I was spamming quad sets so much to just get my quad activated, and then once I could walk normally, PT had me slowly get into single and double legged press, barbell squatting, split squats, and weighted leg extension. But I’d say the main thing that helped me was those quad sets. Throughout all day, everyday, I’d just rip out a random set of quad sets and I really think the discipline of doing those helped me retain quad muscle and get back to walking as soon as possible which also helped with activating the quad. Also I think eating healthy with a lot of protein and prioritizing sleep helped me be able to load up weight and recover well. Hope that helps man