Instead of loading, try twisting your torso into the swing, to save your knees.
I use a very strong SW, racket closer to flat on the ground than up on edge in ready position. SW is fine, just moderate your backswing and hit flatter than you currently do.
I'm 64, have broken my legs 3 times, 2 needing multiple pins, wire, and plate. Broken my two collarbones twice each, separated both shoulders more than twice, and one bad dislocate that still haunts my rightie serve (lucky for me, I'm lefty). When it's cloudy and almost raining, I'll often switch to conti for every shot, to save the shoulders. That would be like one day out of 50 tennis days.