Dislocated Knee

What is a Knee Dislocation or Dislocated Knee?

An injury to the knee joint is a dislocation (this place is where two bones or more come together) and as a result the bones are forced out of their normal positions. Your knee joint will be immobilized and deformed temporarily due to knee dislocation or dislocated knee.

When the bones forming the knee are not in place, a knee dislocation or dislocated knee occurs. Ligaments are strong band of tissues holding the bones. The stabilization of a bone in a particular position is achieved through ligament. Tearing of the ligaments can cause knee dislocation or dislocated knee. Knee subluxation is the term given to partial dislocation of the knee joint. Disruption of the ligaments of patella (the knee cap) occurs in some injuries.

Knee Dislocation or Dislocated Knee

What is a Minor Knee Dislocation?

For the occurrence of a knee dislocation or dislocated knee, tearing of the knee joint ligaments must occur. Knee Subluxation is the term given to minor or partial dislocation of the knee.

What is the Difference Between Knee Dislocation/Dislocated Knee and Kneecap (Patellar) Dislocations?

Knee Dislocation/Dislocated Knee Vs. Patellar or Kneecap Dislocations

A substantial difference exists between patellar dislocation and knee dislocation or dislocated knee. Patellar dislocation is the most common.

Knee Dislocation or Dislocated Knee

A patellar dislocation/subluxation is different from a knee dislocation or dislocated knee. A medical emergency arises when a knee dislocates. When there is a major force or trauma, knee dislocation or dislocated knee will typically occur and this is whereby the boney structures and ligaments around/of the knee. Losing the leg can accrue with incorrect and delayed treatment. Severe pain will be felt due to deforming of the joint as a result of the knee dislocation.

Patellar or Kneecap Dislocations:

Patellar or Kneecap dislocation or subluxation occur due to patella moving out of the groove. It is more common for young athletes to regularly experience patellar subluxation. The knee's anatomical structure also determines the occurrence of most dislocations. Both noncontact and contact mechanism can cause it and it typically happens when a rapid change in direction or twisting occurs on the foot.

The straining ligaments are damaged severely due to a direct blow causing a dislocation. The tear is ruptured to the inability of the ligaments to dissipate. The symptoms from a dislocation of lateral patellar are: Acute swelling, pain that is extreme until occurrence of the relocation, continuous paining of the medial ligaments, medially discoloration of the ligament site, and inability to sense or apprehend the possibility of recurrence of another subluxation.

Classification of Knee Dislocation or Dislocated Knee

Basing on the direction of the tibia displacement, the knee dislocation or dislocated knee can be categorized as follows:

  1. Anterior Knee Dislocation or Dislocated Knee

    • This is the common type of dislocation (30-50%)
    • Results from hyperextension injury.
    • Tearing of PCL (posterior cruciate ligament) is involved.
    • Traction gives rise to the arterial injury which is an intimal tear in general.
  2. Posterior Knee Dislocation or Dislocated Knee

    • Second common type (25%)
    • Owing to a flexed knee to axial load (dashboard injury.)
    • The rate of tearing of popliteal artery is high.
  3. Lateral Knee Dislocation or Dislocated Knee

    • Dislocation of the knee is 13%
    • Owing to valgus or varus force.
    • ACL (anterior cruciate ligament) and PLC tears is usually involved
    • The rate of peroneal nerve injury is high
  4. Medial Knee Dislocation or Dislocated Knee

    • Valgus or varus force
    • PLC and ACL (anterior cruciate ligament) disruption
  5. Rotational Knee Dislocation or Dislocated Knee

    • Posterolateral rotational dislocation is most common.
    • Irreducible usually.

Wascher and Schenck Classification of Knee Dislocation or Dislocated Knee

Schenck developed anatomical classification procedure and Wascher modified it. The ligamentous/anatomical nature of the injury is used in its description.

      • KD I- Multiligamentous ruptures resulting with cruciate intact.
      • KD II- Bicruciate ruptures involving both collaterals intact though it's rare.
      • KD IIIM - Bicruciate and the rupture of the MCL (medial collateral ligament)
      • KD IIIL - Bicruciate and the rupture of LCL (lateral collateral ligament)
      • KD IV - Rupture of panligament
      • KD V- Periarticular fracture accompanying knee dislocation or dislocated knee
      • C (with addition of the above) - includes arterial injury
      • N (added to above) - includes injury to the nerve

Causes of Knee Dislocation or Dislocated Knee

It is usually rare to have a knee dislocation or dislocated knee. After a major trauma is when knee dislocation or dislocated knee happens: car crashes, other injuries involving high-speed. The look of the dislocated knee will be deformed. The straight usual line of the leg will have angulations or crookedness. In some cases a dislocated knee relocates (restore its position) on their own. Swelling and pain will occur in the knee. Despite the knee relocating, tearing (damage) of the knee ligaments occurs.

Other causes of knee dislocation or dislocated knee may be sporting tackles or falls. There is considerable soft tissue damage in knee dislocation or dislocated knee, especially to the ligaments supporting the joint. The ACL (anterior cruciate ligament) and PCL (posterior cruciate ligament) are most often always torn, along with likely damage to the MCL (Medial collateral ligament), LCL (lateral collateral ligament) and cartilage. Other serious complications of knee dislocation include nerve and blood vessel damage. A dislocated knee or knee dislocation should be differentiated from a subluxation. Subluxation is a condition where there is a partial dislocation of the bones and the bone separation is very mild and they can move back together.

Knee Dislocation or Dislocated Knee Treatment

Some of the common causes of knee dislocation or dislocated knee are:

      • Collision of motor vehicles causing trauma to the knee can cause knee dislocation or dislocated knee.
      • Auto-pedestrian impact
      • Falls
      • Industrial injuries
      • Athletic injuries are very common cause of knee dislocation or dislocated knee.

Signs and Symptoms of Knee Dislocation or Dislocated Knee

There will be symptoms of severe pain due to knee dislocation or dislocated knee. There can also be symptoms of no feeling under the knee sometimes. Any movement will be painful in the instance that the knee relocates, due to swelling accrued from fluids. Loss of movement or feeling below the knee or loss of impulse is the serious symptoms that occur in knee dislocation or dislocated knee.

      • A traumatic injury causing abrupt, intense pain.
      • Deformity of the joint.
      • Symptoms of immediate swelling on knee dislocation or dislocated knee.
      • Instant bruising.
      • Patient with dislocated knee will experience symptoms of inability to move the knee.
      • Inability to bear weight.
      • If there are symptoms of numbness in the lower leg or foot due to knee dislocation or dislocated knee, it signifies nerve damage.

Symptoms of absence of pulse in the foot, or a pale, cold foot signifies blood vessel damage.

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Written, Edited or Reviewed By:

, MD, FFARCSI

Last Modified On: May 3, 2016

Pain Assist Inc.

Pramod Kerkar
  Note: Information provided is not a substitute for physician, hospital or any form of medical care. Examination and Investigation is necessary for correct diagnosis.

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