Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2010 Nov;62(11):1527-32.
doi: 10.1002/acr.20287. Epub 2010 Jul 8.

Methodologic challenges in studying risk factors for progression of knee osteoarthritis

Yuqing Zhang  1 , Jingbo Niu, David T Felson, Hyon K Choi, Michael Nevitt, Tuhina Neogi
Affiliations
Review

Methodologic challenges in studying risk factors for progression of knee osteoarthritis

Yuqing Zhang et al. Arthritis Care Res (Hoboken). 2010 Nov.
No abstract available

PubMed Disclaimer

Figures

Figure 1
Figure 1
A causal diagram of a randomized trial showing assessment of the effect of an intervention regimen (e.g., weight loss) on the risk of ROA progression. Because the intervention regimen in this trial is randomly assigned to the study participants, the intervention regimen is not influenced by either potential confounders (e.g., age, sex, genetic factors, etc.) or previous ROA status, as indicated by the absence of arrows or causal paths directed towards the intervention regimen.
Figure 2
Figure 2
A causal diagram of an observational study showing the assessment of the effect of obesity on ROA progression among knees with preexisting ROA at baseline. Conditioning on baseline ROA results in its causes (i.e., obesity and the genetic factor) becoming directly associated, as indicated by a dotted line between obesity and genetic factors, even though these two factors are not associated before the knees developed ROA. Such conditioning opens an alternative path from obesity to ROA progression (i.e., obesity --- genetic factor → ROA progression), thus biasing the effect of obesity on ROA progression.
Figure 3
Figure 3
A causal diagram of an observational study showing the assessment of the effect of obesity on ROA progression among knees that have preexisting ROA at baseline and also have follow-up knee radiographs. Conditioning on a common effect, i.e., complete follow-up status (obesity → complete follow-up ← ROA progression) results in its causes (i.e., obesity and ROA progression) becoming directly associated, and opens an alternative path from obesity to ROA progression (i.e., obesity --- ROA progression). Thus, even if there is no association between obesity and ROA progression, conditioning on complete follow-up status tends to introduce a negative association between obesity and ROA progression.
See this image and copyright information in PMC

Comment in

References

    1. Neogi T, Felson D, Niu J, et al. Association between radiographic features of knee osteoarthritis and pain: results from two cohort studies. Br Med J. 2009;339:b2844. - PMC - PubMed
    1. Guccione AA, Felson DT, Anderson JJ, et al. The effects of specific medical conditions on the functional limitations of elders in the Framingham Study. Am J Public Health. 1994;84:351–8. - PMC - PubMed
    1. DeFrances CJ, Podgornik MN. 2004 National Hospital Discharge Survey. Adv Data. 2006:1–19. - PubMed
    1. Felson DT. Chondroitin for pain in osteoarthritis. Ann Intern Med. 2007;146(8):611–2. - PubMed
    1. Zhang Y, Jordan JM. Epidemiology of osteoarthritis. Rheum Dis Clin North Am. 2008;34:515–29. - PMC - PubMed

Publication types

LinkOut - more resources