Infrapatellar Fat Pad Stiffness Linked to Severe Knee Osteoarthritis Symptoms: Study
A new study published in Clinical Rheumatology has found that higher stiffness of the infrapatellar fat pad (IFP) is highly correlated with more extreme knee osteoarthritis (OA) symptoms, indicating that IFP stiffness may be a key marker to determine knee OA severity. The correlation was detected in a study that investigated the correlation between IFP stiffness and thickness with knee OA severity and knee symptoms. The study was conducted by Sayaka O. and colleagues.
Knee osteoarthritis is a degenerative joint disease with joint pain, stiffness, and decreased mobility. The infrapatellar fat pad, under the kneecap, is a soft tissue structure that can be structurally modified by inflammation and mechanical loading. Elucidation of the function of IFP in knee OA may enhance diagnostic and therapeutic approaches.
The present study involved 93 subjects, divided into three groups according to knee OA severity:
• Control Group: 27 subjects with asymptomatic knees and Kellgren–Lawrence (KL) grade 0 or 1.
• Mild OA Group: 22 subjects with symptomatic medial knee OA (KL grade 2).
• Severe OA Group: 44 subjects with severe knee OA (KL grades 3 and 4).
Assessment Tools:
• IFP Stiffness (Shear Modulus): Quantified by ultrasonography, yielding a measure of tissue rigidity.
• IFP Thickness: Quantified by ultrasonography.
• Knee Society Score (KSS): Utilized to assess knee symptoms, such as pain and functional restriction.
• Maximum Knee Extension Strength and External Knee Adduction Moment: Assessed during walking to determine functional capability.
Data Analysis:
• The thickness and shear modulus of the IFP were compared between the three groups.
• Multiple regression analysis was employed to determine the relationship between IFP properties and symptoms of the knee (KSS scores).
Key Findings
• IFP Stiffness and Knee OA SeverityIFP shear modulus (stiffness) was much greater in the severe OA group than in the control group.
• There were no significant differences in IFP stiffness between the mild OA group and the control group.
• No significant differences were found in IFP thickness between the three groups.
Association with Knee Symptoms:
• Greater IFP stiffness was significantly correlated with more severe knee symptoms, reflected by lower KSS scores.
• Conversely, IFP thickness had no correlation with knee symptoms, meaning that size does not determine symptom severity.
This study demonstrated that stiffness of infrapatellar fat pad, rather than thickness, is strongly associated with knee osteoarthritis symptom severity and symptoms. These findings suggest that IFP stiffness can potentially be both a diagnostic tool and a potential therapeutic target in the treatment of knee OA, providing a new option to improve patient outcomes.
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