Finished SSLP - quad problem - please advise

I am a 48 year old male. I began SS in March and I believe my linear progression is now complete. Squat 300, Deadlift 345, Bench 205, Press 135

I am ready to move on to a new program, but need some advice because I have a problem I need to solve first.

One of the key motivators for me is to avoid some of the problems my father and grandfather had. My grandfather was in a wheel chair his last 5 years of life due to lack of leg strength. My dad also has weak legs and has had both knees replaced. I myself have had multiple meniscus tears/surgeries, and before SS, I had skinny legs like them.

Here is my problem: Lately, even though I am stronger, my quads are constantly sore/weak. Hamstrings, Glutes, Erectors are all fine. Until recently I kept thinking the sore quads issue was just a phase to get over via training, but then I injured my right quad Monday on my third set of squats.

When I begin a new intermediate training program (after quad injury heals), I have strength goals, but more important, I want to overcome this issue with my quads so that I can walk up stairs, get out of my car, get off the pot without being weak and sore.

Can you please provide some advice, or point me to a program that might allow me to continue my strength gaining journey and “fix” my quads?

Thanks