Knee injuries often occur after a twisting injury or a direct impact injury to your leg. Some injuries cause only mild swelling. Some knee injuries will cause loss of motion. After an injury, if you can not straighten your leg or knee, there is a chance that you have sustained a serious knee injury. If an athlete is unable to straighten their knee after a serious knee injury they should consider seeing an Orthopedic Surgeon.
After an injury, there are a few reasons why you might not be able to straighten your knee. Often times you can’t straighten the knee simply because of pain and swelling. Here is a list of other knee injuries which can make it difficult to straighten your knee.
Why Can’t I Straighten My Knee?
- Meniscus tear. Specifically a bucket handle tear of the meniscus. This is a unique tear where the torn piece of meniscus flips into the center of the knee joint. This torn piece then locks your knee and prevents it from straightening.
- ACL tear. Many athletes with an ACL tear will find it painful to straighten the knee. The knee isn’t locked, but it hurts too much to straighten it out. Within a few days of tearing your ACL the swelling will start to diminish and you will likely be able to straighten your knee. Sometimes athletes who tear their ACL will also tear the meniscus too. This is another reason why it will be hard to straighten the knee. Your next steps if you think you have an ACL tear are discussed here.
- Swelling. There are many reasons why your knee might be swollen. We explore the common causes of knee swelling here. Swelling is common after severe injuries due to bleeding. That can cause enough inflammation and pain that straightening the knee is simply too painful.
- Patella or kneecap dislocations: Patella dislocations are far more common than previously thought. If you felt or heard a loud clunk in the front of your knee while turning or you were hit hard in the front of your knee then it is possible that your kneecap came out of place and went back into place on its own. After the injury you may find it difficult to straighten the knee due to pain. This post on patella dislocations goes into far more detail.
- Tendon Injuries: Injuries to the quadriceps or patella tendon will affect your ability to straighten the knee. If one of those two strong tendons are torn then you will not be able to straighten your knee. You will also notice significant weakness. Patella tendon and quadriceps tendon injuries are more common in professional sports and adult weekend warriors. They are very rare in high school and collegiate sports.
If you have suffered an injury to your knee and you are unable to straighten it then there is a good chance that you have sustained a severe knee injury. This is one of those times when it is wise to see an Orthopedic Surgeon sooner rather than later to determine what the diagnosis is and why you can’t straighten your knee.