What Causes Severe Knee Pain After Working Out?

HI Doctor,
I have been working out my legs 4 weeks ago. I was doing leg press. I took the most of weight in my knee. But just had the little pain in the beginning. Later for next 2 weeks i was doing eliptical and cycling. I think this has worsened the knee further. Now i have more pain in my knee which harms me while walking. Can u tell me is this something due to ligament tear.