Knee biomechanics walking on railroad ballast and the associated risk factors for knee osteoarthritis

Walking is an important part of everyday life. Osteoarthritis (OA) is a musculoskeletal disorder affecting approximately 20% of adults. The knee is the joint most commonly affected by OA. Knee OA can create severe functional limitations and a decreased quality of life. Walking on crushed rock aggregate is a common and necessary part of the duties of some railroad workers. There is little research describing the increased risks for OA that could be associated with walking on crushed rock aggregate. To measure the external biomechanics at the knee two adjustable tracks were constructed, one with main-line (large) ballast and the other with yard (small) ballast. One of the tracks was modified to represent a normal walking surface. The tracks had an adjustable transverse plane slope. Two slope conditions were used, normal flat condition and 7° sloped condition. Data were collected from 10 railroad workers walking on three surfaces. Data were collected for both conditions on each of the surfaces. Data were collected for both the uphill and downhill knees. Knee kinematic and kinetic data were recorded. The external knee rotation is greatest on large ballast. The knee adduction moments are greatest for the downhill knee on the hard surface sloped condition. The uphill knee has the smallest knee adduction moments. Additional models and further testing are needed to better understand joint loading while walking on crushed rock aggregate.