I have the same problem, did you injure your knee? - My knee also clicks when going from full straight to partially bent. Mine came from a few injuries to the knee - My doctors just keep telling me to take advil and take it easy. After months of that with no real improvement; I started becoming more active - my symptoms started to worsen and I requested another doctor. After going to a specialist and having an MRI done, I was sent to physical therapy with a "stretched ACL, possible torn meniscus, and irritated MCL". Now after 6 weeks I have improved but not to the point where I can do my everyday routine comfortably - I am wondering if it is Chondromalacia patella??? I was told that if it is, it might require scoping and cleaning or smoothing of the backside of the kneecap. Good luck.