What is a Hyperextended Knee?

Medically Reviewed by Ross Brakeville, DPT on June 18, 2023
Written by WebMD Editorial Contributors
4 min read

A hyperextended knee — or knee hyperextension — develops when the knee joint bends the wrong way and can damage the ligaments in the knee. The condition is common in athletes who play high-impact sports. It can be treated using methods including rest, pain medication, and sometimes, surgery.

Symptoms of a hyperextended knee include the following:

  • Knee Pain. You may feel mild to severe pain in your affected knee.
  • Poor Movement. You may find straightening or flexing your affected knee to become difficult.
  • Swelling. Swelling and stiffness may develop around your affected knee.
  • Poor Stability. Your affected knee may feel weak, making it difficult for you to walk or stand.

In severe cases, you may get a sprained ligament near the knee. The primary ligament that could become sprained is the ACL (anterior cruciate ligament). 

Your knee is said to have hyperextended when your knee joint bends backward and this causes tissue damage and swelling. Most of the damage happens in the ACL and the PCL, which are the two ligaments in the middle of the knee. These ligaments connect the shinbone to the thighbone and help check the movement of your knee.

A bad fall or a bad landing after a jump can cause a hyperextended knee. While this condition can affect anyone, athletes are more likely to perform activities that damage their ligaments. This is because knee hyperextension is often triggered by a direct hit to the knee when playing high-impact sports like gymnastics, basketball, and soccer.

Female athletes have a higher chance of getting an ACL injury. Also, people with weak muscles or previous knee injuries or those overweight or obese may also have such knee problems. 

Knee hyperextension can also cause small pieces of bone being broken off the main bone in young children.

To check if you have a hyperextended knee, your doctor will perform a physical exam: the doctor will ask you to bend your knee at different angles as they apply pressure and check for movement. They'll use a needle to drain your knee if it's tense or swollen with joint fluid or blood. Your doctor may also ask you to get an x-ray to understand if you've broken any bones and an MRI scan to check for injuries to the ligament.

Based on the results of these tests, your doctor may diagnose you as having a sprained ligament. In severe cases, the ligament is either partially torn or split into two pieces. More severe sprained ligaments often require surgery.

You can follow these treatment measures to heal a hyperextended knee:

  • Rest. Take a break from sports and physical activities.
  • Ice. Ice your hyperextended knee to help reduce swelling.
  • Medication. You can take anti-inflammatory medication to reduce pain. 
  • Lift the leg. Keep the leg elevated above the heart when possible.
  • Compression. Use a compression wrap to reduce swelling.
  • Brace. A knee brace may reduce stress on injured structures while healing. 
  • Maintain motion.  Keeping the knee still longer than 2-3 days increases the risk of long-term stiffness and other complications”.  
  • Physiotherapy.  Prescribed activities to minimize further damage and maximize recovery

If you have a severe sprain, you may need ligament repair surgery, where a piece of tendon from somewhere else, such as your hamstring is taken and used to replace the damaged ligament.

While healing from this surgery, you will need to do physiotherapy to include exercises to help strengthen the leg muscles. You can also wear a knee brace to improve joint stability as you recover.

In more than 80% of cases, ACL surgery, along with physiotherapy, fully restores knee functionality. Your doctor may recommend further ligament surgeries if the first attempt is unsuccessful. However, later surgeries can be more difficult and have poorer long-term results.

Overall, some pain and swelling can remain after this surgery. This may be the case if other knee injuries, like a tear in the cartilage, have happened at the same time as the knee hyperextension.

In some cases, better motion at the knee joint after surgery can have good results. This is because the tendon used to replace the torn ligament will stretch over time. Surgery comes with a small chance of getting an infection, long-term knee stiffness, and blood clots in the leg. 

In any case, even minor knee injuries can increase your chance of getting another knee injury in the future. To lower this risk, you can join injury prevention programs.

Your expected recovery time depends on the severity of your injury, but physiotherapy can help speed things up. Keep in mind that the recovery time for each person is different.

Mild sprains often feel better after two weeks of normal treatment measures like rest. But, recovery from ligament repair surgery takes around six months. Your doctor will advise you to see a physiotherapist for port-op management. You might be able to resume sports only after six months.

If you start to use your knee before it's fully healed, you could cause permanent damage.