Knee weakness, stiffness, decreased movement, or locking

You may not be able to bend or straighten your knee after an injury, especially if your knee is swollen. When the swelling goes down, normal movement will usually return.

Pain may make your knee and the muscles around it feel weak, but you should still be able to move them.

Your muscles may sometimes feel weak or stiff, especially after a strenuous workout. This usually means you have overexerted yourself.

Other causes of weakness, stiffness, or decreased movement include:

• Damaged muscles, tendons, bones, or nerves.
• A dislocated kneecap.
• Another medical condition, such as arthritis.

Your knee may lock if you have a more serious problem-such as a free-floating piece of bone, cartilage, or a foreign object in a joint (loose body)-or a tear in the shock-absorbing disc that cushions the knee (torn meniscus).

Treatment depends on the cause of your symptoms, your age, and other health conditions.