Three days ago I was doing squats, without feeling any unnatural pain. On the morning after, I couldn't extend my leg without pain in the lower, lateral part of my left knee, and flexion upon internal rotation hurt as well. There was no swelling or heat, however. Day two, I only felt pain when beginning movement after having the knee in a fixed position for a long time, and this quickly disappeared after a few steps or kicks. Day three, even this is gone, and the only pain left is a light pain when trying to hyperextend the knee. Days two and three, I haven't had any problems running.
Any ideas on what this could be (obviously getting an MRI would give the answer, but I haven't yet got an appointment)? The pain localisation and stiffness on the first two days points towards a torn meniscus, but the absence of trauma and the quick recovery seem strange. Has anyone heard of similar symptoms? Are there any potential problems in returning to weight training and contact sports?