4 months ago I hit my knee on a glass shelf .i thought that I would just get a bruise and that would be it but since then I have had knee pain .it ranges from just painfull when I walk to can t hardly move it at all and no strength in it to lift it and more painfull when I try to bend it and put pressure on it like walking up stairs.it also gives way sometimes. I ve been to the doctors and had an Mri but they say even though something looks odd on the scan they can t tell what it is. Also a week ago I fell on my knee which has now made it worse and I ve got a knee brace on and on crutches until I can get an appointment with an orthopaedic surgeon . Any ideas what could be wrong.