title: Epidemiology of intra- and peri-articular structural injuries in traumatic knee joint hemarthrosis - data from 1145 consecutive knees with subacute MRI.
abstract: In patients with traumatic knee distorsion and hemarthrosis, to investigate the panorama of structural injury, as visualized on magnetic resonance imaging (MRI).
  
  
  
  Cohort study of 1145 consecutive patients with traumatic knee distorsion who underwent MRI within median 8 days after injury. We present structural injury as visualized on MRI in relation to age, sex and activity at injury. Population based gender specific annual incidences of common structural injuries were calculated.
  
  
  
  The majority of injuries (72%) occurred during sports. Overall, anterior cruciate ligament (ACL) rupture was the most common structural injury (52%), followed by meniscal tear (41%) and lateral patella dislocation (LPD, 17%). Only 12% of ACL tears were isolated with meniscal tear being the most common associated injury (55%). The annual incidence of ACL injury was 77 (70-85, 95% CI) per 100,000 inhabitants with significant differences between men (91, 80-103) and women (63, 53-73). In those aged 16 years and younger, LPD was the most frequent structural injury, both in boys (39%) and girls (43%). In this age group, the annual incidence of LPD was 88 (68-113) and higher in boys (113, 81-154) than in girls (62, 39-95).
  
  
  
  ACL injury occurs in one out of two knees with traumatic hemarthrosis but only 12% are without concomitant structural injury. The overall rate of traumatic knee hemarthrosis and ACL injury is higher in men. In those aged 10-19 years, ACL rupture is more common among girls than boys whereas in those 16 years and younger, LPD is more common among boys than girls.
authors.affiliation: Department of Orthopedics, Helsingborg Hospital, Helsingborg, Sweden. Electronic address: ola.a.olsson@skane.se.
authors.forename: O
authors.initials: O
authors.lastname: Olsson
authors.affiliation: Department of Orthopedics, Helsingborg Hospital, Helsingborg, Sweden. Electronic address: anders.isacsson@skane.se.
authors.forename: A
authors.initials: A
authors.lastname: Isacsson
authors.affiliation: Clinical Epidemiology Unit, Orthopedics, Department of Clinical Sciences Lund, Lund University, Lund, Sweden; Clinical Epidemiology Research & Training Unit, Boston University School of Medicine, Boston, MA, USA. Electronic address: martin.englund@med.lu.se.
authors.forename: M
authors.initials: M
authors.lastname: Englund
authors.affiliation: Department of Orthopedics, Helsingborg Hospital, Helsingborg, Sweden; Orthopedics, Department of Clinical Sciences Lund, Lund University, Lund, Sweden. Electronic address: richard.frobell@skane.se.
authors.forename: R B
authors.initials: RB
authors.lastname: Frobell
mesh_terms: D015331:Cohort Studies; D005260:Female; D006395:Hemarthrosis; D006801:Humans; D007718:Knee Injuries; D007719:Knee Joint; D008279:Magnetic Resonance Imaging; D008297:Male
keywords: ACL injury; Epidemiology; Hemarthrosis; MRI; Patella dislocation