Knee Dislocation

What is Knee Dislocation?

A knee dislocation is when the alignment between the upper part of the shin bone (proximal tibia) and the lower part of the thigh bone (distal femur) is lost. This can also happen if there are severe injuries involving multiple or critical ligaments in the knee. A dislocated knee is a serious injury that usually needs immediate surgery. It’s important to quickly identify this kind of injury so it can be properly examined with the right images and so the patient can be given the right surgical treatment. There are risks of complications like vascular injury and compartment syndrome when dealing with a knee dislocation. Health care professionals should be careful not to overlook these in their evaluations.

On the other hand, a dislocated kneecap (patellar dislocation) is generally less severe and usually doesn’t need immediate surgery or treatments related to blood vessels.

What Causes Knee Dislocation?

It generally takes a severe injury, like a high-energy trauma, to dislocate the knee joint where the tibia (shin bone) and femur (thigh bone) meet. When the knee joint is disrupted this way, it’s also common to have multiple associated ligament injuries and instability in the knee. This sort of injury could happen in a car accident, while playing high-speed sports, or from a fall. The knee can be dislocated in different directions – it can shift forwards or backwards, which is most common, or it can move to the side or rotate.

Risk Factors and Frequency for Knee Dislocation

Knee dislocations might not happen often, but they are serious injuries that can threaten the health of your limb. Not spotting a related vascular injury can result in prolonged lack of blood circulation to the limb, which could eventually end up in amputation. These dislocations make up a very small percentage of all orthopedic injuries.

It’s worth noting that the real rate of knee dislocations might be underreported because nearly 50% of these injuries can fix themselves at the place of the accident or could be diagnosed wrongly at the emergency department. It’s also observed that men are reported to have knee dislocations more than women with a ratio of 4:1. Moreover, obesity independently raises the risk of this injury happening from very low energy injury mechanisms.

Knee dislocations are serious and can threaten the health of your limb.
Not spotting a related vascular injury can lead to a lack of blood circulation, leading to amputation.
These injuries are a very small percentage of all orthopedic injuries.
Half of these injuries can fix themselves or could be diagnosed wrongly, leading to underreporting.
Men have more reports of knee dislocations than women, with a ratio of 4:1.
Being obese raises the risk for this injury from low energy injury mechanisms.

Signs and Symptoms of Knee Dislocation

One key aspect when examining knee dislocations is understanding how the injury happened and knowing the position of the lower leg right after the event. This becomes even more important when we consider that half of knee dislocations fix themselves spontaneously before a doctor can see them. If a patient or an emergency responder reports the leg bones had been in a position different than normal, then it’s likely a knee dislocation happened but the joint has returned to its normal position on its own. During the examination, doctors will look for minor signs of trauma like scrapes, bruises, and swelling. If the knee extends more than 30 degrees when the heel is lifted, this is a strong indicator that the knee was dislocated.

In some cases, patients reach the doctor with a clear deformity that suggests a knee dislocation. There might be a lot of swelling and bruising which can hamper the examination of the ligaments. One key sign of an intractable dislocation towards the back of the knee is when the internal part of the thigh bone pushes through the inner joint capsule creating a ‘dimple’ or ‘pucker’ effect. Doctors avoid manually fixing the joint in these cases because it could damage the skin.

All patients who might have dislocated their knee should undergo a thorough physical examination of the affected leg. It’s crucial to check the blood circulation and the stability of the ligaments in the joint.

Doctors will check pulses in the lower leg and behind the knee, comparing it to the other leg. Even if the pulses are present, doctors will repeatedly check to make sure a blood vessel injury doesn’t exist. This is because injuries to the popliteal artery, the main blood vessel running behind the knee, can be hidden by other vessels supplying blood to the area.

If doctors suspect a knee dislocation, they should measure the ankle-brachial index (ABI), a test to see if there’s adequate blood flow to the ankles. An ABI of less than 0.9 will require more tests such as an arterial duplex ultrasonography or a CT angiogram, and a consultation with a vascular surgeon. Immediate reduction of the joint is needed if the pulses are absent or weak, and surgical intervention might be necessary if the pulses do not improve. If the tests show that the limb has been without adequate circulation for over six hours, there there’s a high chance – up to 86% – of amputation.

At the same time, the doctor should test and record any nerve damage since nerve injuries may also occur in addition to vascular injuries. Assessing and noting down sensory and motor function though may be limited by pain and swelling. The stability of the 4 major knee stabilizers should also be checked.

Testing for Knee Dislocation

The Ankle-Brachial Index, or ABI, is a measurement used to compare the blood flow in the lower and upper extremities of the body. This is done by examining blood flow in the arteries of the ankle and the arm. A normal ABI result is 0.9 or more, while an ABI less than 0.9 may suggest some issues with blood flow.

However, just because you have a normal or healthy pulse or ABI, it doesn’t necessarily mean that there are no injuries. There have been cases where patients developed complications despite outwardly normal signs, therefore, it’s important not to rule out injuries based solely on these measurements.

If you have the facility, duplex ultrasonography can provide a side-by-side comparison of blood flowing in your arteries. If weak or absent pulses, discomfort in limbs, or abnormal duplex ultrasonography are seen, it is recommended that you pursue a computed tomography angiography for a more detailed view.

Also, radiographic images of the knee can help to confirm whether knee dislocation has occurred alongside any fractures through standard front and side views, and optionally, a 45-degree oblique view especially in relation to fractures. However, a normal X-ray does not discount a knee dislocation since the dislocation might have corrected itself immediately after happening.

A CT scan can offer a more comprehensive view if there are fractures revealed in the radiographs. It can provide a more detailed image of the fracture and show where it extends, especially for any fractures located in the tibial area. An MRI might be necessary for further examination of soft tissue structures and in planning treatments, ideally conducted after an acute reduction of the dislocation and before any surgical implants are placed.

Treatment Options for Knee Dislocation

If someone dislocates their knee, this is seen as an emergency that may require immediate treatment. The first step is to get the knee back into its normal position, which is called a “closed reduction”. Doctors will examine the patient’s vascular health to make sure blood is flowing correctly in the leg. If blood flow is normal, and the patient has strong pulses in their leg, frequent checks at the hospital may be the only treatment needed.

However, if there are concerns about blood flow in the leg, more tests and perhaps urgent consultation with a vascular surgeon will be needed. This is to make sure there’s no injury to the popliteal artery, an important blood vessel near the knee.

The process to correct the knee’s position differs depending on the type of dislocation. For example, an anterior dislocation requires moving the femur (thigh bone), while a posterior dislocation means moving the tibia (shin bone). When the dislocation involves a side or rotational movement, the process will involve gentle pulling and moving the knee in the opposite direction of the dislocation. After this correction, the knee is placed in a splint at a slightly bent position.

Once the knee is back in position, surgery may be used to hold it securely in its correct place, especially if there’s no vascular injury. However, remaining still and not moving for a long time can sometimes lead to other issues like an unstable knee or reduced movement.

An “open reduction” process, which is essentially surgery, may be necessary when other methods have failed, the injury is old, or there are certain types of dislocation. If the patient is obese, the closed reduction might be more difficult, and direct surgery could be an alternative. This surgery is also suggested if there’s an associated vascular injury.

The surgery itself involves an incision and the repair of any damaged tissue. If there are other injuries, such as damage to the meniscus (knee cushion), ligaments, or tendons, these can also be repaired during surgery. This surgery is also recommended when there is an open fracture-dislocation, compartment syndrome, or multiple injuries.

If the knee ligaments have been injured, they may need to be repaired or replaced surgically, which may not be possible through arthroscopy (a type of minimally invasive surgery), especially if there are large injuries. Addressing these injuries promptly can improve the results, and the patient should keep their knee stable and immobilized until this can be arranged. Both immediate and planned reconstructive surgeries have similar results.

When a doctor is trying to diagnose a dislocated knee, they have several other conditions they’ll first check to rule out. These conditions have similar symptoms to a knee dislocation and could include:

Injury to the anterior cruciate ligament (one of the major ligaments in the knee)
Fracture of the femur (thigh bone)
Other common knee fractures
Medial collateral ligament injury (damage to the ligament on the inner part of the knee)
Damage to the meniscus (a type of cartilage in the knee)
Injuries to the patella (kneecap) or a dislocated kneecap
Patellofemoral joint syndromes (conditions that affect the joint where the kneecap and thigh bone meet)
Fractures of the tibia or fibula (the two long bones in the lower leg).

Recognizing these conditions and conducting the appropriate tests will help them accurately diagnose and treat the problem.

What to expect with Knee Dislocation

A knee dislocation is a severe injury that often results in the knee not returning to its original condition before the injury. In many cases, surgical intervention is typically required.

Possible Complications When Diagnosed with Knee Dislocation

Traumatic knee dislocations can lead to a variety of complications. The most common is stiffness of the knee, known as arthrofibrosis, while the most serious is injury to the blood vessels. Injuries to the peroneal nerve and surrounding vascular structures are also common after such a dislocation.

Stiffness in the knee or arthrofibrosis, happens in up to 38% of patients with knee dislocation. Not promptly immobilizing the affected joint can increase this risk. Early movement of the joint is encouraged to prevent this. Treatment options include manipulation under anesthesia and breaking down adhesions with arthroscopy.

Up to 37% of patients experience some instability in their knee after a dislocation, but re-dislocation is not frequent. The management of this can range from wearing a brace to having revision reconstruction surgery.

Damage to the peroneal nerve in the knee happens in 10% to 40% of patients, and about half of those affected partially recover. Increased risk is linked to males, obese patients, and those with associated fractures in the fibula. These injuries are managed with a type of brace known as an ankle-foot-orthosis (AFO) to prevent foot drop. Acute injuries can be treated with nerve exploration or removal of the nerve sheath at the time of reconstruction, while chronic cases might require nerve repair or reconstruction, or transferring a tendon.

Damage to the blood vessels occurs in 5% to 15% of all knee dislocations; almost half of these injuries happen with anterior or posterior dislocations. Knee dislocations categorized as KD IV have the highest risk of vascular injury. These injuries should be treated immediately with vascular repair surgery and preventive muscle decompression procedures.

Recovery from Knee Dislocation

Recovering from a traumatic knee dislocation is a physically challenging process. While there isn’t a universal plan of action, the basic principles of rehabilitation remain the same. Medical professionals recommend a break of 1 to 3 weeks between the injury happening and surgery being performed to allow the inflammation to calm down. During this time, it’s recommended that patients do straight leg raise exercises to help avoid the wasting away of their thigh muscles.

The main aim of rehabilitation right after surgery is to protect the area that was operated on, especially if there was a reconstruction of a part of the knee called the PCL. That’s why some medical plans suggest using a brace that limits extension. The rehabilitation program after this initial recovery period is tailor-made for each patient based on the specific details of their injury and surgery.

Preventing Knee Dislocation

If your knee is dislocated, the first line of treatment usually involves using a splint or brace, or in some cases, surgery may be necessary. Following this, it’s essential to engage in rehabilitative exercises to regain muscle strength, flexibility, and functionality. It’s really crucial to understand how significant rehab is to your recovery.

There might be restrictions on weight bearing activities and alterations in your normal routine during your recovery. You might also have to use aids like crutches or braces. Doctors must make sure patients fully understand all these changes.

If there’s an increase in pain, swelling, or if you notice any changes in how you feel in the affected limb, this could mean there are complications related to your nerves or blood vessels. It’s vital that patients know the signs and symptoms of these complications, and when and how to seek medical help. Also, sticking to your rehabilitation and ongoing care plan is extremely important.

If you have experienced a traumatic knee dislocation, connecting with support groups, seeking therapy or joining a rehab group can be helpful. Such networks can provide emotional support and practical advice, helping to improve your rehabilitation experience.

Frequently asked questions

A knee dislocation is when the alignment between the upper part of the shin bone (proximal tibia) and the lower part of the thigh bone (distal femur) is lost.

Knee dislocations are a very small percentage of all orthopedic injuries.

Signs and symptoms of Knee Dislocation (Knee Popped Out) include: - Understanding how the injury happened and knowing the position of the lower leg right after the event. - Leg bones being in a position different than normal, but the joint has returned to its normal position on its own. - Minor signs of trauma like scrapes, bruises, and swelling. - Knee extending more than 30 degrees when the heel is lifted. - Clear deformity that suggests a knee dislocation, with swelling and bruising. - Internal part of the thigh bone pushing through the inner joint capsule, creating a 'dimple' or 'pucker' effect. - Checking blood circulation and stability of the ligaments in the joint. - Checking pulses in the lower leg and behind the knee, comparing it to the other leg. - Measuring the ankle-brachial index (ABI) to see if there's adequate blood flow to the ankles. - Assessing and noting down any nerve damage. - Checking the stability of the 4 major knee stabilizers.

It generally takes a severe injury, like a high-energy trauma, to dislocate the knee joint where the tibia (shin bone) and femur (thigh bone) meet.

The other conditions that a doctor needs to rule out when diagnosing Knee Dislocation are: - Injury to the anterior cruciate ligament (one of the major ligaments in the knee) - Fracture of the femur (thigh bone) - Other common knee fractures - Medial collateral ligament injury (damage to the ligament on the inner part of the knee) - Damage to the meniscus (a type of cartilage in the knee) - Injuries to the patella (kneecap) or a dislocated kneecap - Patellofemoral joint syndromes (conditions that affect the joint where the kneecap and thigh bone meet) - Fractures of the tibia or fibula (the two long bones in the lower leg)

The types of tests that may be needed for knee dislocation (knee popped out) include: 1. Ankle-Brachial Index (ABI) measurement to assess blood flow in the lower and upper extremities. 2. Duplex ultrasonography to provide a side-by-side comparison of blood flow in the arteries. 3. Computed tomography angiography (CTA) for a more detailed view if weak or absent pulses, discomfort in limbs, or abnormal duplex ultrasonography are seen. 4. Radiographic images of the knee, including standard front and side views, and optionally a 45-degree oblique view, to confirm knee dislocation and fractures. 5. CT scan to offer a more comprehensive view and detailed image of fractures, especially in the tibial area. 6. MRI for further examination of soft tissue structures and treatment planning, ideally conducted after reducing the dislocation and before surgical implants are placed. It is important to note that the specific tests required may vary depending on the individual case and the severity of the injury.

The treatment for knee dislocation, also known as a knee popped out, depends on the severity of the injury. If there are no concerns about blood flow in the leg, the knee can be put back into its normal position through a process called closed reduction. After this, the knee may be placed in a splint. Surgery may be necessary to hold the knee securely in place, especially if there is no vascular injury. In cases where closed reduction is not possible or other methods have failed, open reduction surgery may be performed. This surgery involves repairing any damaged tissue, including ligaments, tendons, and the meniscus if necessary. Injuries to the knee ligaments may require surgical repair or replacement, especially if they are large injuries that cannot be addressed through arthroscopy. Prompt treatment of these injuries is important, and the knee should be kept stable and immobilized until surgery can be arranged. Both immediate and planned reconstructive surgeries have similar results.

The side effects when treating Knee Dislocation (Knee Popped Out) can include: - Stiffness in the knee, known as arthrofibrosis, which can occur in up to 38% of patients with knee dislocation. Prompt immobilization of the affected joint and early movement of the joint can help prevent this. Treatment options include manipulation under anesthesia and breaking down adhesions with arthroscopy. - Some instability in the knee after a dislocation, which can occur in up to 37% of patients. Management of this can range from wearing a brace to having revision reconstruction surgery. - Damage to the peroneal nerve in the knee, which can happen in 10% to 40% of patients. About half of those affected partially recover. Increased risk is linked to males, obese patients, and those with associated fractures in the fibula. These injuries are managed with an ankle-foot-orthosis (AFO) brace to prevent foot drop. Acute injuries can be treated with nerve exploration or removal of the nerve sheath at the time of reconstruction, while chronic cases might require nerve repair or reconstruction, or transferring a tendon. - Damage to the blood vessels, which occurs in 5% to 15% of all knee dislocations. Almost half of these injuries happen with anterior or posterior dislocations. Knee dislocations categorized as KD IV have the highest risk of vascular injury. These injuries should be treated immediately with vascular repair surgery and preventive muscle decompression procedures.

A knee dislocation is a severe injury that often results in the knee not returning to its original condition before the injury. In many cases, surgical intervention is typically required.

Orthopedic surgeon.