The doctor poked my knee a bit while I talked profusely about my ailment. He prescribed me some anti-inflammatories and instructed me to book myself in for an X-ray. He then spent 5 minutes complaining about computers and the digitising of medical records. Apparently, when a patient switches doctor's surgery, their records aren't transfered digitally, they're just printed off onto a stack of paper that no-one ever reads. So the overall Doc's conclusion was: a) things were better in the old days, and b) I don't know what's wrong with your knee.
X-ray tomorrow morning. No running for a bit, it seems. Swimming, maybe.