First, Warm Up Your Hammies
The hamstrings are big knee stabilizers that don't get enough credit since it's the quads that are directly attached to the kneecap, not the hammies.
We're constantly thinking about the muscles on the front of the thigh and don't realize that healthy and strong antagonists can create more range of motion, more stability, and make the reps you do of a given compound exercise much smoother.
Squats Come Second
Whether you're injured or not, "breaking the rules" and putting squats second in line after a few sets of hamstring curls, reverse hypers, or horizontal back extensions can do your lower body good.
You don't have to go heavy either. The goal is to get plenty of blood flow back there, so chasing a pump via higher reps and moderate-to-low weight would be the smart route.
John Meadows talks about healthy lifters pre-exhausting hamstrings before squatting for basically the same reasons, namely sturdier bottom positions for the squat and a welcome change to quad dominance.