Knee dislocation
A knee dislocation is an injury in which there is disruption of the knee joint between the tibia and the femur. Symptoms include pain and instability of the knee. Complications may include injury to an artery, most commonly the popliteal artery behind the knee, or compartment syndrome. About half of cases are the result of major trauma and about half as a result of minor trauma. About 50% of the time, the joint spontaneously reduces before arrival at hospital. Typically there is a tear of the anterior cruciate ligament, posterior cruciate ligament, and either the medial collateral ligament or lateral collateral ligament. If the ankle–brachial pressure index is less than 0.9, CT angiography is recommended to detect blood vessel injury. Otherwise repeated physical exams may be sufficient. More recently, the FAST-D protocol, assessing the posterior tibial and dorsalis pedis arteries for a ‘tri-phasic wave pattern’ with ultrasound, has been shown to be reliable in ruling out significant arterial injury. If the joint remains dislocated, reduction and splinting is indicated; this is typically carried out under procedural sedation. If signs of arterial injury are present, immediate surgery is generally recommended. Multiple surgeries may be required. In just over 10% of cases,