Call for emergency medical help. If you suspect you're having a heart attack, don't hesitate. Immediately call 911 or your local emergency number. If you don't have access to emergency medical services, have someone drive you to the nearest hospital.
The most common causes of knee weakness are osteoarthritis, sprain or strain, and chronic knee pain. Other possible causes, such as injury to the knee, are more rare. Osteoarthritis 22. Sprain or strain 17. Chronic knee pain 15. Knee ligament or meniscus tear 8. Fracture of the leg 4. Bursitis 2.
If you experience sudden attacks of severe knee pain and your knee also becomes red and hot, the cause is likely to be gout, which is a type of arthritis. Gout is caused by a build-up of uric acid (a waste product) in the body, which can form crystals in the joints. These crystals cause the joints to become inflamed and painful. Gout will cause severe pain in the knee and limit movement of the joint. You may feel pain even when you're resting, including at night.