title: Bone bruise in magnetic resonance imaging strongly correlates with the production of joint effusion and with knee osteoarthritis.
abstract: BACKGROUND
  The findings of magnetic resonance imaging (MRI) have not been studied systematically in patients with osteoarthritis (OA). The objective here was to compare MRI findings with radiological findings in patients with knee pain and to identify factors that influence the progression of OA of the knee.
  
  
  METHODS
  Of 212 patients with knee pain and MRI of the knee joint, 161 patients were selected for the study after exclusion of cases of trauma and other arthritides. MRI was used to evaluate the presence and degree of bone bruise, hydrarthrosis, and injuries to the cruciate ligament and meniscus. Bone bruise was classified into four types, and hydrarthrosis into four grades. Radiologically, OA progression in the femorotibial and patellofemoral joints was analyzed according to the Kellgren-Lawrence classification. Age was divided into four groups based on distribution quartiles. Logistic regression analysis and a generalized linear model with Poisson regression were used to analyze correlations among these factors.
  
  
  RESULTS
  Bone bruise was present in 87 cases, hydrarthrosis in 100, cruciate ligament injury in 20, and meniscus injury in 98. The presence of bone bruise was not related to age, cruciate ligament injury, meniscus injury, nor to OA of the patellofemoral joint, but was related to hydrarthrosis and to OA of the femorotibial joint. Femorotibial OA was much more strongly associated with bone bruise than with hydrarthrosis. Furthermore, analyzing the relation between the types of bone bruise and the degree of hydrarthrosis using a generalized linear model with Poisson regression, there was a positive correlation between the grade of bone bruise and the amount of hydrarthrosis.
  
  
  CONCLUSIONS
  A factor associated with the degree of osteoarthritis of the knee is bone bruise observed on MRI. The degree of hydrarthrosis is related to the grade of bone bruise, but is not linked to the degree of osteoarthritis.
authors.affiliation: Department of Orthopaedic Surgery, Saitama Medical University, Iruma-Gun, Saitama, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Oda
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Igarashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sase
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sase
authors.forename: Seizo
authors.initials: S
authors.lastname: Yamamoto
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D015331:Cohort Studies; D003288:Contusions / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D006833:Hydrarthrosis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D007718:Knee Injuries / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D007867:Leg Bones / Q000293:injuries*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D011859:Radiography; D012307:Risk Factors; D012720:Severity of Illness Index