title: Bone stress injuries causing exercise-induced knee pain.
abstract: BACKGROUND
  No comprehensive studies of bone stress injuries in the knee based on magnetic resonance imaging findings have been published.
  
  
  OBJECTIVE
  Assess the incidence, location, nature, and patterns of bone stress injuries in the knee in military conscripts with exercise-induced knee pain.
  
  
  METHODS
  Case series; Level of evidence, 4.
  
  
  METHODS
  During a period of 70 months, 1330 patients with exercise-induced knee pain underwent magnetic resonance imaging of the knee. A total of 1577 knees were imaged; the images with bone stress injury findings were retrospectively reevaluated with respect to location and type of injury. The person-based incidence of bone stress injuries in the knee was calculated, based on the number of conscripts within the hospital's catchment area.
  
  
  RESULTS
  Of the 1330 patients, 88 (7%) met the inclusion criteria, and 141 bone stress injuries were found in the 110 knees imaged. The incidence of bone stress injuries was 103 per 100 000 person-years. Of the patients, 25% had bilateral bone stress injuries; 28% had 2 solitary bone stress injuries in the same knee simultaneously, all situated in the femoral condyle and tibial plateau. The most common anatomical location for a bone stress injury was the medial tibial plateau (31%), which was also the most typical location for a more advanced injury. After the commencement of military service, a bone stress injury in the medial tibial plateau caused knee pain earlier than did a bone stress injury elsewhere in the knee (P = .014).
  
  
  CONCLUSIONS
  The incidence of bone stress injuries in the knee with exercise-induced knee pain is relatively high in conscripts. Multiple and bilateral injuries can occur. For accurate diagnosis and to ensure appropriate treatment, magnetic resonance imaging is recommended as a routine imaging method when a physical activity can be regularly associated with the onset of symptoms.
authors.affiliation: Research Institute of Military Medicine, Central Military Hospital, Helsinki, Finland.
authors.forename: Maria H
authors.initials: MH
authors.lastname: Niva
authors.forename: Martti J
authors.initials: MJ
authors.lastname: Kiuru
authors.forename: Riina
authors.initials: R
authors.lastname: Haataja
authors.forename: Harri K
authors.initials: HK
authors.lastname: Pihlajamäki
mesh_terms: D000293:Adolescent; D000328:Adult; D015444:Exercise; D005260:Female; D005387:Finland; D015775:Fractures, Stress / Q000175:diagnosis*; D006801:Humans; D007718:Knee Injuries / Q000209:etiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008889:Military Personnel