Cutting edge Orthopedics

Knee Dislocations • 37  Interpretation of Clinical Presentation The patient presents with a clinical picture consistent with a knee dislocation. The mechanism of injury involves a motorcycle accident, which suggests a high energy. He complains of right leg pain, but no deformity is noted on initial survey. On exam, he has laxity to anterior and posterior drawer, as well as varus and valgus stress. This suggests that he has likely injured both cruciate lig- aments as well as both collaterals. In 1996, O’Shea and colleagues studied the reliability of physical exam findings in making the diagnosis of acute knee injuries [1]. They prospectively made a diag- nosis on 156 knee injuries based only on history, physical exam findings, and plain radiographs. These diagnoses were compared with intraoperative findings to determine reliability. Their series included 67 ACL injuries and four PCL injuries. They diagnosed ACL injuries with 97% sensitivity and 100% specificity. PCL injuries in their series were diagnosed with 100% sensitivity and 99% specificity. However, when injuries were complicated by a second ipsilateral knee injury, such as an additional ligamentous or meniscal injuries, their diagnostic accuracy declined to 54%. Figure 1a, b is an AP and lateral of the right knee. No fractures are observed, but the knee has an effusion, radiographically. On the AP, the tibia is subluxated laterally and in varus, indicating ligamentous injury. This is further verified by the coronal MRI image seen in Fig. 2a–d, which demonstrates an avulsion of the medial collateral ligament off of the femur as well as a mid- substance tear of the lateral collateral ligament structures. The use of MRI has greatly improved the ability to diagnose knee dislocations, and the authors believe that the literature suggests that MRI is now the gold standard in diagnosis. In 1996, Twaddle and colleagues compared clinical findings to MRI in the ability to accurately diag- nose injuries in knee dislocations [2]. The investigators utilized intraoperative findings as the gold standard to compare these two methods. They found MRI to be 100% sensitive and 100% specific in diagnosing ACL, PCL, and patellar tendon injuries. Furthermore, when considering all liga- Fig. 1: ( a ) AP radiograph knee ( b ) Lateral radiograph knee. h energy. He complains of right leg deformity is noted on initial survey. verified by the coronal MRI image seen in Fig. 20.2a–d , which demonstrates an avulsion of ) AP ee ( b ) graph knee M. K. Yarlagadda et al.