What an exercises can I do??

Today is 3 weeks post partial meniscetomy of posterior body into medial meniscus. I am dying to get back to doing my ab workouts(which all involve using my legs) and I don’t know what is safe to do.. am I able to do planks? I tried straight leg raises and I don’t know if it’s too much stress on the healing knee or not. Didn’t feel bad while doing it but a couple days later my quad felt super tight. I won’t start PT until next week and by then I’ll be at 4 weeks. I’m not sure what I should be doing or shouldn’t be.. I’ve been focusing on range of motion. Heel slides and knee flexion and extension without any weight. I’ve been foam rolling and using the massage gun I’m still tight and stiff though. I hope the ab exercises I tried for a couple days weren’t too much stress on the knee. I’m not going to do them anymore but curious if anyone knows what I can do?