Investigation of the biomechanical response of infrapatellar fat pad in osteoarthritic condition

The infrapatellar fat body (IFP) is situated between the patellar tendon, the femoral condyle and the tibial plateau of the knee. The IFP consists of adipose lobules delimited by connec-tive septa. The structural functionality of the IFP is debated and pertains to a cushioning role in the knee joint, providing to dis-tribute and to damp mechanical action during articular activity. In case of osteoarthritis (OA), IFP is found to be affected by in-flammation and fibrosis. The aim of the present study is to analyze the influence of the OA on the microscopic and the structural conformation with re-gard to mechanical properties. The microscopic analysis of the IFP was performed through histological and ultrastructural methods. The volume of IFP was segmented from Magnetic Res-onance images to identify the influence of OA. Geometrical data together with the constitutive tissue configuration of lobules and septa represent the basic data to provide numerical micro-models of the IFP. Numerical analyses were developed to evaluate the mechanical behavior considering the characteristic loading con-ditions as compression, torsion and shear actions. Results from histomorphometric investigations showed that the IFP affected by OA maintains similar lobules configuration but thicker interlobular septa. At the same time, the OA deter-mined a decrease in IFP volume. The results from numerical analysis pointed out the mechanical relevance of IFP and the loss of proper stress-strain performances of the OA IFP under me-chanical loads.