Levitt Sarah J, Zazulak Bohdanna, Green Joshua S, Medvecky Michael J
Frank H. Netter MD School of Medicine, Quinnipiac University, North Haven, Connecticut, USA.
Department of Orthopedics & Rehabilitation, Yale School of Medicine, New Haven, Connecticut, USA.
Video J Sports Med. 2024 Aug 13;4(4):26350254241241082. doi: 10.1177/26350254241241082. eCollection 2024 Jul-Aug.
The posterolateral corner (PLC) of the knee comprises important static and dynamic stabilizers, including the lateral collateral ligament, popliteus tendon, biceps femoris tendon, the popliteofibular ligament, and the posterolateral capsule. These structures are disrupted in many knee injuries, yet may be overlooked due to the complex anatomy, subjective clinical diagnostic exams, and poorly defined imaging techniques. Complete PLC lesions rarely heal with non-operative treatment, and can lead to significant instability and poor outcomes, and are therefore most successfully treated surgically.
A thorough physical examination and a high index of suspicion is necessary when evaluating the knee to identify these occult injuries. Current physical exam testing for PLC injuries typically includes side to side comparisons of the varus stress test, dial test, and heel-to-table distance. However, these injuries continue to be under-diagnosed as global clinical consensus for PLC injury identification remains elusive.
In these videos, we show the "active external rotation sign" where chronic posterior cruciate ligament-PLC deficient patients are positioned in 90° of knee flexion and are instructed to actively contract their hamstrings. Verbal cues given to the patient include "contract your hamstrings" and "dig the back of your heel into the ground." This can result in dynamic external rotation of the tibia with simultaneous posterior tibial translation on the femur. The biceps femoris pulls on the fibula and without the PLC to stabilize the knee, tibiofibular external rotation and posterior translation occurs. The biomechanics are similar to the dial test, but this detection tool utilizes active motion instead of passive motion, and presents with this abnormal and asymmetric knee motion.
The purpose of this presentation is to describe and demonstrate an important clinical sign that may be seen with chronic PLC injuries and that may be used as a new test for diagnosis.
DISCUSSION/CONCLUSION: Detection of PLC injuries with the active external rotation sign may assist in the clinical detection of incompetent PLC function, which can put cruciate reconstruction surgery at risk of failure if not simultaneously addressed.
The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.
膝关节后外侧角（PLC）包含重要的静态和动态稳定结构，包括外侧副韧带、腘肌腱、股二头肌腱、腘腓韧带和后外侧关节囊。这些结构在许多膝关节损伤中会受到破坏，但由于解剖结构复杂、临床诊断检查主观性强以及成像技术定义不明确，可能会被忽视。完全性PLC损伤很少能通过非手术治疗愈合，会导致明显的不稳定和不良后果，因此手术治疗最为成功。
在评估膝关节以识别这些隐匿性损伤时，进行全面的体格检查并保持高度怀疑是必要的。目前针对PLC损伤的体格检查通常包括内翻应力试验、旋转试验和足跟至台面距离的左右对比。然而，这些损伤仍然诊断不足，因为关于PLC损伤识别的全球临床共识仍难以达成。
在这些视频中，我们展示了“主动外旋征”，即慢性后交叉韧带 - PLC 损伤患者处于膝关节屈曲90°位，被指示主动收缩其腘绳肌。给患者的言语提示包括“收缩你的腘绳肌”和“将脚跟后部压向地面”。这会导致胫骨动态外旋，同时胫骨在股骨上向后移位。股二头肌牵拉腓骨，由于没有PLC稳定膝关节，会发生胫腓骨外旋和后移。其生物力学与旋转试验相似，但这种检测工具利用主动运动而非被动运动，并表现出这种异常和不对称的膝关节运动。
本报告的目的是描述和展示一种可能在慢性PLC损伤中出现的重要临床体征，并可将其用作新的诊断测试。
讨论/结论：通过主动外旋征检测PLC损伤可能有助于临床检测PLC功能不全，如果不同时解决，这可能会使交叉韧带重建手术面临失败风险。
作者证明已获得本出版物中出现的任何患者的同意。如果个体可识别，作者已随本提交的出版物包含患者的豁免声明或其他书面批准形式。
