Giving Way (Instability)
If it feels as if your knee was going to give out from underneath your body, you should seek medical help for further evaluation. Giving away may be due to five major reasons.
The first is a tear of your cartilage rings called menisci. This type of giving away is usually a feeling of instability of your knee especially with squatting or descending stairs.
The second is due to a tear of your cruciate ligaments located in the center of your knee. This is more of a true giving away with an actual buckling of your knee. Most people have had some sort of major injury to their knee associated with this condition. Most can recall a "pop" of the knee and significant swelling at the time of the injury. If this is occurring often, you can usually predict when it is going to happen such as rapid pivoting or cutting movements. Click here to learn more about ACL tears.
The third reason that your knee could give way is because you have a tear of your collateral ligaments. There are two major collateral ligaments - the MCL (on the inside of your knee) and the LCL (on the outside of your knee). Your MCL is the one most commonly torn, and sometimes it tears when the ACL does as well.
The fourth reason is usually due to problems with your kneecap (patella) moving out of its groove on the femur. This is usually associated with a sudden click to the kneecap and a feeling of it going back into the groove. This is called patellar instability.
The fifth reason is usually due to the catching of the uneven surfaces of your joint from arthritis. The grooves and dips in your worn cartilage catches and produces a feeling of giving away. These episodes are unpredictable, but can occur with attempts at squatting or getting up from a chair. Occasionally a free-floating piece of calcified cartilage called a loose body or a "joint mouse" may become caught in your joint producing a giving away or locking feeling.