Occupational kneeling and meniscal tears: a magnetic resonance imaging study in floor layers.

OBJECTIVE: To evaluate the association between occupational kneeling and degenerative meniscal tears.

METHODS: Magnetic resonance imaging (MRI) of both knees was conducted in 92 male floor layers and 49 male graphic designers (referents), with a mean age of 55.6 years (range 42-70 yrs). The presence of grade 3 MRI signal intensities indicating degenerative tears of the anterior, middle, and posterior one-third of the lateral and medial menisci was assessed on 1.5-Tesla MRI scans. The odds ratio (OR) of meniscal tears was determined among floor layers compared to graphic designers. Using logistic regression, models were adjusted for age, body mass index, and knee-straining sports.

RESULTS: Degenerative tears were significantly more prevalent in the medial meniscus among floor layers than among graphic designers [OR 2.28, 95% confidence interval (CI) 1.10-4.98] and significantly more floor layers had medial tears in both knees (OR 3.46, 95% CI 1.41-8.48). Tears extending to the tibial aspect and localized in the middle and posterior one-third of the medial meniscus were most prevalent. Lateral meniscal tears were predominantly unilateral and the prevalence of lateral tears did not differ between the 2 study groups. Knee complaints occurred in about 50% of all floor layers, irrespective of the presence of meniscal tears.

CONCLUSION: Occupational kneeling increases the risk of degenerative tears in the medial but not the lateral menisci in both knees.