Knee dislocation

Source: Wikipedia, the free encyclopedia.
Not to be confused with Patellar dislocation.

Knee dislocation
ACL tear[6]
TreatmentReduction, splinting, surgery[4]
Prognosis10% risk of amputation[4]
Frequency1 per 100,000 per year[3]

A knee dislocation is an

injury to an artery, most commonly the popliteal artery behind the knee, or compartment syndrome.[3][4][7]

About half of cases are the result of

physical exams may be sufficient.[2] 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.[8]

If the joint remains dislocated,

procedural sedation.[2] If signs of arterial injury are present, immediate surgery is generally recommended.[3] Multiple surgeries may be required.[4] In just over 10% of cases, an amputation of part of the leg is required.[4]

Knee dislocations are rare, occurring in about 1 per 100,000 people per year.[3] Males are more often affected than females.[2] Younger adults are most often affected.[2] Descriptions of this injury date back to at least 20 BC by Meges of Sidon.[9]

Signs and symptoms

CT angiogram 3D reconstruction, posterior view showing a normal artery on the left, and occlusion to right popliteal artery as a result of a knee dislocation[10]

Symptoms include knee pain.[2] The joint may also have lost its normal shape and contour.[2] A joint effusion may, or may not, be present.[2]

Complications

Complications may include injury to the

common peroneal nerve or tibial nerve may also occur.[2] Nerve problems, if they occur, often persist to a variable degree.[11]

Cause

About half are the result of

motor vehicle collisions, or a pedestrian being hit by a motor vehicle.[2] Cases due to major trauma often have other injuries.[5]

Minor trauma may include tripping while walking or while playing sports.[2] Risk factors include obesity.[2]

The condition may also occur in a number of genetic disorders such as

Ellis–van Creveld syndrome, Larsen syndrome, and Ehlers–Danlos syndrome.[12]

Diagnosis

A Segond fracture seen on X-ray

As the injury may have self-reduced before arrival at hospital, the diagnosis may not be readily apparent.

posterior sag test.[5] An accurate physical exam can be difficult due to pain.[5]

Plain X-rays, CT scan,

MRI may help with the diagnosis.[2][11] 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.[5]

If the

systolic blood pressure at the ankle and dividing it by the systolic blood pressure in the arm.[2] More recently, the FAST-D protocol, using ultrasound to assess the posterior tibial and dorsalis pedis arteries for a ‘tri-phasic wave pattern’, has been shown to be reliable in ruling out significant arterial injury.[8]

Classification

A lateral dislocation of the knee

They may be divided into five types: anterior, posterior, lateral, medial, and rotatory.[4] This classification is based on the movement of the tibia with respect to the femur.[11] Anterior dislocations, followed by posterior, are the most common.[2] They may also be classified on the basis of which ligaments are injured.[2]

Treatment

Initial management is often based on

procedural sedation.[11] If the joint cannot be reduced in the emergency department, then emergency surgery is recommended.[2]

In those with signs of arterial injury, immediate surgery is generally carried out.[3] If the joint does not stay reduced external fixation may be needed.[2] If the nerves and artery are intact the ligaments may be repaired after a few days.[11] Multiple surgeries may be required.[4] In just over 10% of cases an amputation of part of the leg is required.[4]

Epidemiology

Knee dislocations are rare: they represent about 1 in 5,000 orthopedic injuries,[5] and about 1 knee dislocation occurs annually per 100,000 people.[3] Males are more often affected than females, and young adults the most often.[2]

References

  1. PMID 20411095
    .
  2. ^
    S2CID 10713473
    .
  3. ^
    S2CID 3482099
    .
  4. ^
    ISBN 978-1-4377-1503-3
    .
  5. ^
    PMID 26410637
    .
  6. ISBN 978-1455725021
    .
  7. PMID 24554457
    .
  8. ^
    PMID 28324353
    .
  9. ISBN 9781449985219
    .
  10. PMID 28246569
    .
  11. ^
    ISBN 978-0-323-35479-0
    .
  12. ISBN 978-0-323-29494-2
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=Knee_dislocation&oldid=1188217167"