This can severely harm the ligaments, tendons, and other soft structures that support the knee joint. Knee dislocations are relatively rare but can potentially be very serious and have long-lasting effects on the knee joint that are detrimental, if not treated promptly and properly. 

A knee dislocation is not the same as an acute patellar dislocation, dislocated kneecap, or an unstable kneecap/subluxing patella. Knee dislocation can be a devastating injury by comparison and would require immediate medical intervention. 

Knee dislocations are categorised into different levels based on the degree of displacement of the bones and the severity of the related soft tissue injuries. 

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There are several classification systems, but one commonly used method is the Schenck classification:

• Grade I: partial dislocation with no damage to the ligaments or other soft tissues supporting the knee joint.
• Grade II: partial dislocation with damage to one or more ligaments or soft tissues, but without complete disruption of the joint.
• Grade III: complete dislocation with damage to multiple ligaments and soft tissues, but without any significant bone fractures or vascular injuries.
• Grade IV: complete dislocation with damage to multiple ligaments and soft tissues, as well as associated bone fractures or vascular injuries.

Additionally, knee dislocations can also be classified based on the direction of the dislocation (anterior, posterior, lateral, or medial) and the presence of associated injuries, such as nerve or blood vessel damage. The severity of the dislocation will determine the course of treatment, with more severe cases often requiring surgery and a longer recovery time.

The following are some of the most prevalent causes of knee dislocations:

• High-energy traumatic injuries such as falls from significant heights and traffic collisions
• Direct impact or trauma to the knee, stemming from sports-related activities
• Existing knee injuries such as subluxated patella
• Low-energy mechanisms such as obesity

• Acute pain in the knee
• Swelling and bruising
• Deformity or misalignment of the knee joint
• Inability to bear weight on the affected leg
• Stiffness or limited range of motion
• Numbness or tingling in the foot or lower leg
• Weakness or muscle spasms in the affected leg
• Visible injuries which may include open wounds and exposed bone

The force necessary to dislocate the knee joint can cause collateral damage to the surrounding ligaments, muscles, and other soft tissues of the knee, resulting in considerable pain and suffering. Furthermore, joint displacement can put pressure on nearby nerves, which can contribute to further pain or numbness.

These risk factors include:

• Gender: women are more prone to unstable kneecaps potentially attributed to their wider hips and increased Q angle (the angle between the thigh bone and the kneecap).
• Age: knee dislocation is common among 10-17 year olds, the likelihood attributed to rough-and-tumble play. 
• Athletes: unstable kneecap injuries may occur among athletes of contact sports such as football and basketball.  
• Medical history: individuals with pre-existing knee conditions such as previous patellar subluxation or hypermobility, have a higher risk of being susceptible to knee dislocation. Additionally, patients with obesity too, are more prone to knee dislocations.

Following that procedure, the tests below would be required to further access the injuries that have occurred: 

• Physical examination and medical history: inform your orthopaedist of the potential activities that may have led to an injury such as trauma, exercise, or sports. Physically the area of injury will be examined and several motion tests will be conducted to review the injury.

• Imaging tests: magnetic resonance imaging (MRI) would be required to provide a detailed view of the soft tissues in the knee and can help identify any tears or other damage. An x-ray and computed tomography scan (CT-scan) would be conducted to help identify any fractures or bone damage in the knee joint. 
• Diagnostic arthroscopy: Arthroscopy involves inserting a small camera into the knee joint to visualise the knee’s structure as well as assess the extent of the injury. This is usually done within 2 weeks of surgery.

• Immobilisation: the affected knee would be immobilised in a cast or brace to protect it from damage and enable the ligaments to heal.
• Medications: non-steroidal anti-inflammatory drugs (NSAIDs) and painkillers are commonly prescribed as the first course of treatment to reduce inflammation and manage pain.
• Crutches: to limit placing weight on the affected knee.
• Physiotherapy: upon discontinuation of the use of the cast or brace, an active range of motion exercise would be administered via physiotherapy to regain mobility.
• Arthroscopic surgery: necessary to repair ligament, cartilage, and meniscus damages. In certain cases, blood clot removal would also be required. Additionally, arterial injuries would call for the need for surgical repair.