Besier Thor F, Pal Saikat, Draper Christine E, Fredericson Michael, Gold Garry E, Delp Scott L, Beaupré Gary S
1Auckland Bioengineering Institute, University of Auckland, Auckland, NEW ZEALAND; 2Department of Engineering Science, University of Auckland, Auckland, NEW ZEALAND; 3College of Engineering, California Polytechnic State University, San Luis Obispo, CA; 4Department of Bioengineering, Stanford University, Stanford, CA; 5Department of Orthopaedics, Stanford University, Stanford, CA; 6Department of Radiology, Stanford University, Stanford, CA; and 7VA Palo Alto Rehabilitation Research and Development Center, Palo Alto, CA.
Med Sci Sports Exerc. 2015 Nov;47(11):2416-22. doi: 10.1249/MSS.0000000000000685.
Elevated cartilage stress has been identified as a potential mechanism for retropatellar pain; however, there are limited data in the literature to support this mechanism. Females are more likely to develop patellofemoral pain than males, yet the causes of this dimorphism are unclear. We used experimental data and computational modeling to determine whether patients with patellofemoral pain had elevated cartilage stress compared with pain-free controls and test the hypothesis that females exhibit greater cartilage stress than males.
We created finite element models of 24 patients with patellofemoral pain (11 males and 13 females) and 16 pain-free controls (8 males and 8 females) to estimate peak patellar cartilage stress (strain energy density) during a stair climb activity. Simulations took into account cartilage morphology from magnetic resonance imaging, joint posture from weight-bearing magnetic resonance imaging, and muscle forces from an EMG-driven model.
We found no difference in peak patellar strain energy density between those with patellofemoral pain (1.9 ± 1.23 J·m(-3)) and control subjects (1.66 ± 0.75 J·m(-3), P = 0.52). Females exhibited greater cartilage stress compared with males (2.2 vs 1.3 J·m(-3), respectively; P = 0.0075), with large quadriceps muscle forces (3.7 body weight in females vs 3.3 body weight in males) and 23% smaller joint contact area (females, 467 ± 59 mm2, vs males, 608 ± 95 mm2).
Patients with patellofemoral pain did not display significantly greater patellar cartilage stress compared with pain-free controls; however, there was a great deal of subject variation. Females exhibited greater peak cartilage stress compared with males, which might explain the greater prevalence of patellofemoral pain in females compared with that in males, but other mechanical and biological factors are clearly involved in this complex pathway to pain.
髌股关节软骨应力升高已被确定为髌后疼痛的一种潜在机制；然而，文献中支持这一机制的数据有限。女性比男性更易患髌股关节疼痛，但其性别差异的原因尚不清楚。我们使用实验数据和计算模型来确定与无疼痛对照组相比，髌股关节疼痛患者的软骨应力是否升高，并检验女性比男性表现出更大软骨应力的假设。
我们创建了24例髌股关节疼痛患者（11例男性和13例女性）和16例无疼痛对照组（8例男性和8例女性）的有限元模型，以估计上楼梯活动过程中髌软骨的峰值应力（应变能密度）。模拟考虑了磁共振成像的软骨形态、负重磁共振成像的关节姿势以及肌电图驱动模型的肌肉力量。
我们发现髌股关节疼痛患者（1.9±1.23J·m⁻³）和对照组（1.66±0.75J·m⁻³，P = 0.52）之间的髌峰值应变能密度无差异。与男性相比，女性表现出更大的软骨应力（分别为2.2与1.3J·m⁻³；P = 0.0075），股四头肌力量较大（女性为3.7倍体重，男性为3.3倍体重），关节接触面积小23%（女性为467±59mm²，男性为608±95mm²）。
与无疼痛对照组相比，髌股关节疼痛患者的髌软骨应力并未显著增加；然而，个体差异很大。与男性相比，女性表现出更大的软骨峰值应力，这可能解释了女性髌股关节疼痛的患病率高于男性，但其他机械和生物学因素显然也参与了这一复杂的疼痛途径。
