What is Hyperextended Knee?
Injuries to the knee joint are commonly seen in athletes who participate in high intensity activities. These injuries cause inflammation and pain of the knee joint. Hyperextended knee is one such example of these types of injuries. Hyperextended knee is a condition where the knee ligaments get stretched beyond their normal range of motion.1
Pathophysiology of Hyperextended Knee
One of the most complex joints in the body is the knee joint. The knee joint serves as a connection between the thigh bone (femur) and shin bone (tibia). The smaller bones present with tibia and the kneecap (patella) make up the knee joint. Tendons connect to the leg muscles and allow movement of the knee joint. The ligaments help in joining the knee bones and help with the stability of knee joint. Knee joint is an example of a bicondylar synovial joint. Flexion and extension along with a small degree of medial and lateral rotation are the movements which can be done with the knee joint.
In the case of a hyperextended knee, the knee joint ligaments get stretched or pulled beyond their capacity or limits. This causes tear or strain in the ligament. The damage incurred depends on the degree of the injury. The patient may not be able to weight bear on the affected leg when the knee is recovering.
Causes of Hyperextended Knee
When the knee joint is pushed or forced to bend backwards, then it causes hyperextended knee. This can occur after the patient has had a wrong landing from after a jump or fall from a ladder. Hyperextended knee is often seen in athletes who play sports which involve making sudden twist or turns and stopping immediately. Some of the examples of such sports are basketball, volleyball, football and gymnastics. Vehicle accidents can also cause hyperextension of the knee joint after a direct force or blow to the knee leading to damage to knee ligaments with a possible kneecap dislocation.
Signs & Symptoms of Hyperextended Knee
Pain: Patient feels symptoms of pain in the knee joint after hyperextension of the knee joint.2 Pain can be mild to severe and is severe where there is damage or tear to the ligaments or other structures. Pain can be felt as a mild ache to a sharp pain in the back of the knee or it can be felt as a pinching pain in anterior part of the knee joint. At the time of injury, patient also may hear a popping sound, which occurs as a result of overstretching of the ligaments beyond their normal range of movement.
Knee Instability: After a hyperextension knee injury, patient experiences symptoms of instability in the knee joint and feel as if their leg is “giving out” when walking or find it difficult to stand on one leg.
Reduced Mobility: Patient has decreased mobility with knee range of motion, such as difficulty in bending or straightening the leg after a hyperextension injury. Decrease in mobility can be from swelling around the knee, which limits the range of movement of the joint. The degree of reduced mobility also depends on the amount of damage to the internal structures, such as the PCL, ACL, meniscus or popliteal ligament.
Swelling & Bruising: Patient can have immediate or delayed bruising and swelling of the knee and its surrounding area. The swelling and bruising can be mild or severe. This is the body’s method of responding to the injury to the tissues.
Diagnosis of Hyperextended Knee
The mechanism of the hyperextended knee injury is important to assess which area of the knee joint is damaged. Physical examination is conducted where the affected knee joint is checked to look for any swelling or bruising in the area.
Palpation of the knee and the surrounding muscles is done to look for tenderness. The doctor also performs range of motion movements to assess the severity of the damage to the knee joint.
Imaging Tests such as x-ray or Magnetic Resonance Imaging (MRI) scan helps in better visualization of the knee joint. The x-ray helps in detection of any broken bones and MRI scan helps in assessing any injuries to the ligaments and the surrounding knee structures.
How is Hyperextended Knee Treated?
If the damage to the knee joint is less, then conservative treatment, such as pain medications and rest is sufficient for recovery of hyperextended knee. In mild cases of hyperextended knee and with conservative treatment, recovery time is around 2 to 3 weeks.
Conservative Treatment of Hyperextended Knee
Rest: Patient with hyperextended knee should take complete rest and stop playing sports for a while. High impact or high activities and contact sports should be avoided. Mild range of motion exercises should be done. NSAIDs, such as naproxen and ibuprofen, help in decreasing the pain and swelling associated with hyperextended knee. Crutches can be used to minimize weight bearing.
Ice: Ice application to the affected knee joint for about 20 minutes every couple of hours helps in relieving pain and swelling associated with hyperextended knee. The ice should always be wrapped in a towel to prevent skin irritation and should never be applied directly to the skin.
Compression for Hyperextended Knee: Elastic bandage or a compression wrap can be used to reduce swelling and pain.
Elevation: Keeping the affected leg elevated above the level of the heart helps in reducing the swelling caused due to Hyperextended knee. The leg can be placed on a pillow when sleeping or sitting up.
Surgical Treatment of Hyperextended Knee
If the knee hyperextension causes tear or rupture of the tendon, then surgery may be needed to repair it. One of the most common tendon injuries of the knee joint is ACL or anterior cruciate ligament rupture. These occur in extreme hyperextension of the knee joint. Injuries to the posterior cruciate ligament (PCL) and popliteal tendon can also occur with a hyperextended knee and require surgery for repair. If the cause of hyperextended knee is a serious injury which causes damage to the meniscus, then also surgery may be needed for repair.
Rehabilitation & Recovery: After the surgical procedure, the patient will need to undergo rehabilitation program to strengthen the knee. Recovery from surgery for hyperextended knee can take up to 9 months. Patient needs to follow the complete rehabilitation program to improve the strength and flexibility of the knee muscle after the hyperextended knee injury.