Hello,
Thanks for the query to H.C.M. Forum.
Your complaint is pain in knee ( one or both , not mentioned inn query).
Due to excruciating it is natural that patient develops stomach pain,
vomiting.
If pain in knee is due to infection patient will also suffer from chest cramps and pain all over body.
Since you mentioned that there is swelling and patient is unable to walk, so reasons may be as,
Osteoarthritis,
rheumatoid arthritis,
ligament rupture of knee joint due to sudden jolt,
traumatic swelling and hence pain ,
gout ,
post
fever (
dengue, Chicken guinea ) arthritis.
So please consult a physician / orthopaqedician and get in complete treatment after examination ( physical and serological ).
Hope I have answered your question .
If further any question I will reply.
Good luck for speedy recovery.
Dr. HET