PURPOSE To investigate the in vivo femoral condyle motion and synergistic function of the ACL/PCL along the weight-bearing knee flexion. METHODS Twenty-two healthy human knees were imaged using a combined MRI and dual fluoroscopic imaging technique during a single-legged lunge (0°-120°). The medial and lateral femoral condyle translation and rotation (measured using geometric center axis-GCA), and the length changes of the ACL/PCL were analyzed at: low (0°-30°), mid-range (30°-90°) and high (90°-120°) flexion of the knee. RESULTS At low flexion (0°-30°), the strains of the ACL and the posterior-medial bundle of the PCL decreased. The medial condyle showed anterior translation and lateral condyle posterior translation, accompanied with a sharp increase in external GCA rotation (internal tibial rotation). As the knee continued flexion in mid-range (30°-90°), both ACL and PCL were slack (with negative strain values). The medial condyle moved anteriorly before 60° of flexion and then posteriorly, accompanied with a slow increase of GCA rotation. As the knee flexed in high flexion (90°-120°), only the PCL had increasingly strains. Both medial and lateral condyles moved posteriorly with a rather constant GCA rotation. CONCLUSIONS The ACL and PCL were shown to play a reciprocal and synergistic role during knee flexion. Mid-range reciprocal anterior-posterior femoral translation or laxity corresponds to minimal constraints of the ACL and PCL, and may represent a natural motion character of normal knees. The data could be used as a valuable reference when managing the mid-range "instability" and enhancing high flexion capability of the knee after TKAs. LEVEL OF EVIDENCE Level IV.

中文翻译：

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负重屈曲过程中膝关节的体内运动学和韧带功能：膝关节中位屈曲的研究。

目的研究ACL / PCL沿负重膝关节屈曲的体内股骨con运动和协同功能。方法在单腿弓形（0°-120°）期间，使用MRI和双透视成像技术，对22个健康的人类膝盖进行了成像。股骨内侧和外侧lateral的平移和旋转（使用几何中心轴-GCA测量）以及ACL / PCL的长度变化在以下条件下进行分析：低（0°-30°），中距离（30°-90° ）和膝盖的高屈曲（90°-120°）。结果在低屈曲度（0°-30°）下，ACL的张力和PCL的后内侧束减少。内侧con表现为前移和外侧后移，并伴有外部GCA旋转（胫骨内部旋转）的急剧增加。当膝盖在中间范围（30°-90°）内持续弯曲时，ACL和PCL均松弛（负应变值）。内侧con在屈曲60°之前先向后移动，然后向后移动，同时GCA旋转缓慢增加。当膝盖以高屈曲度（90°-120°）屈曲时，只有PCL的压力越来越大。内侧和外侧con均向后移动，同时GCA旋转相当恒定。结论ACL和PCL在膝关节屈曲过程中起着相互促进的作用。中等范围的前后股骨平移或松弛对应于ACL和PCL的最小约束，并且可能代表正常膝盖的自然运动特征。在管理中档“不稳定性”时，该数据可以用作有价值的参考 并提高了膝关节置换术后膝关节的高屈曲能力。证据级别IV。