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- Radiographic classification of osteoarthritis
- Kellgren and lawrence grades of knee osteoarthritis pdf file
- Classifications in Brief: Kellgren-Lawrence Classification of Osteoarthritis
- Joint Space Narrowing and Kellgren-Lawrence Progression in Knee Osteoarthritis
- What Does Osteoarthritis Look Like In The Knee?
Osteoarthritis OA affects more than 21 million people in the U. The prevalence of OA continues to grow as the population ages. Currently available medications for knee OA ameliorate pain without slowing structural progression associated with the disease. Disease modifying osteoarthritis drugs DMOADs are still in early stages of development and testing 4.
Magnetic resonance imaging MRI may eventually eclipse plain radiography as the modality of choice for documenting structural progression in OA. However, the interpretation of cartilage findings on MRI is still evolving and plain radiography remains the standard method for assessing progression.
The measurement of radiographic joint space width is the most accepted and widely-used method of assessing OA progression. As it has been shown to be sensitive to change 5 , joint space narrowing has remained the primary outcome by which DMOAD trials have tested drug efficacy so far 6 , 7.
Yet, the rate of joint space narrowing among cohorts with knee OA exhibits variability 8 - 10 , potentially stemming from differences caused by changing patient characteristics and clinical status over time, inconsistent radiographic positioning of the knee during serial x-ray visits, and other technical factors 8. With the promise of effective DMOAD therapy on the horizon, it is crucial to establish factors affecting the rate of joint space narrowing across various study settings.
Another common metric of OA progression is the Kellgren-Lawrence scale, traditionally used to assess the severity of radiographic knee OA. This categorical scale incorporates important radiographic features of OA joint space narrowing and osteophyte development into one scale of increasing severity The use of the Kellgren-Lawrence scale has been criticized because its individual categories are not equidistant from each other Consequently, estimates of the proportion of patients that progress from one category to the next may not be comparable for all starting points.
Since the Kellgren-Lawrence scale is still used in clinical settings for making treatment decisions, its value in assessing knee OA progression warrants continued investigation.
The goal of this analytic review is to describe the variability in estimates of knee OA progression joint space narrowing and Kellgren-Lawrence from the published literature and to identify factors explaining this variability. The potential predictors we examined included study and technical factors study design, year of study publication, study duration, sample size, reader reliability assessment, radiographic definition of OA, radiographic approach used , and cohort characteristics age, gender, body mass index BMI , baseline joint space width, and OA-related cohort composition.
We conducted a search of the PubMed database for relevant studies published between January and October We used the key words osteoarthritis and knee , in combination with one or more of the following: progression or change , radiograph or x-ray , joint space narrowing and Kellgren-Lawrence. The first author screened through abstracts identified by the search.
For abstracts that assessed joint space narrowing, we included for further review those studies in which the patient sample had evidence of knee OA, progression was assessed radiographically over time, and sample size was greater than For abstracts that assessed joint space narrowing, we included studies in which the patient sample had evidence of knee OA, progression was assessed radiographically over time, and sample size was greater than Abstracts that analyzed Kellgren-Lawrence progression and examined OA incidence were also eligible for inclusion.
We excluded literature reviews and studies not published in English. For abstracts that passed this screening, we retrieved the full length articles. For inclusion in our study, the manuscript had to report either change in joint space width over a specified period of time or the proportion of the population that progressed in Kellgren-Lawrence grade over a specified period.
Studies that exclusively assessed osteophyte progression, used categorical scales of OA severity other than Kellgren-Lawrence, and reported proportion of population that experienced joint space narrowing rather than differences in means were excluded.
We extracted the following study and technical factors: study design observational or randomized control trial RCT , year of publication, whether radiograph reader reliability tests were conducted or cited, sample size, length of follow-up, and radiographic view used. Year of publication was included to address potential secular trends in radiographic methods. We also extracted descriptive characteristics of the study population, including proportion female, mean age, mean BMI and mean baseline joint space width defined as the smallest interbone distance across the knee joint 6.
We also extracted data pertinent to the two main outcomes: 1 change in joint space width over the follow-up period and 2 proportion of the study population that progressed at least one Kellgren-Lawrence grade over the follow-up period. We refer to the latter as the risk of Kellgren-Lawrence progression. Estimates of change in joint space width over the follow-up period referred to as joint space narrowing throughout this report were converted to annual rates.
Similarly estimates for Kellgren-Lawrence progression were converted to annual risks of progression. For studies that reported estimates of progression for multiple cohorts, we included all estimates in our analyses. For studies that reported on change at various intervals in the same patients, only the estimate from the longest follow-up time was included.
For RCTs, we extracted data from the placebo arm only. For studies that reported change in Kellgren-Lawrence scale in each left, right knee individually, we used estimates for the right knee only. For the joint space narrowing analysis, we grouped the 5 radiographic approaches observed in the literature into 3 categories: 1 full extension included the standing AP view, 2 semi-flexed with fluoroscopy included the semiflexed AP and Lyon Schuss views, and 3 semi-flexed without fluoroscopy included the MTP and fixed-flexion PA views.
Since only one study assessing Kellgren-Lawrence progression used fluoroscopic methods, we collapsed the three radiographic approach categories to include only full extension and semi-flexed. To avoid double-counting these cohorts, we ran two separate Kellgren-Lawrence models.
Both models included all Kellgren-Lawrence estimates from manuscripts that define OA either way, but not both. We performed meta-regression analyses examining the effects of radiographic approach, study design, year of study publication, length of follow-up, whether reader reliability was tested, and cohort characteristics such as mean age and proportion female, on each outcome: joint space narrowing or Kellgren-Lawrence progression.
In addition, for the joint space narrowing model, we included mean baseline joint space width and mean BMI as predictors. For the Kellgren-Lawrence models, we included OA definition and cohort composition. We then examined various hypothesis-driven interactions in all models.
In both the joint space narrowing and Kellgren-Lawrence models, observations were weighted by the sample size of the cohort from which the observation was derived.
The results of the search are depicted in Figure 1. Of manuscripts identified through our PubMed search, 34 both met the inclusion criteria and did not meet the exclusion criteria. These 34 studies comprise the study sample.
All studies had a greater proportion of females than males. Fifteen estimates were derived from RCTs, and the remaining 12 were derived from observational studies. Eleven out of 27 estimates used full extension radiographic approach; eight used semi-flexed approach without fluoroscopy; and eight used semi-flexed approach with fluoroscopy see Figure 2. Joint space narrowing estimates ranged from The mean annual joint space narrowing across all estimates was 0.
Annual joint space narrowing stratified by study design and radiographic approach. Circles represent individual mean joint space narrowing estimates.
Circle area is proportional to sample size of corresponding cohort. Means within study design and radiographic approach sub-categories are depicted in grey. Overall means within each study design category and the overall mean for all estimates are depicted in black.
Each study reference is denoted next the circle, representing the corresponding manuscript from which the progression estimate was derived.
An estimate of 0. Overall, observational studies had a mean rate of joint space narrowing of 0.
Adjusted mean rates of joint space narrowing were similar for full extension across both study designs 0. Observational studies that used either semi-flexed approach reported larger narrowing estimates compared to RCTs that used the same approach. We did not find a statistically significant association between radiographic approach and joint space narrowing among observational studies. However, among RCTs, full extension was associated with greater narrowing compared to the semi-flexed without fluoroscopy approach.
We found no statistically significant difference in narrowing between full extension and semi-flexed with fluoroscopy among RCTs, but the minimal overlap in confidence intervals between the two groups is suggestive of a difference see Figure 2.
We did not find an association between rates of joint space narrowing and mean age, mean BMI, reader reliability, and year of publication. Baseline joint space width was highly correlated with study design and radiographic approach, and thus was not included in the final model. Circles represent individual estimates of the proportion of the cohort that progressed by at least one Kellgren-Lawrence grade per year of follow-up time.
Regression line for follow-up time is weighted for sample size and adjusted for radiographic approach 4A and 4B , OA definition 4B , and cohort composition 4B.
Eleven out of 13 studies were observational studies, and the remaining two were RCTs. Ten out of 13 used full extension radiographic approach, while the remaining three used semi-flexed approach. The annual estimates of progression by at least one Kellgren-Lawrence grade ranged from 1.
As seen in Figure 4B , a negative linear relationship exists between risk of Kellgren-Lawrence progression and follow-up time. We did not find an association between Kellgren-Lawrence progression and radiographic approach, gender, age, year of publication, study design, or reader reliability.
Radiographic classification of osteoarthritis
Annual risk of Kellgren-Lawrence progression stratified by cohort composition. Means within each cohort composition category are depicted in grey. Overall mean for all reviewed Kellgren-Lawrence studies is depicted in black. Multivariate findings were similar in both models, except for the effect of radiographic approach. The goal of this analytic review was to describe the variability in estimates of knee OA progression joint space narrowing and Kellgren-Lawrence from the published literature and to identify factors explaining this variability.
We performed a thorough systematic search and analytic synthesis of the published peer-reviewed literature on radiographic progression of knee osteoarthritis.
Kellgren and lawrence grades of knee osteoarthritis pdf file
Using these sources, we derived estimated annual rates of joint space narrowing and risks of Kellgren-Lawrence progression in populations with knee OA. We used meta-regression to study the association of these measures of OA structural progression with cohort characteristics and study features, in an attempt to explain the variability in estimates.
A better understanding of the true rate of progression would assist clinicians in providing patients with an evidence-based trajectory of disease and timing of appropriate treatments. We found a mean rate of joint space narrowing of 0.
Classifications in Brief: Kellgren-Lawrence Classification of Osteoarthritis
This value falls within the range reported by other investigators. Pavelka et al. Our finding is also consistent with the range reported by Vignon et al.
Secondly, we found a mean annual risk of progression in Kellgren-Lawrence grade of 5.
Joint Space Narrowing and Kellgren-Lawrence Progression in Knee Osteoarthritis
To the best of our knowledge there are no published reports summarizing OA progression based on Kellgren-Lawrence grade. Both metrics exhibited variability, with standard deviations similar to the means. This is the first literature review to our knowledge that comprehensively reports OA progression estimates and attempts to quantitatively explain the variability inherent in these estimates, adjusting for important covariates.
What Does Osteoarthritis Look Like In The Knee?
To rigorously investigate these questions, we also used weighted regression techniques, which helped to eliminate the effect of sample size on the parameter estimates. We demonstrated that estimates of joint space narrowing exhibit variability, partly explained by differences in radiographic approach and study design see Figure 2.
We found that among observational studies, those that used full extension approach, while not statistically significant, tended to report lower estimates of narrowing than those that used either semi-flexed approach. This is consistent with findings by Wolfe et al. No difference was reported between the Lyon Schuss view and the MTP view, further supporting our finding that the use of fluoroscopy in the semi-flexed approach has little impact on the joint space narrowing estimates see Figure 2