1.Dislocations and Fractures
If your knee hurts intensely after a bump, bang, or fall, you may have broken one of the bones that meet up there — the thigh, shin, and kneecap — or shifted one out of place. Go to the emergency room or see a doctor as soon as possible. Sometimes fractures happen more slowly, causing tiny cracks at the ends of the leg bones. This can happen when you’ve started using your knee more.
2.Torn Anterior Cruciate Ligament
You hear a pop and can’t move after you suddenly change direction — often while playing soccer, football, or basketball. You may have torn your ACL, which connects the femur and the tibia and prevents the tibia from moving too far forward. Your knee will hurt and swell and feel unstable.