Occupation-Related Squatting, Kneeling, and Heavy Lifting and the Knee Joint: A Magnetic Resonance Imaging-Based Study in Men

SHREYASEE AMIN, JOYCE GOGGINS, JINGBO NIU, ALI GUERMAZI, MIKAYEL GRIGORYAN, DAVID J. HUNTER, HARRY K. GENANT, and DAVID T. FELSON

ABSTRACT.

Objective. We examined the relation between occupational exposures to frequent squatting/kneeling and/or heavy lifting with cartilage morphology, based on magnetic resonance imaging (MRI), at the tibiofemoral and patellofemoral joints in men and determined which compartments are most affected.

Methods. We evaluated 192 men with symptomatic knee osteoarthritis (OA). The more symptomatic knee was imaged using MRI. Cartilage was scored using the Whole Organ MRI Score semiquantitative method at the medial and lateral tibiofemoral joint and patellofemoral joint. Occupational exposures to frequent squatting, kneeling, and/or heavy lifting were assessed using a validated questionnaire.

Results. Among the 192 men [mean (± standard deviation) age 69 ± 9 yrs, body mass index (BMI) 30.8 ± 4.7 kg/m²], those reporting occupational exposure to squatting/kneeling alone, heavy lifting alone, both squatting/kneeling and heavy lifting, or none of these activities numbered 7, 40, 47, and 98, respectively. Compared with men with no occupational exposure to these activities, and following adjustment for age, BMI, and history of knee injury or surgery, we found that men reporting occupational exposures to both squatting/kneeling and heavy lifting had a modest increased risk for worse cartilage morphology scores at the patellofemoral joint [odds ratio (OR) 1.8, 95% confidence interval (CI) 1.1 to 3.2] and medial tibiofemoral joint (OR 1.6, 95% CI 0.9, 3.0), although the latter did not reach statistical significance.

Conclusion. Men with frequent occupational squatting/kneeling and heavy lifting have a greater likelihood for worse cartilage morphology scores at the patellofemoral joint. These findings add support to the important role of biomechanical loading on the pathogenesis of knee OA, particularly patellofemoral OA. (First Release July 1 2008; J Rheumatol 2008;35:1645–9)

Key Indexing Terms:

OCCUPATIONAL DISEASES
KNEE OSTEOARTHRITIS
CARTILAGE
MAGNETIC RESONANCE IMAGING
PATELLA

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From the Division of Rheumatology, College of Medicine, Mayo Clinic, Rochester, Minnesota; Clinical Epidemiology Research and Training Unit and Arthritis Center, Boston University School of Medicine; Department of Radiology, Boston University School of Medicine, Boston, Massachusetts; Department of Neurology, University of Iowa, Iowa City, Iowa; Department of Radiology, University of California at San Francisco; and Synarc, San Francisco, California, USA.

Supported by an Osteoarthritis Biomarkers Grant from the Arthritis Foundation; National Institutes of Health grant AR47785; and a grant from the Bayer Corporation.

S. Amin, MDCM, MPH, Division of Rheumatology, College of Medicine, Mayo Clinic; J. Goggins, MPH; J. Niu, MD, DSc; D.J. Hunter, MBBS, PhD; D.T. Felson, MD, MPH, Clinical Epidemiology Research and Training Unit and Arthritis Center; A. Guermazi, MD, Department of Radiology, Boston University School of Medicine; M. Grigoryan, MD, Department of Neurology, University of Iowa; H.K. Genant, MD, Department of Radiology, University of California at San Francisco, and Synarc.

Address reprint requests to Dr. S. Amin, Division of Rheumatology, College of Medicine, Mayo Clinic, Rochester, MN 55905. E-mail: amin.shreyasee@mayo.edu

Accepted for publication March 20, 2008.

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