Trends in knee magnetic resonance imaging.
OBJECTIVE
To assess trends in knee magnetic resonance imaging (MRI) use and accompanying management changes to determine whether indications for this test have changed over time.


METHODS
Large administrative database containing health care information for 587,010 people living in 1 state who were enrolled in the Medicare or Medicaid programs. They all had used health services during 3 consecutive years between 1991 to 1995.


METHODS
We performed a retrospective cohort study examining the rates of lower extremity MRI in successive years and calculated the proportion of patients who were seen by a knee specialist or underwent knee surgery subsequent to the MRI.


RESULTS
The annual rate of knee MRI was 1.4 per 1000 person-years in 1991 and increased by 140% to 3.4 per 1000 person-years by 1995 (P = 0.001). Approximately half of patients who underwent a knee MRI in 1991 had a diagnosis of internal derangement of the knee in the prior year; this figure dropped to 35% in 1995 (P < 0.001). The percentage of patients undergoing a knee MRI who had no record of any knee diagnosis in the prior year grew from 13% in 1991 to 33% in 1995 (P < 0.001). Over the 5 years of the study, the percentage of patients whose knee MRI was followed by specialist care or knee surgery decreased from 68% to 58%, a relative change of 15% (P < 0.005).


CONCLUSIONS
Knee MRI use increased sharply during the study period, but the proportion of such patients who had a prior diagnosis of internal derangement or subsequently saw a knee specialist or underwent knee surgery decreased. This finding indicates that the criteria for knee MRI appear to have broadened substantially during this period.
Division of Pharmacoepidemiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. dhsolomon@partners.org
Daniel H
DH
Solomon
Jeffrey N
JN
Katz
John A
JA
Carrino
Jonathan L
JL
Schaffer
Rhonda L
RL
Bohn
Helen
H
Mogun
Jerry
J
Avorn
D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007717:Knee / Q000473:pathology* / Q000601:surgery; D007719:Knee Joint / Q000473:pathology / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008297:Male; D008484:Medicaid; D006278:Medicare; D008875:Middle Aged; D009515:New Jersey; D012189:Retrospective Studies; D013673:Technology Assessment, Biomedical; D014481:United States; D014600:Utilization Review