I fell about 3 weeks ago cracking my sternum and injuring my right knee. My sternum hurt the most so I paid little attention to my knee. As the pain in my knee increased My doctor gave me a shot of cortisone in my knee which really did not help. Today, 1 week later the pain is unreal. My knee throbs when standing, severe pain pain when straightening my knee, pain when bending. Severe pain going up and down stairs. What do you think I have done to my knee. Thank-you