Knee Pain Symptoms - Instability - Giving Out

knee instability
Knee instability occurs when the knee gives out. Courtney Keating / Getty Images

The symptom of a knee giving out is most often due to a ligament injury. The knee is held together by ligaments, and the sensation of instability, or the knee giving out, is often due to an injury to one of the knee ligaments.  Ligaments are structures that connect two bones.  There are four major, and many secondary, knee ligaments.

Injuries to one or more of the knee ligaments can lead to the bones not being held tightly enough in position.

Usually symptoms of knee instability are noticed with twisting or side-to-side movements. This may occur in sports activities, or may occur with simple tasks such as twisting your knee to get in and out of a car.

Types of Ligament Injuries

Each of these ligament injuries can cause the knee to feel unstable. 

Non-Ligament Causes of Instability

It is also possible for people to experience instability symptoms with injuries that cause knee pain. Often the body protects itself from pain with involuntary movements. This may 'feel' as though the knee wants to give out, causing a sensation of instability, but it is not due to a ligament injury as described above.

The best way to tell the difference between instability caused by a ligament injury, versus a sensation of instability, is by having your knee examined by a skilled physician.

  There are tests used to determine the function of each ligament.  For example, the Lachman's test is used to test the anterior cruciate ligament.

Treatment of Instability

There are both surgical and non-surgical treatments for knee instability.  Non-surgical treatments can include physical therapy to strengthen the muscles around the knee joint and knee braces to better support the knee joint.

  Surgical treatments generally involve repairing or reconstructing the damaged ligament to restore the normal structure of the knee joint.  The most common type of ligament reconstruction is for ACL tears.

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