Knee dislocation is a rare but extremely serious injury in which the thighbone (femur) and shinbone (shinbone) lose contact with each other. A knee dislocation is different from a patellar dislocation where only the kneecap is dislodged from the groove at the end of the femur.
The most common symptom of a knee dislocation is marked swelling and deformity of the knee. The lower extremities often appear shortened and misplaced, and any movement of the joint can cause extreme pain.
About half of all knee dislocations are repositioned before reaching the hospital. This is problematic because it can lead to a greater risk of injury and complications, including:
- Compression or injury to the peroneal nerve that runs along the outer edge of the lower leg
- Rupture or blockage of the popliteal artery and vein at the back of the knee
- Development of deep vein thrombosis (DVT)
The chance of amputation was 86% if the blood vessel blockage was left untreated for more than 8 hours, and 11% if treated within 8 hours.
Knee dislocations are often the result of high-impact injuries, such as car accidents, serious falls, and sports injuries.
Knee dislocation should not be confused with subluxation, which is a partial dislocation of the knee that “dislocates” due to damaged ligaments. Knee dislocation is a more serious injury in which the dislocated bone must be repositioned into place. In subluxation, the bone “slips back” into place.
Unusual twists or mistakes can also lead to a knee dislocation. That being said, whatever the reason, the same concerns exist.
Rapid responses are invariably required to prevent serious or even devastating damage to the knee and lower extremities.
If a knee dislocation occurs, the joint is usually repositioned (a procedure called “joint reduction”) upon arrival at the emergency room. Once reduced, a healthcare provider will carefully evaluate surrounding tissue, nerves, and blood vessels.
Due to the extreme nature of the injury, the surrounding ligaments are always damaged. In almost every case, the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are torn or ruptured. In addition, collateral ligaments, cartilage, and the meniscus (the membrane between bone and cartilage) may also be damaged.
X-ray or computed tomography (CT) scans will be used to assess the nature and location of the misaligned bones. Magnetic resonance imaging (MRI) – a technique to better visualize soft tissue – can be used to describe damage to ligaments, cartilage and tendons before surgery.
To evaluate blocked blood vessels, your healthcare provider may order a CT angiogram, in which an iodine-based dye is injected into a vein to map blood flow. Doppler ultrasound can also be used to assess arterial blood flow.
Nerve damage occurs in about 25% of knee dislocations, It can initially be assessed with a physical examination to check for abnormal sensation (numbness, radiating pain) or internal (varus) or external (valgus) foot movement disorders.
In the early stages of treatment, medical care is focused on minimizing any damage to blood vessels or nerves. When these issues are resolved and stabilized, attention can be turned to structural tissue damage.
In almost all cases, surgery is required, usually to repair multiple ligamentous injuries, meniscus tears, and cartilage damage. Arterial damage may require direct repair of the affected vessel (using a synthetic patch, graft, or graft vein), arterial bypass, or thrombectomy to remove the clot.
Surgery can be done as an open procedure (using a scalpel and a large incision) or arthroscopically (using an endoscope, tubular instruments, and a keyhole incision).
Nerve damage may require the expertise of a neurosurgeon. In fact, it is not uncommon for a knee dislocation to require multiple surgeries. There are also efforts to restore lost cartilage through advanced techniques such as cartilage implants or cartilage grafts.
Complications of knee dislocation surgery, including chronic stiffness, instability and postoperative neuralgia. Joint deformities and infections are also possible.
Adherence to an extensive physical therapy and rehabilitation program is critical to restoring near-normal to normal knee function.
Knee dislocations, although serious, are extremely rare, accounting for less than 0.5% of all joint dislocations.While most people with a dislocated knee will seek emergency care due to the extreme nature of the injury, any self-healing efforts should invariably be avoided.
Delayed treatment can lead to tissue atrophy, resulting in shortening of the ruptured ligament. Not only does this make repairs difficult, but it ends up severely limiting the knee’s range of motion.
Also, waiting until the morning to “see if things improve” can lead to widespread tissue death (necrosis) due to restricted blood flow. At a stage, the injury can be so severe that above-knee amputation is required.
For this reason, any knee injury should be checked immediately if there is severe pain, swelling, redness, bleeding, or limited mobility.
Frequently Asked Questions
Is a knee dislocation the same as a patellar subluxation or dislocation?
Will not. A knee dislocation occurs when the femur and tibia no longer connect at the knee joint. Patellar subluxation is when the kneecap slips slightly out of its normal position. This is considered a partial dislocation of the kneecap. Patellar luxation is when the kneecap is completely out of position.
How common is a dislocated knee?
A dislocated knee is a relatively rare injury. Less than 1% of knee injuries are dislocations, and less than 0.5% of dislocated joints occur in the knee.
What can cause a dislocated knee?
A knee dislocation is a serious injury, usually caused by a high-intensity impact, such as a car accident, sports injury, or a serious fall.
Can you walk on a dislocated knee?
No, a dislocated knee is a very painful injury. If you dislocate your knee, you won’t be able to put weight on the joint or walk.
How long does it take for a dislocated knee to heal?
A dislocated knee is a serious injury that can take up to a year to heal. In most cases, surgery is needed to repair the ligaments and cartilage in and around the knee. After surgery, physical therapy is needed to restore the knee and work to restore normal knee function.