So the angle itself is more than the type number.
Bowlegs or knock-knees alone do not fully describe knee shape. Femoral and tibial angles and joint-line obliquity also differ. CPAK groups these features into nine types. We asked whether category names or continuous angles better explain later arthritis onset.
2,541 knees without OA were reassessed after 5 years
MOST knees initially below X-ray KL 2 were analyzed. Over 5 years, 480 reached KL ≥2. This defines radiographic onset, not severe pain or surgical need in every case. Alignment change was separately analyzed in knees with follow-up images.
Why do red and blue dots overlap?
The figure shows baseline shapes in knees that did and did not develop OA. The distributions overlap substantially, and CPAK type itself was not significantly associated with onset. Lower JLO, indicating a more oblique joint line, was associated. Recording continuous angles may therefore be more informative for research than type numbers alone.
So 1.36 times the number reads like this.
The group below the data-derived JLO cutoff of 171.6° had 1.36 times the odds of onset compared with the group above it. An odds ratio is not the same as multiplying the probability by 1.36. The number cannot determine from one individual’s X-ray that arthritis will occur. The cutoff needs validation in other populations.
It's not the end of the line that we need to fix the bridge.
An association between shape and OA onset does not prove that surgery on an asymptomatic leg prevents arthritis. Care considers pain, function, previous injury and daily life. The paper identifies more precise candidate markers; research on alignment and actual treatment effects must continue.