Proper Postures Prevent Knee Injury
Introduction
The knee is an extremely unique and versatile joint in the body. Because of this, there are many potential injuries that can arise throughout a range of different postures. For example, excessive kneeling can lead to bursitis, an inflammation of the tissue that lubricates the knee1. Ligament sprains and muscle strains can occur with excessive twisting or poor posture in movements with high forces2. Chronic malalignment of the knee can also lead to patellofemoral pain, tendinitis, and osteoarthritis, which cause pain with knee movements3. Sudden impacts on the knee can lead to fractures or dislocations depending on the direction of the impact1. These are only a few of the common injuries that can impact the knee and its surrounding tissues.
Prevalence
These knee injuries commonly occur in the workplace, when demands are placed on workers that predispose them to injury. According to the workplace safety insurance board of Ontario, 15.4% of all injuries that caused lost work time in 2020 were caused by injuries to the lower body4. Of these lower body injuries, over half of them were projected to have been caused by knee related traumas5. This is important as knee injuries often take a long time to heal, with sprains and strains often sidelining workers for 2-4 weeks and major traumas taking anywhere from 4-12 months to heal6.
Prevention
One way to avoid a workplace injury of the knee is to avoid dangerous postures that increase the risk of such an injury and replace those movements with biomechanically safer and more stable movements. Most workplaces can be modified to reduce risk of knee injury.
1 - Lifting and Bending
Lifting can be one of the most dangerous activities for the knee, as it typically involves large forces. However, lifting in proper posture can take advantage of the anatomy of the knee and prevent most common knee-related injuries7.
- When lifting, it is extremely important to keep the lower leg perpendicular to the floor. If the knee caves inwards while lifting, as seen below, it can cause an acute strain or sprain or cause long term osteoarthritis3.
- Keeping the knee over the toes also can help prevent injury, as this trick can help distribute the weight evenly forward and backward to maintain balance3.
- Lastly, it is important to avoid twisting the knee while lifting as twisting puts excess strain on soft tissue surrounding the knee5.
2 - Walking or Carrying a Load
Standing and walking with a load are common activities in the workplace that can also impact knee health.
- Ensure that your legs are in line with your hips and that your thigh is in the same line as your lower leg. This ensures that your weight is being transferred straight down your leg in a safe manner5.
- Ensure that your toes are pointed in the direction of your upper body. When your toes point significantly outwards or inwards, it can cause a dangerous twists at the knee5.
3 - Sitting at a Desk
Many of today’s workplaces involve office work that typically requires a seated position for many consecutive hours. A poor seated posture can slowly wear away at knee health and eventually lead to injury.
- Keep your knees between a 90° and 130° angle
- If your chair is too high and your knees are at a much larger angle of over 130 degrees, this can put pressure on blood vessels in the thigh and impair blood flow8.
- If your chair is too low and your knees are at less than 90 degrees, your thighs may not be supported by the chair and this will put more pressure in one place8.
(Photo from https://www.msdprevention.com/Quick-Start-Guideline-Office.htm)
4 – Ground Work
Some jobs may require work to be competed on or near ground level. Protecting the knees is critical in these situations as there are many potential knee injuries that can occur from working at or near the ground.
- Avoid kneeling for long periods of time, and periodically switch between seated positions.
- When kneeling, use a knee pad or knee creeper to spread out the force across the knee9.
- Additionally, consider placing a knee saver pad on the back of your heels to reduce the bend in your knees when kneeling for long periods of time, particularly if you are working on a sloped surface9.
Conclusion
Knee pain can be prevented through the use of ergonomic postures that reduce stress on various structures in the knee. Individualized MSD prevention plans can help apply these tips and more in the workplace to prevent knee injuries and reduce lost time. Additionally, these MSD prevention plans can further supplement these safe postures by introducing task specific warm-ups and dynamic stretches to increase blood flow to the knee and further reduce injury risk. Overall, a large percent of the occupational knee-related injuries in Ontario are preventable through the use of ergonomics and MSD prevention plans.
References
1Williams, C. H., Jamal, Z., & Sternard, B. T. (2021). Bursitis. In StatPearls. StatPearls Publishing.
2Kakarlapudi, T. K., & Bickerstaff, D. R. (2001). Knee instability: isolated and complex. The Western journal of medicine, 174(4), 266–272. https://doi.org/10.1136/ewjm.174.4.266
3Felson, D. T., Niu, J., Gross, K. D., Englund, M., Sharma, L., Cooke, T. D., Guermazi, A., Roemer, F. W., Segal, N., Goggins, J. M., Lewis, C. E., Eaton, C., & Nevitt, M. C. (2013). Valgus malalignment is a risk factor for lateral knee osteoarthritis incidence and progression: findings from the Multicenter Osteoarthritis Study and the Osteoarthritis Initiative. Arthritis and rheumatism, 65(2), 355–362. https://doi.org/10.1002/art.37726
4By the numbers: Open data downloads. (2021). WSIB. https://www.wsib.ca/en/numbers-open-data-downloads
5Positioning the Body to Reduce MSD Injury Risk: Focus on the Knee. (2021). Centre of Research Expertise for the Prevention of Musculoskeletal Disorders. https://www.msdprevention.com/resource-library/positioning-the-body-to-reduce-msd-injury-risk-focus-on-the-knee.htm
6Klein, N. (2021, July 29). Recovering from a Knee Injury. ANOVA IRM Stem Cell Center. https://anova-irm.com/en/media-information-news/research-news-blog/recovering-from-a-knee-injury
7Klussmann, A., Gebhardt, H., Nübling, M., Liebers, F., Quirós Perea, E., Cordier, W., von Engelhardt, L. V., Schubert, M., Dávid, A., Bouillon, B., & Rieger, M. A. (2010). Individual and occupational risk factors for knee osteoarthritis: results of a case-control study in Germany. Arthritis research & therapy, 12(3), R88. https://doi.org/10.1186/ar3015
8Working in a Sitting Position - Good Body Position : OSH Answers. (2017). Canadian Center for Occupational Health and Safety. https://www.ccohs.ca/oshanswers/ergonomics/sitting/sitting_position.html
9Breloff, S. P., Dutta, A., Sinsel, E. W., Carey, R. E., Warren, C. M., Dai, F., Ning, S., & Wu, J. Z. (2019). Are knee savers and knee pads a viable intervention to reduce lower extremity musculoskeletal disorder risk in residential roofers?. International journal of industrial ergonomics, 74, 10.1016/j.ergon.2019.102868. https://doi.org/10.1016/j.ergon.2019.102868