Incidental meniscal findings on knee MRI in middle-aged and elderly persons

Englund M, Guermazi A, Gale D, Hunter DJ, Aliabadi P, Clancy M, Felson DT · The New England Journal of Medicine

Meniscal damage — a tear or destruction — was present in 35% of right knees (95% CI 32 to 38), rising with age from 19% (95% CI 15 to 24) among women aged 50 to 59 to 56% (95% CI 46 to 66) among men aged 70 to 90. A tear was more common in knees with pain, aching or stiffness on most days than in knees without, 45% against 26% (P<0.001), but that difference largely goes once radiographic osteoarthritis is accounted for: where radiographic osteoarthritis was present a tear was found in 63% of knees with frequent symptoms and 60% without, adjusted prevalence ratio 1.14 (95% CI 0.90 to 1.45); where it was absent, 32% and 23%, adjusted prevalence ratio 1.43 (95% CI 1.08 to 1.90). Of the tears found, 180 of 297 (61%) were in people who had reported no pain, aching or stiffness in the previous month.

Population

991 ambulatory Framingham residents aged 50 to 90, sampled from census data and random-digit dialling rather than selected for knee problems

Intervention

1.5-tesla MRI of the right knee, with symptoms recorded by questionnaire

Limitations

Cross-sectional prevalence in one community cohort, right knees only and 93% white, with the scans read by one reader and a second consulted where a finding was not definitive (kappa 0.72). It establishes how common a tear is in a knee nobody is complaining about, which is the base rate any imaging finding has to be read against; it says nothing about what happens next.