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.
giving out or weakness of the knees can have different causes. These can include problems outside the knee joint itself (weak muscles for example) or inside the knee (torn ligaments or cartilage). See an orthopaedic surgeon to address your individual problem.