Luxating patella.

hello....my boston terrier(chelsea) just turned 12 months...for the past week i notice that she lifts her left back leg and can't walk on it....i gently felt it to see if there is any muscle cramp or joint dislocation...although i am not an expert i didn't feel anything, so what i did is gently moved her leg, just like stretching...then i felt a slight 'click' as if here joint 'popped' back into place...this has happened several times the last week(it occurs randomly during walks, once when going up stairs)...my stretching technique has worked every time and i am able to 'pop' her leg back into place and she walks fine after that....when i 'pop' it into place she does not seem to be in any pain....i started giving her 'joint rescue' containing glucosamine, msm, sea cucumber and chondroitin...she is not overweight and i usually give her chicken breast, or cook some vegetables with meat for her (no canned food since i have had her, which is about 7 months) i just lost my job and really cannot afford a vet...if it was an emergency i would of course take her to the vet, but i am trying to exhaust all other options....please help me by telling me what you think it is, and what you think i should do whether it consists of visiting the vet, exercise, diet etc,,,thank you for reading my issue