Abstract: Objective To study the relationship between knee osteoarthritis (OA) and intercondylar notch narrowing based on
the notch width index. Methods Magnetic resonance (MR) images were collected from middle-aged and elderly patients with
a definite diagnosis of knee OA, including 42 with mild OA and 37 with moderate to severe OA, with 70 healthy individuals
serving as the control group. The notch width indexes NWI, NWI-A, and NWI-P on the coronal images at different levels were
calculated, and the intercondylar notch was classified, according to the features on axial MR images, into types A, U, and W.
The association of OA with NWI, NWI-A, NWI-P, and notch type was determined, and the cutoff values were obtained based
on the ROC curves at different levels as indicators for diagnosis of intercondylar notch stenosis. Results In the control, mild
OA, moderate to severe OA groups, the NWI value on coronal MR images were 0.252±0.019, 0.251±0.017, and 0.240±0.020,
NWI-A were 0.261±0.024, 0.259±0.023, and 0.245±0.023, and NWI-P were 0.271±0.026, 0.270±0.024, and 0.254±0.022, respectively.
Patients with moderate to severe OA had significantly smaller NWI, NWI-A, and NWI-P than the other two groups (P<0.05),
and a significant association was found between NWI values at each level and the occurrence of moderate to severe OA (P<
0.01). A NWI value<0.248, NWI-A<0.256, and NWI-P<0.266 supported a diagnosis of intercondylar notch narrowing. Type A
intercondylar notch was found in the majority of patients with intercondylar notch narrowing (P<0.05). Conclusion Patients
with moderate to severe OA have significant intercondylar notch narrowing, and patients with a type A intercondylar notch
are more likely to have intercondylar notch narrowing than those with type U notch.