The risk of developing osteoarthritis within the knee tibiofemoral (TF) joint increased with trade seniority (number of working years) among floor layers when compared to a control group of graphic designers in a recent Danish study involving 254 subjects. This finding suggests a dose-response relationship between knee TF degenerative changes and long duration kneeling, which is considered to be the position assumed approximately 50 percent of the time among floor layers.
The study also found that floor layers aged 50-59 had a 3.6 greater chance of having arthritic changes along the knee TF joint compared to similar aged graphic designers. The prevalence of the degenerative disorder, determined through radiographic assessment, was twice as high in the medial TF joint space for floor layers as opposed to graphic designers within this age group. Researchers reported that outside this age range, no significant difference involving TF arthritic changes was seen between these two occupational groups.
Evaluation of the knee patellofemoral (PF) joint space disclosed a marginally greater prevalence of arthritic changes among 50-59-year-old floor layers relative to same-aged graphic designers. PF arthritic development was slightly more common among graphic designers in other age groups (≤ 49 and ≥ 60 years of age).
The study involved 134 floor layers and120 graphic designers. Overall, radiographic knee osteoarthritis was identified among 61 (24 percent) of the subjects.
The Bottom Line – How This Applies To Ergonomists
The postural position of long duration kneeling increases the risk of developing knee arthritis along the medial aspect of the tibiofemoral joint. Also, a dose-response relationship seems to exist.
No association was identified between long term kneeling and arthritic changes at the knee patellofemoral joint. The authors felt the small size of the study may have clouded this finding.
Other Key Study Points
The researchers concluded that selection bias may have contributed to some of the unanticipated findings (i.e., lack of higher prevalence of TF arthritic development floor layers in the younger and older age groups).
Among the two occupational groups, there was diversity regarding which knee/compartment was affected by arthritic changes:
- Isolated TF changes were seen among 19 (14.2 percent) floor layers and 9 (7.5 percent) graphic designers
- Isolated PF changes were seen among 9 (6.7 percent) floor layers and 15 (12.5 percent) graphic designers
- Combined TF and PF changes were seen in 3 (2.2 percent) floor layers and 6 (5.0 percent) graphic designers
There was no significant difference, either within or between the two groups, in the incidence of arthritic changes when comparing the right and left knees.
Workers with knee pain tended to have a higher participation in the study.
A questionnaire was distributed to 286 male floor layers and 370 male graphic designers that yielded a return of 88 percent and 78 percent respectively. From these cohort groups, those with a history of knee joint fractures meniscus disorders and cruciate ligament ruptures were eliminated. Obtaining informed consent for radiographs reduced the study group further to 134 floor layers and 120 graphic designers.
The two groups were stratified for age (≤ 49, 50-59, and ≥60).
Radiographs were taken in the standing position and one leg weight-bearing position with the knee in 20-30 degree flexion. Views included postero-anterior, lateral and axial patellofemoral exposures.
The radiographs were read by one radiologist, who examined the medial and lateral joint spaces of the tibiofemoral and patellofemoral compartments using a modified Ahlbäck scale of joint space narrowing. Reliability was established through a intra-reader reevaluation.
Controls were made for body mass index and a history of knee-straining sporting activities.
This complete paper can be acquired at: http://www.occup-med.com/content/4/1/19
Article Title: Occupational kneeling and radiographic tibiofemoral and patellofemoral osteoarthritis
Publication: Journal of Occupational Medicine and Toxicology, 4(19), 2009
Authors: S Rytter, N Egund, L K Jensen, and J P Bonde
This article originally appeared in The Ergonomics Report™ on 2009-12-02.