Knee soreness?

Been in the gym for about 4 months and change. I used to hit legs once every 7 days, about little over a month and half ago i started hitting them every 5 days(muscles were sore less and had the time). Past 2 weeks my muscles havent felt sore for long but my knees feel sore(or mildly painful) when i squat or lunge with no weight. No muscle soreness just knees itself. If i do multiple squats or lunges the pain goes away for a day or two then comes back.

Knees dont hurt when walking or bending or anything else. Just full ROM lunge or squatting motion.