1. Signs and symptoms
    Complications 

2. Cause

3. Diagnosis
    Classification 

4. Treatment

5. Epidemiology

6. References

A knee dislocation is a knee injury in which there is a complete disruption of the joint between the tibia and the femur.^[3][3] Symptoms include knee pain and instability of the knee.^[4] Complications may include injury to an artery around the knee, most commonly the artery behind the knee, or compartment syndrome.^[3][3][5]

About half of cases are the result of major trauma and about half occur as a result of minor trauma.^[3] In about half of cases the joint reduces itself before a person arrives at the hospital.^[3] Typically there is a break of the anterior cruciate ligament, posterior cruciate ligament, and either the medial collateral ligament or lateral collateral ligament.^[3] If the ankle–brachial pressure index is less than 0.9, CT angiography is recommended to detect blood vessel injury.^[3] Otherwise repeated physical exams may be sufficient.^[4]

If the joint remains dislocated, reduction and splinting is indicated;^[3] this is typically carried out under procedural sedation.^[4] In those with signs of arterial injury, immediate surgery is generally carried out.^[3] Multiple surgeries may be required.^[3] In just over 10% of cases, an amputation of part of the leg is required.^[3]

Knee dislocations are rare, occurring in about 1 per 100,000 people per year.^[6] Males are more often affected than females.^[4] Younger adults are most often affected.^[4] Descriptions of this injury date back to at least 20 BC by Meges of Sidon.^[7]

Signs and symptoms

Symptoms include knee pain.^[4] The joint may also be obviously out of place.^[4] A joint effusion is not always present.^[4]

Complications

Complications may include injury to the artery behind the knee in about 20% of cases or compartment syndrome.^[6][3] Damage to the common peroneal nerve or tibial nerve may also occur.^[4] Nerve problems if they occur often never fully heal.^[40]

Cause

About half are the result of major trauma and about half occur as a result of minor trauma.^[6] Major trauma may include mechanisms like falls from a significant height, motor vehicle collisions, or a pedestrian being hit by a motor vehicle.^[4] Cases due to major trauma often have other injuries.^[9]

Minor trauma may include tripping while walking or while playing sports.^[4] Risk factors include obesity.^[4]

The condition may also occur in a number of genetic disorders such as Ellis–van Creveld syndrome, Larsen syndrome, and Ehlers–Danlos syndrome.^[10]

Diagnosis

As the injury may reduce on its own before a person arrives at the hospital, the diagnosis may be missed.^[4] Diagnosis may be suspected based on the history of the injury and a physical examination.^[9] This may include anterior drawer test, valgus stress test, varus stress test, and posterior sag test.^[9] An accurate physical exam can be difficult due to pain.^[9]

Plain X-rays, CT scan, ultrasonography, or MRI may help with the diagnosis.^[4][40] 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.^[9]

If the ankle–brachial pressure index (ABI) is less than 0.9, CT angiography is recommended.^[6] Standard angiography may also be used.^[4] If the ABI is greater than 0.9 repeated physical exams over the next 24 hours to verify good blood flow may be sufficient.^[4][40] The ABI is calculated by taking the systolic blood pressure at the ankle and dividing it by the systolic blood pressure in the arm.^[4]

Classification

They may be divided into five types: anterior, posterior, lateral, medial, and rotatory.^[3] This classification is based on the movement of the tibia with respect to the femur.^[11] Anterior dislocations are the most common, followed by posterior dislocations.^[4] They may also be classified based on what ligaments are damaged.^[4]

Treatment

Initial management is often based on Advanced Trauma Life Support.^[9] If the joint remains dislocated reduction and splinting is indicated.^[3] Reduction can often be done with simple traction after the person has received procedural sedation.^[11] If the joint cannot be reduced in the emergency department emergency surgery is recommended.^[4]

In those with signs of arterial injury immediate surgery is generally carried out.^[6] If the joint does not stay reduced external fixation may be needed.^[4] If the nerves and artery are intact the ligaments may be repaired after a few days.^[11] Multiple surgeries may be required.^[3] In just over 10% of cases an amputation of part of the leg is required.^[3]

Epidemiology

Knee dislocations are rare: they represent about 1 in 5,000 orthopedic injuries,^[9] and about 1 knee dislocation occurs annually per 100,000 people.^[6] Males are more often affected than females, and young adults are most often affected.^[4]

References

• Bodmin Borough Police
• Bodmin by-election, 1906
• Bodmin by-election, 1916
• Bodmin by-election, 1922
• Bodmin by-election, 1941
• Bodmin Parish Church
• Bodmin Town Council
• Bodnant viburnum
• Bodnar, Andrew
• Bodnarchuk, Andrew
• Bodney v Bennell
• Bodo Accord
• Bodo Andreass
• Bodo Baptist Convention
• Bodo (bishop)
• Bodoc
• Bodo, Cameroon
• Bodoc (disambiguation)
• Bodo (Central African Republic)
• Bodo, Chad
• Bodo Cranium
• Bodo (Didiévi)
• Bodo (Excavata)
• Bodo films
• Bodog