Knee dislocations can be further divided into high-velocity and low-velocity categories. 7, 19–21 Although the mechanism varies for each classification of knee dislocation, most involve significant forces delivered in a violent manner to the knee. 3, 7, 10, 12, 13 Posterolateral dislocations are considered to be very difficult, if not impossible, to reduce by closed methods. 2–4, 7, 17, 18 Rotary dislocations can further be divided into anteromedial, anterolateral, posteromedial, and posterolateral injuries. 2, 3, 12, 13 Knee dislocations occur in 5 main types: anterior, posterior, medial, lateral, and rotary. Knee dislocations are typically classified in terms of tibial displacement with respect to the femur. The peroneal nerve passes around the proximal fibula just distal to the fibular head. 1, 2, 10, 14, 16 The tibial nerve joins the popliteal artery in the popliteal fossa but is not tethered to the knee. 2 Despite the apparent abundance of collateral blood supply, these genicular arteries cannot compensate for a ruptured popliteal artery. 14, 15 Also supplying collateral circulation to the knee are the lateral femoral circumflex and anterior tibial arteries. 1, 2, 7, 10 Inside the popliteal fossa, the popliteal artery gives off 5 genicular arteries 1, 2, 4, 12: paired superior and paired inferior arteries and the middle genicular artery. The popliteal artery attaches proximally to the adductor hiatus and distally to the fibrous arch of the soleus muscle. 2 The muscles and tendons that aid in stabilizing the knee include the vastus lateralis, vastus medialis, vastus intermedius, rectus femoris, biceps femoris, semitendinosus, semimembranosus, sartorius, gracilis, iliotibial tract, popliteus, and gastrocnemius. 2, 13 The medial and lateral menisci transmit axial loads and stabilize against any rotational forces. 2, 10–12 Excessive valgus forces are restrained by the medial collateral ligament (MCL), whereas excessive varus forces are restrained by the lateral collateral ligament (LCL). Anterior and posterior tibial translations are prevented by the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), respectively. The knee complex is stabilized by 6 main ligamentous or cartilaginous structures as well as several muscles and tendons.
0 Comments
Leave a Reply. |