Might try step-ups (not to be confused with one legged squats) which for some people find are not as harsh on the knees. Probably around parallel level, if that suits your needs. Do use knee wraps/supports or a heat drawing lotion/gell may help, for you want a good blood supply to the area.
Lunges, though good, can be a balance problem, keeping in a straight line and over stepping for older gentlemen (even a lot of younger guy's I have noticed). Consider some very light, high rep, sitting leg extensions just to warm-up the area. This with some sort of ham string stretch. If going to squatting later, than box squats may be better for you. Setting the height to around the parallel range.
BB Hack squats can affect the knee joints a little different than regular squatting. Because with regular squatting the weight (bar) is on the shoulders, above the center of the body. With Hacks, the force is below the body. Quite a different dynamic for a lot of men. Another advantage is you can drop the bar a short distance if having trouble with the lift. With the bar on the shoulders, there could be more potential trouble with it. Good Luck.