What Causes Difficulty In Straightening And Bending Leg After An Injury?

I injured my leg 4 weeks ago in a jetski wipeout, but since I could walk and didn't feel a lot of pain, I figured I had just sprained my knee and bruised my foot. However, after 4 weeks, I still can't straighten or bend my leg to the limit and some swelling persists. I am currently unemployed and without health insurance, which is why I haven't had it examined. Is there a way to possibly identify structural damage without an MRI or xrays? Wouldn't I be in pain or even unable to walk if I had such damage?