Hyperextension of the knee, also known as “genu recurvatum” occurs when the leg excessively straightens at the knee joint, putting stress on the knee structures and the back of the knee joint.
Hyperextension of the knee can occur to anyone, but it’s more common among athletes, especially those who play sports like football, soccer, skiing or lacrosse. It’s often the result of a direct blow to the knee or forces generated during a quick deceleration or stop. According to the American Journal of Sports Medicine female athletes have increased joint instability, putting them at a greater risk of knee injury than men, especially those who participate in the high-risk sports.
During hyperextension, the knee joint bends the wrong way, which often results in swelling, pain and tissue damage. In severe cases, ligaments such as the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), or popliteal ligament (the ligament along the back of the knee) may be sprained or ruptured.
Instability of the knee
After a hyperextension injury you may notice instability in your knee joint. Many people report feelings of their leg “giving out” while walking or difficulty standing on one leg.
Localized pain in the knee joint is expected after hyperextension. Pain can vary from mild to severe and usually increases when ligaments or other structures are damaged or torn. Pain is described as a mild ache to a sharp pain in the back of the knee or a pinching pain in front of the knee joint.
You may have difficulty bending or straightening your leg following a hyperextension injury. This could be due to swelling around the knee, which can limit how far you can move it, as well as damage to the internal structures such as the ACL, PCL, popliteal ligament, or meniscus.
Swelling and bruising
After an injury you may notice immediate or delayed swelling and bruising of the knee and surrounding area. This can be mild or more severe, and it is your body’s way of responding to the injured tissues.
Like many other soft tissue injuries, it’s advised to follow the RICE principle following knee hyperextension.
Stop the activity that caused injury and seek medical attention. Take a break from any high-intensity or high impact activities and avoid any contact sports. Gentle range of motion exercises are best at this time. Anti-inflammatory medications can be helpful to decrease swelling and pain.
Ice the affected knee for 15 minutes multiple times per day. Ice can help bring down swelling and manage pain. Always place a piece of fabric or a towel between the ice and your skin to prevent skin irritation.
Compression of the knee with a compression wrap or elastic bandage can help manage swelling and reduce pain.
Try to elevate your leg above your heart whenever possible. Lie in bed with your leg on a pillow or while relaxing in a recliner chair.
Although less common, knee hyperextension can also result in a tendon tear or rupture. ACL ruptures are the most common tendon injury of the knee and can occur with extreme hyperextension. PCL and popliteal tendon injuries can also happen with hyperextension and may require surgical repair as well.
Other structures of the knee like the meniscus can sustain injury during a serious blow, and it’s not uncommon for multiple structures to be damaged at the same time.
Recovery from a mild to moderate sprain following a knee hyperextension injury can take 2 to 4 weeks. It’s important during this time to limit activities that can further strain the knee and to continue to manage swelling and pain.
Surgical reconstruction of an injured ligament often leads to full recovery and return to function in a high percentage of cases. It’s considered the gold standard for ACL injuries but often brings with it a long recovery time of 6 months or more.
Physical therapy is necessary to increase strength and rehabilitate the knee and surrounding muscles to pre-injury condition and can help reduce recovery time.
According to an article in Joints, other patient factors like age, gender, weight, mechanism of injury and surgical technique can also influence recovery time.
Knee hyperextension injuries can vary from a mild strain to a severe tendon injury. People who engage in high impact sports are at an increased risk of knee hyperextension and tendon rupture.
Prevention of knee hyperextension involves maintaining adequate strength in the muscles surrounding the knee, particularly the quadriceps as well as including a proper warm up and cool down before and after every workout or athletic event.