Welcome to healthcareMagic. Knee pain
with swelling commonly indicates a cyst, a Bakers cyst, so to say.It could be bursitis, tendinitis
.Then there are arthritis
of different origin like... rheumatoid, psoriatic, gouty, seronegative type. You might have had a meniscus
injury also. So pl pay a visit to an orthopedician and get a X-ray / MRI(if required). Meanwhile, give your affected limb rest and may take some over the counter analgesics for pain relief.Get well soon.