Published in the December 2008 Coal USA Magazine

Defined as having a coal seam measuring 42 inches or less, lower-seam operations are staffed by crews who face different obstacles to those encountered by miners in standing-height mines. Many arterial functions such as roof bolting, belt repair and supply delivery, literally bring workers to their knees underground, and often for long periods of time.

According to accident statistics from the Mine Safety and Health Administration, more than 50% of all knee musculoskeletal injuries occur in coal mining. Coal miners who suffer knee injuries miss an average of 25 work days, but that figure is a full 10 days longer than the average amount of work missed following a back injury.

The hazard of knee injuries from working within a thin seam mine, the agency noted, has also impacted mines’ recruiting efforts as well as their ability to retain workers.

“Miners working in these lower seams often consider kneepads to be their only line of defense against knee injuries,” a group of researchers at NIOSH said in a recent study, titled Keeping Knees Healthy in Restricted Work Spaces: Applications in Thin Seam Mining.

“However, healthy knees do not start and stop with kneepads.”

There are other ways to stay safe in such environments and prevent injury, according to the group’s study. Proper hygiene and the adjustment of posture can make significant difference, as can a change in work station design.

“Advances in material science and manufacturing methods have occurred since these studies, and further NIOSH efforts in kneepad design are ongoing,” the researchers noted. “However, previous studies did not measure the stresses applied to the knee when kneeling or crawling, which would be very beneficial during the design process.”

NIOSH is currently conducting that very research, but other methods of intervention for injury prevention should also be employed. A very interested mining industry paired with the agency’s increased knowledge of knee injury development brought about NIOSH’s recently released training package intended to help educate workers on reducing their exposure to the risk factors.

“Keeping knees healthy is also a key aspect to reducing costs in low-seam mines as the industry battles rising health care costs, and training/recruitment of replacement workers is time-consuming and costly,” the group said.

The training package is made up of three modules: Symptoms of Knee Injuries, Protect Your Knees While at Work, and Protect Your Knees for a Lifetime. Each focused on workers as a target audience. It was split three ways, the researchers said, so that operators could incorporate one or all of the sections into their annual refresher courses.

“In addition to the training itself, it was also important to reinforce the principles and recommended practices throughout the year,” the group noted, adding that supplemental materials were also developed that may be posted or distributed at appropriate times.

While the agency stressed that it does not endorse any particular option, it suggested several therapies for pain management, including trigger-point massage, low-impact exercise and stretching.

The group also discussed rebound exercise, such as a mini-trampoline or exercise ball, to strengthen leg muscles. “Merely standing on [a] rebounder may be beneficial as the muscles contract to maintain balance and stability.” It added that research on this method is ongoing.

“[The] training package is only a first step toward reducing the risk of knee injuries in low-seam mining,” the NIOSH group said.

“Future research should consider the design and implementation of various interventions that may further reduce this risk.”

One area of research that is vital, the group said, is design of kneepads or some other type of personal protective equipment that can help reduce knee forces and stresses.

“Research in fabrication, materials, and design would also be beneficial since durability, moisture, comfort and resistance to bacteria are a concern.”

NIOSH also cited the need for more work in the equipment design research that may be able to reduce musculoskeletal disorders of the knee.

“Redesign of equipment should focus on reducing twisting at the knee or decreased time spent on one’s knees,” the agency said. “Determining the usefulness of other interventions such as work method changes and job rotation strategies may also be beneficial to the mining industry.”