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.
A tumor in the soft tissue or bone of the knee joint can also cause pain in the back of the knee. In addition to discomfort, a tumor will likely include the appearance of a palpable mass, trouble. bending the knee and pain even when no weight is being placed on the legs.