I recently had severe stiffness, pain and swelling in my right leg after returning from a daily bike ride. The swelling lasted for a week and the stiffness and pain when climbing stairs and performing routine daily activities was unbearable. The lower part of my quad near the knee felt very loose and unstable and was extremely painful to the slightest touch. I could not lift my leg on its own as the pain was too much. After approximately 1 week and RICE the swelling went down, however the pain behind the knee cap shoots through from side to side from time to time. It may go away for a couple of hours and return for several. It is hard walking both up and down stairs as the sharp pain is underneath the kneecap. I have pain in the knee throughout the night which sometimes radiates down into the calf and front of the lower leg. I am awaiting the results of m MRI. Any idea what this may be.

Maybe your meniscus is ripped it may just need a quick fix with endoscopy. It is a good thing that you had an MRI done .