Psoriatic Arthritis - very little swelling?

Hi everyone, I'm 25 and from Scotland, living in London for the past 4 years and have recently been referred to the rheumatologist for suspected psoriatic arthritis. I've had psoriasis since I was very young and since I was a teenager I've has issues with the knuckles on my hands but never any other joint problems. I'm a keen runner and about a year ago started to develop knee pain which we thought was just runners knee so I wasn't too concerned, but doctors and physio's have since done some bloods and family history and now believe I'm likely to have psoriatic arthritis. The rheumatologist has scheduled a few scans to completely rule out any sort of injury but believes it is arthritis, we just need to wait on the scans coming back to be able to give me a formal diagnosis and look into treatments.

The only thing I'm finding a little strange at the moment is that my joints aren't very obviously swollen, which is also leading to a difficult diagnosis. I do find my fingers swollen, as I can't get jewellery on and off and when I have it on can see that they're swollen, but my knees which are more problematic don't swell up to a point that it's massively visible, even when I'm in a great deal of pain. Has anyone else ever had this? I know that swelling is a common symptom but it would be interesting to hear if others have had a diagnosis without lots of swelling!