence, and direct injuries 1%. The mean lay-off time for indirect injuries amounted to 18.5 days and differed significantly from direct injuries which accounted for 7 days (p<0.001). 60% of indirect injuries and 76% of direct injuries occurred in match situations. Foul play was involved in 7% of all thigh muscle injuries, as well as in 2% of indirect injuries and 42% of direct injuries.
  
  
  CONCLUSIONS
  Muscle anterior and posterior thigh injuries in elite football are more frequent than have been previously described. Direct injuries causing time loss are less frequent than indirect ones, and players can usually return to full activity in under half the average time for an indirect injury. Foul play is involved in 7.5% of all thigh muscle injuries.
authors.affiliation: MW Center of Orthopedics and Sports Medicine, Munich, Germany Football Club FC Bayern Munich, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Ueblacker
authors.affiliation: MW Center of Orthopedics and Sports Medicine, Munich, Germany Football Club FC Bayern Munich, Germany.
authors.forename: Hans-Wilhelm
authors.initials: HW
authors.lastname: Müller-Wohlfahrt
authors.affiliation: Football Research Group, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden UEFA Injury Study Group, UEFA Medical Committee, Nyon, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Ekstrand
mesh_terms: D000041:Absenteeism; D001265:Athletic Injuries / Q000453:epidemiology / Q000209:etiology; D003288:Contusions / Q000453:epidemiology / Q000209:etiology*; D005060:Europe / Q000453:epidemiology; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries*; D011446:Prospective Studies; D012008:Recurrence; D000068958:Return to Sport; D012916:Soccer / Q000293:injuries*; D013180:Sprains and Strains / Q000453:epidemiology / Q000209:etiology; D013848:Thigh / Q000293:injuries*; D013997:Time Factors
keywords: Athlete; Football; Muscle; Soccer; Thigh