Is there any chance you have sciatica? Pain going down the leg and on the outside of the knee (as long as it's not in the knee joint), sound like symptoms I have when sciatica is flaring. Check out a dermatome map and see if the areas where you are feeling pain correspond to one of the lumbar distributions. L4, L5, S1 would be likely suspects for pinched nerves that could cause some sciatica symptoms.

DX: Psoriatic Arthritis, Osteoporosis, Psoriasis
Meds: MTX since Oct 2009, 15mg/week. Cimzia-restarted after 2 yrs away.
Epidural Steroid Injections x8; Lumbar Radiofreq Ablation x2
SIJ Steroid Injection x3; Bilateral Radiofreq Ablation SIJ x9