Background: Patellar height has been related to anterior knee pain and Osgood–Schlatter disease. To study the influence of patellar height on knee biomechanics, a bidimensional photoelastic prototype of the patellofemoral joint was developed. Methods: Nine tests were performed at different knee flexion angles and patellar heights. A free body diagram was constructed for each test. The following parameters were calculated: lengths (patella, patella thickness and ligamentum patellae); patellar height index; angles (knee flexion, patellar flexion, quadriceps and ligamentum patellae force and reaction force at the ankle); moment arms (extensor, quadriceps and ligamentum patellae in relation to both the tibiofemoral and patellofemoral contact points), effective moment arm and forces around the extensor mechanism relative to the applied force. Results: Femoropatellar and femorotibial reaction forces were greater with increased knee flexion and a fixed patellar height. With fixed knee flexion and different patellar heights, these forces were greater if the patella was elevated. A decrease in the angle between the tibial axis and ligamentum patellae was observed when patellar height increased. Patellar flexion angle increased when patellar height increased. This was accompanied by an increase in the angle of action of the quadriceps force. Extensor moment arm decreased with increased patellar height when knee flexion and the tibiofemoral contact point were fixed. Conclusion: A new application of photoelasticity is presented. The preliminary findings obtained confirm the influence of patellar height on patellar biomechanics, and specifically on forces around the extensor mechanism of the knee.

中文翻译：

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研究髌骨高度的髌股关节光弹模型

背景：髌骨高度与膝前疼痛和 Osgood-Schlatter 病有关。为研究髌骨高度对膝关节生物力学的影响，研制了髌股关节二维光弹性原型。方法：在不同的膝关节屈曲角度和髌骨高度进行了九次测试。为每个测试构建了一个自由体图。计算了以下参数：长度（髌骨、髌骨厚度和髌韧带）；髌骨高度指数；角度（膝关节屈曲、髌骨屈曲、股四头肌和髌韧带力以及踝关节的反作用力）；力臂（伸肌、股四头肌和髌韧带相对于胫股和髌股关节接触点）、有效力臂和伸肌机构周围相对于施加力的力。结果：随着膝关节屈曲度的增加和固定的髌骨高度，股髌骨和股胫骨的反作用力更大。在固定膝关节屈曲和不同髌骨高度的情况下，如果髌骨抬高，这些力会更大。当髌骨高度增加时，观察到胫骨轴和髌韧带之间的角度减小。髌骨高度增加时，髌骨屈曲角度增加。这伴随着股四头肌力量作用角度的增加。当膝关节屈曲和胫股接触点固定时，伸肌力臂随着髌骨高度的增加而减小。结论：提出了一种新的光弹性应用。获得的初步研究结果证实了髌骨高度对髌骨生物力学的影响，特别是对膝关节伸肌机制周围的力的影响。