When you fracture or dislocate your knee, it may look twisted, bent out of shape, or out of its normal position. This type of injury may also cause:

• Severe pain.
• Swelling and bruising.
• A feeling that a bone popped or moved out of place.
• A loose or unstable knee joint. You may not be able to stand or walk.
• Abnormal movement of your leg or knee.
• A locked knee (can't bend or straighten it).
• Cool, pale skin or numbness and tingling at or below the injury, if nerves or blood vessels were injured or pinched by the injury.

Fracture

A fracture of the knee may mean that you have broken one of the following bones:

• Kneecap (patella)
• Lower end of the thighbone (distal femur)
• Upper portion of one of the lower leg bones (tibial plateau, tibial spine, or fibular head)

Knee fractures are most commonly caused by abnormal force, such as a falling on the knee, a severe twisting motion, severe force that bends the knee, or when the knee hits an automobile dashboard. Indirect injury, such as a forceful contraction of the thigh muscle, is less common.

Dislocation

It is much more common to dislocate the kneecap (patella) than the knee joint. The kneecap is more likely to dislocate when the:

• Knee is in a bent (flexed) position and turned outward.
• Side of the kneecap is hit, forcing the kneecap toward the outside of the leg.
• Knee is swollen.

It takes more force to dislocate a kneecap the first time. Once you have dislocated your kneecap, it will be more easily dislocated by another injury or a repeat of the forces that dislocated it the first time.

Dislocation of the knee joint is rare and requires great force. A dislocated knee, even if it goes back into place by itself, is a serious injury that requires emergency treatment.

Medical treatment

Immediate medical treatment may involve:

• Putting the bone back in place if it hasn't already popped back into place.
• Splinting the joint or limb.
• Applying cold packs.
• Elevating the injured area.

A fracture or dislocation of the knee requires medical evaluation.