Your knee is a joint that is located between your upper and lower leg. Three bones meet at the knee: femur (thighbone), patella (kneecap) and tibia (shinbone). A dislocated knee happens when the position of the thighbone relative to the shinbone becomes disrupted at the knee joint, and these three bones become out of place. This can happen due to trauma to your leg, such as from falls, sports injuries, and car accidents.
WHAT ARE THE SYMPTOMS?
Symptoms of a dislocated knee occur immediately and get worse over time. These symptoms include:
- A “popping” sound is heard when the dislocation occurs
- Severe pain in the knee, where you are unable to straighten it
- Visible deformity of the knee joint
- Instability of the knee joint
- Swelling and bruising of the knee
- Inability to carry out daily activities or sports
WHAT ARE THE CAUSES AND RISK FACTORS?
A knee dislocation is often due to trauma to the knee, such as high impact or a huge blow. This includes:
- Motor vehicle accident
Banging your knee hard into the dashboard can result in dislocation
- Sports injuries
Collisions of huge force when you get tackled, if you overextend your knee or if you land on the ground with your knee bent can result in dislocation
If you accidentally fall on a bent knee, or if you twist your knee with great force it may result in dislocation
WHAT IS THE DIAGNOSIS?
If a knee dislocation has occurred, the doctor will first reposition the joint (a procedure known as “reducing the joint“). Once reduced, the doctor will carefully evaluate the surrounding tissues, nerves, and blood vessels. Reduction is important to relieve the pressure in the surrounding area.
Once your knee has stabilized, your doctor will proceed to do a physical examination of the knee. Your doctor will focus on the area of stability and range of motion of your knee.
As the dislocated knee can cause damage to nerves or blood vessels, which could affect blood flow or your sense of touch below the knee. Very rarely, you may even lose your limb should these complications not be addressed. Examinations conducted by your doctor may include:
- Checking the pulse in several places on your leg and knee
Your doctor checks on the posterior tibial and dorsal pedal pulses, located in the region of the knee and foot. Lower pulses in the injured leg may indicate a blood vessel injury in your leg.
- Checking the blood pressure in your leg
Known as the ankle-brachial index (ABI), this test looks for changes in blood flow and compares the blood pressure measured in your arm to the blood pressure measured in your ankle. A low ABI measurement may indicate that the dislocation has disrupted the blood flow to your legs.
- Checking your sense of touch or sensation
Your doctor will assess your sense of feeling in the injured leg versus the unaffected leg.
- Checking nerve conduction
Your doctor will use tests like electromyography (EMG) or nerve conduction velocity (NCV) to check on the muscles and nerves in your leg and knee.
- Checking your skin color and temperature
If your leg is noted to be cold or changing colors, there may be blood vessel problems.
Imaging tests will be taken, such as an x-ray and MRI can help your doctor diagnose any damage to the bones, ligaments and tendons of the knee. An arteriogram (an X-ray outlining blood flow in your arteries and veins) may also be ordered to see if the knee dislocation damaged blood vessels.
WHAT ARE THE TREATMENT OPTIONS?
Treatment options for knee dislocation include both nonsurgical and surgical treatment.
If the damage to your knee is not too severe, your doctor may try to pop your bone back into place nonsurgically by pressing and moving your leg in certain ways. You will be sedated during this process. After your bone is back in the joint, you will be required to wear a splint for a few weeks to immobilize your knee, allowing it to heal without moving or bearing any weight.
If your dislocation has resulted in other damages or injury, such as broken bones, torn ligaments or damaged blood vessels, arthroscopic knee surgery will be required.
WHAT IS THE RECOVERY PROCESS AFTER A KNEE DISLOCATION?
The recovery period will depend on how serious your injury is and whether you had damage to your blood vessels and nerves. Typically, you will be using a knee brace or splint to keep your knee in place and allow it to heal. Thereafter, physiotherapy will be recommended to help you regain muscle strength and restore range of motion in your knee.