Hi, some info on how OA was graded before and how it is now, plus some thoughts on what they're considering for the future:
From a National Institutes of Health (US)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3339535/ paper.
Describing how OA was graded in patients before:
Kellgren (1963) described 4 grades of hip OA:
- grade 1 (doubtful OA), possible narrowing of the joint space medially and possible osteophytes around femoral head
- grade 2 (mild OA), definite narrowing of the joint space inferiorly, definite osteophytes, and slight sclerosis
- grade 3 (moderate OA), marked narrowing of the joint space, slight osteophytes, some sclerosis and cyst formation, and deformity of the femoral head and acetabulum
- grade 4 (severe OA), gross loss of joint space with sclerosis and cysts, marked deformity of the femoral head and acetabulum, and large osteophytes
This was then updated to what is accepted now as the mode used to grade OA:
Croft et al. (1990) graded OA into 5 categories:
- grade 1, osteophytosis only
- grade 2, joint space narrowing only
- grade 3, two of osteophytosis, joint space narrowing, subchondral sclerosis, and cyst formation
- grade 4, three of the same features as above
- and grade 5, as in grade 4 but with deformity of the femoral head
And this is currently the thought on joint space narrowing:
Joint space width (JSW) was measured in the upper, weight-bearing part of the joint according to Jacobsen and Sonne-Holm (2005). The shortest distance between the femoral head and acetabulum was measured at 3 locations: the lateral and medial margins of the subchondral sclerotic line (sourcil) and along the vertical line through the center of the femoral head. The minimum JSW was used for diagnosis of OA. If minimum JSW was outside the 3 standard locations, an additional measurement at the site of maximum narrowing was performed. The definition of OA is a minimum JSW of less than 2.0 mm. In order to perform an intra-observer analysis, observer 2 repeated the assessments of OA more than 3 weeks after the first assessments.
That is how things stand now in how we were diagnosed and weighed for the grade of OA. There is some discussion that there are too many grades, and they can be simplified. From the same study:
"The K&L classification has 5 grades and the Croft has 6 grades including normal, doubtful, mild, moderate, and severe OA. A modification, reducing the number of grades, would make these classifications easier to use and would improve their reliability. Since Danielsson (1967) found that osteophytes alone are not a sign of OA, grade 1 of the K&L classification (“possible osteophytes”) and grade 1 of the Croft classification (“osteophytosis only”) could be included in the group with no OA. Grade 2 in the Croft grading “joint space narrowing only” is difficult to interpret, because there is no information about how much the joint space should be reduced and it is very rare to have a substantially reduced joint space without other signs of OA. Thus, grade 2 could be combined with grade 3 and called mild OA. The 2 highest grades, 3 and 4 by K&L and 4 and 5 by Croft, could also be combined and termed severe OA, because the distinction between them seems to be rather unimportant from a clinical point of view."
Their opinion is that the best way to test for OA is by Joint Space Width method. Their statistical analysis found that to be a more reliable way to detect existing OA than the grades. Quoting them:
"JSW measurements had good accordance with gradings based on global visual assessment. Thus, comparison of long-term studies of DDH patients could be sufficiently reliable, even if different OA classifications have been used. This indicates that the K&L and Croft gradings could still be used, but the categories should be as few as possible and should not exceed 3: no OA, mild OA, and severe OA. However, since the JSW classification is the most reproducible and also the simplest and fastest, this appears to be the preferred method for future studies, especially in DDH where the most important location of the joint is the upper weight-bearing part. Moreover, minimum JSW had a closer association with pain than the K&L and Croft classifications (Jacobsen et al. 2004). Digital measurements directly on the screen with 4 times enlargement of the radiograph adds to the convenience of the JSW method. Digital measurements have been found to be more accurate than traditional manual measurements on hard copies of radiographs (Conrozier et al. 1997).
Even if a hip has no OA by the minimum JSW method, global visual assessment can show severe OA (K&L grades 3–4 and Croft grades 4–5). Although this rarely occurs, such hips should probably be added to those classifed as OA by the minimum JSW method, giving the true total frequency of OA.
In conclusion, the minimum JSW method is the simplest and most reliable classification when grading the presence of hip OA in long-term studies of patients with DDH. A classification based on global visual assessment can be used in addition if only the severe grades of OA are included in the abnormal hips."
Sorry for the length of the post, but this caught my attention.
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