Pettenuzzo Sofia, Berardo Alice, Belluzzi Elisa, Pozzuoli Assunta, Ruggieri Pietro, Carniel Emanuele Luigi, Fontanella Chiara Giulia
Department of Civil, Environmental and Architectural Engineering (DICEA), University of Padova, Padova, Italy.
Centre for Mechanics of Biological Materials, University of Padova, Padova, Italy.
Connect Tissue Res. 2025 Jul;66(4):272-283. doi: 10.1080/03008207.2025.2502591. Epub 2025 May 9.
Osteoarthritis (OA) is the most common musculoskeletal disorder, primarily affecting knee joints and causing pain and disability. The infrapatellar (IFP) and the suprapatellar (SFP) fat pad are knee adipose tissues that play essential mechanical roles during articular activity but are also sources of adipokines and cytokines, contributing to OA progression. For this reason, this work aims to provide new insights into IFP and SFP implications in knee OA.
IFP and SFP tissue mechanical properties were studied through compression, indentation and shear mechanical tests performed on samples collected from patients who underwent total knee arthroplasty surgery due to end-stage OA. The energy loss, peak stress, and initial and final elastic moduli were calculated from the unconfined compression tests. The time-dependent response, evaluated in terms of equilibrium relative stiffness, was computed from stress-relaxation loading conditions. Considering shear tests, they provided strain-energy dissipation density, peak shear stress, and the shear moduli.
Experimental results showed the typical adipose tissue mechanics features: non-linear stiffening with strain and time-dependent response. Experimental results showed that OA IFP is stiffer than OA SFP, indeed IFP final compression elastic modulus was greater than the SFP (84.43 kPa vs 35.54 kPa respectively) ( = 0.042). Regarding the viscoelastic properties they were comparable: the equilibrium relative stiffness was reported as 0.13 for IFP and 0.11 for SFP ( = 0.026).
These outcomes provide new insights into the OA influence on knee mechanics and lay the basis for developing computational tools to improve knee prosthesis design.
骨关节炎（OA）是最常见的肌肉骨骼疾病，主要影响膝关节，导致疼痛和残疾。髌下（IFP）和髌上（SFP）脂肪垫是膝关节脂肪组织，在关节活动中起重要的力学作用，但也是脂肪因子和细胞因子的来源，促进OA进展。因此，本研究旨在深入了解IFP和SFP在膝关节OA中的作用。
通过对因终末期OA接受全膝关节置换手术患者采集的样本进行压缩、压痕和剪切力学测试，研究IFP和SFP组织的力学性能。从无侧限压缩试验中计算能量损失、峰值应力以及初始和最终弹性模量。根据应力松弛加载条件计算以平衡相对刚度表示的时间依赖性响应。对于剪切试验，计算应变能耗散密度、峰值剪切应力和剪切模量。
实验结果显示了典型的脂肪组织力学特征：随应变和时间依赖性响应的非线性硬化。实验结果表明，OA的IFP比OA的SFP更硬，实际上IFP的最终压缩弹性模量大于SFP（分别为84.43 kPa和35.54 kPa）（P = 0.042）。关于粘弹性特性，两者相当：IFP的平衡相对刚度为0.13，SFP为0.11（P = 0.026）。
这些结果为OA对膝关节力学的影响提供了新的见解，并为开发改进膝关节假体设计的计算工具奠定了基础。
