Knee Dislocation - Types, Causes, and Treatment

Introduction:

Knee dislocation is an emergency medical condition occurring due to the loss of connection between the tibia and femur as a type of isolated injury; the fibers involved are either the anterior cruciate ligament or the posterior cruciate ligament. The knee dislocation is assumed to be a sustained or prolonged injury when all three ligaments are involved. The dislocation of the knee can be critical and requires emergency management with proper medical history, investigation, diagnosis, and treatment plan. Knee dislocations can be a complicated injury related to significant short-term complications, such as nerve and blood vessel injuries, and long-term complications, like deteriorating joint conditions.

What Are the Types of Knee Dislocation?

Knee dislocations can be broadly classified into two types: one based on the anatomy of the injury and the other based on the force felt on the injury.

Based on the Anatomical Position of the Injury:

1. Anterior dislocation.

2. Posterior dislocation.

3. Lateral dislocation.

4. Medial dislocation.

5. Rotatory dislocation.

6. Posterolateral dislocation.

Here, anterior knee dislocation is the most common dislocation. About 40 % compared to all the other traumatic knee dislocations. The next most common is the posterior knee dislocation, occurring in around 33 % of traumatic knee dislocations.

Based on the Force Felt on the Injury:

It is categorized based on the power of impact felt on the damage, classified as high-velocity and low-velocity injuries.

How Is a Knee Injury Caused?

Knee dislocations are always associated with disruptions to the fibrous ligament. The knee is supported by four fibrous ligaments that stabilize the knee joint, called anterior cruciate, posterior cruciate, middle collateral, and lateral collateral. A knee dislocation can collaterally damage these associated fibers and vice versa. An excessive movement to the knee during extension causes anterior knee dislocations in almost 40 % of the cases, where the cause of posterior dislocation in 33 % of cases is the anteroposterior force in conditions like dashboard injury, and 18 % of the patients report lateral injury due to fractures of the tibial plateau. Knee injury occurs when there is any sudden movement or excessive strain with increased weight on the knee; this weakens the knee and compromises the adjacent soft tissue, making it unstable to function and causing distortion.

What Are the Causes of Knee Dislocation?

Knee dislocation injuries can be risky enough to lose a limb. The leading cause of knee dislocation is highly intense traumatic injuries, motorcycle accidents, falling from greater heights, and sports injuries. Obese persons also fall under the high-risk category due to increased load on the knee.

What Are the Signs and Symptoms of Knee Dislocation?

The signs and symptoms associated with knee dislocation, which is most commonly seen post-trauma, are:

• Extreme pain.

• Swelling.

• Effusion around the joint.

• Ecchymosis.

• Knee instability or deformed knee.

• Loss of integrity of the ligaments.

• Extension of the knee is seen to be more hypermobile than usual.

What Are the Effects of Knee Dislocations?

Knee dislocations can be complicated and commonly seen as sports injuries. The most observed complications are both acute and chronic; the acute injuries include:

• Irreducible knee dislocation.

• Open knee dislocations.

• Injuries to the blood vessels.

• A weak, unstable knee.

• Compartment syndrome.

• Chronic knee dislocations.

What Are the Associated Injuries of Knee Dislocation?

The typical soft tissue injuries associated with knee dislocation are injuries affecting the popliteal artery and common peroneal nerve, showing around a 20 to 25 % incidence rate.

How Is Knee Dislocation Treated?

Suppose the dislocation does not resolve soon after the injury. In that case, it is treated in three stages from the onset of the injury and classified as immediate, intermediate, and late management.

• Immediate Management: The patient is put on medications for pain and sedation, and the dislocated knee is reduced to its original position and is stabilized temporarily using splints and bandages. The distal and popliteal pulses are monitored, and injuries for any associated soft tissues are also treated. The limbs are checked for motor and sensory functions to rule out ischemia or compartment syndrome.

• Intermediate Management: This procedure is performed based on the concept that early invasive or surgical treatment brings out a better outcome, so repair of all the injured ligaments is done along with the repair of the capsule and its adjoining fibers by reattaching and fixing the mobile structures with plates and splints. In cases with an extensive injury involving tendon damage, grafts like allografts, synthetic grafts, and composite grafts are used.

• Late Management: Involves physiotherapy and rehabilitation, giving the patient a period to heal and restore normal physical activities. Periodic checkups achieve this with orthopedics and by following proper physical exercises.

How Is Knee Dislocation Diagnosed?

Knee dislocation is diagnosed using several methods:

• Ankle-Brachial Index (ABI): The ankle-brachial index is a ratio taken by measuring the systolic pressure of the leg with the arm. The pressure is recorded using a Doppler wand and a blood pressure cuff. The average ABI value ranges from 1.0 to 1.4, and any value below 0.9 shows a compromised value in vascular flow; a common ABI value does not always rule out injury and, at times, can give a false positive result.

• Duplex Ultrasound: Duplex ultrasound is used to measure the flow of blood in the limbs, its velocity, and the structure of the veins at the bedside, making it convenient for the patient.

• Radiographs (X-Rays): It is the most conventional and first line of examination; anteroposterior and lateral radiographs are taken to determine the type of dislocation that occurred.

• Magnetic Resonance Imaging (MRI): Conventional magnetic resonance imaging (MRI) examines soft tissue injuries and associated ligament, tendon, or capsular damage; it is used for preoperative planning and determining the prognosis.

• Computed Tomography(CT): This examination shows the positioning of the popliteal artery and hematoma in the posterior fossa and adjoining soft tissues.

What Are the Commonly Occurring Conditions Similar to Knee Dislocation?

A few other clinical conditions correlate similarly with knee dislocation features and symptoms. They must be ruled out carefully for proper diagnosis before developing a treatment plan. Those clinical conditions include:

• Meniscus injury.

• Medial collateral ligament injury.

• Patello femoral joint syndromes.

• Knee fracture management.

• Tibia fibula fractures.

• Femoral shaft fractures.

• Anterior circulate ligament injury.

Conclusion:

Knee dislocation is one of the most common emergency conditions, requiring a multidisciplinary approach to manage it. The associated departments involved in treating a knee dislocation include the orthopedic department. They are the first line in diagnosing, managing, and preventing this condition; a vascular surgeon rules out any damage to the blood vessels and prevents the loss of the functional nature of the knee. A radiologist consults for imaging and diagnosis. This condition can become a chronically weak and painful knee issue when left untreated. Hence, it is essential to treat the patient at the right time with the help of all three departments functioning collaterally to fix and restore the knee to perform better long-term results.