page_title: Knee dislocation
section_title: Diagnosis
hierarchical_section_title: Knee dislocation / Diagnosis
caption_attribution_description: English: The circled area denotes an avulsion fracture fragment (aka. Segond fracture) of 16 year old who tore his anterior cruciate ligament (ACL) and medial meniscus during an athletic event. MRI confirmed the 16 year-old's injury.
context_page_description: A knee dislocation is a knee injury in which there is a complete disruption of the joint between the tibia and the femur. Symptoms include knee pain and instability of the knee. Complications may include injury to an artery around the knee, most commonly the artery behind the knee, or compartment syndrome.
  About half of cases are the result of major trauma and about half occur as a result of minor trauma. In about half of cases the joint reduces itself before a person arrives at the hospital. Typically there is a break 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.
  If the joint remains dislocated, reduction and splinting is indicated; this is typically carried out under procedural sedation. In those with signs of arterial injury, immediate surgery is generally carried out. Multiple surgeries may be required. In just over 10% of cases, an amputation of part of the leg is required.
context_section_description: As the injury may reduce on its own before a person arrives at the hospital, the diagnosis may be missed. Diagnosis may be suspected based on the history of the injury and a physical examination. This may include anterior drawer test, valgus stress test, varus stress test, and posterior sag test. An accurate physical exam can be difficult due to pain.
  Plain X-rays, CT scan, ultrasonography, or MRI may help with the diagnosis. Findings on X-ray that may be useful among those who have already reduced include a variable joint space, subluxation of the joint, or a Segond fracture.
  If the ankle–brachial pressure index (ABI) is less than 0.9, CT angiography is recommended. Standard angiography may also be used. If the ABI is greater than 0.9 repeated physical exams over the next 24 hours to verify good blood flow may be sufficient. The ABI is calculated by taking the systolic blood pressure at the ankle and dividing it by the systolic blood pressure in the arm.
caption: A Segond fracture seen on X-ray
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