The aim of this study is to investigate the relationship between knee joint angles, IFP stiffness, in OA patients using ultrasound elastography. The aim of this study is to investigate the relationship between knee joint angles, IFP stiffness, in OA patients using ultrasound elastography.
Sixteen patients with knee OA (mean age 76.0) and 14 healthy elderly controls (mean age 76.2) participated. IFP stiffness was measured in the supine position at maximum knee extension, 45°, 90°, and maximum flexion using ultrasound elastography (Aplio i-700, Canon Medical Systems). Stiffness was measured in the superficial layer of the IFP, located beneath the patellar tendon, using a 5mm circle region of interest to calculate mean shear wave speed. Stiffness was determined from the propagation speed. The maximum extension and flexion angles were measured using a goniometer. For knee OA patients, knee pain intensity was measured using Numeric Rating Scale (NRS). A two-way repeated measures ANOVA was used to analyze the effects of group and joint angle on IFP stiffness, with Bonferroni’s method applied for post-hoc comparisons. Spearman’s correlation was used to test the relationship between IFP stiffness and knee function.
In knee OA, there were 2 individuals classified as Kellgren-Lawrence grade II, 7 in grade III, and 7 in grade IV, with knee pain intensity of 4.18 ± 1.65 on the NRS. IFP stiffness in OA patients at maximum extension, 45°, 90°, and maximum flexion was 2.19 ± 0.58, 2.41 ± 0.76, 2.45 ± 0.91, and 3.24 ± 0.98 kPa, respectively, compared to 1.63 ± 0.56, 2.02 ± 0.51, 2.36 ± 0.84, and 1.89 ± 1.00 kPa in controls. ANOVA showed a significant main effect for group (p 0.01) and joint angle (p = 0.01), as well as an interaction effect (p = 0.01). Knee OA showed significant higher stiffness at full extension (p=0.01) and full flexion (p0.01) than controls. Maximum extension and flexion angles were -4.1 ± 4.6 and 128.8 ± 17.3 degrees in knee OA patients and 0.0 ± 0.0 and 141.8 ± 8.9 degrees in controls. The IFP stiffness did not show any significant correlations with either range of motion or knee pain intensity.
IFP stiffness increases during knee flexion, particularly in OA patients, with the most significant rise at full flexion. Although this increase may relate to the limited IPF space within the knee joint, no clear relationship with knee pain or range of motion was established.
The increase in IFP stiffness during knee flexion indicates that elevated pressure in this position may be a key factor in knee OA pathology.
knee osteoarthritis
elastography
