I wouldn't scratch squats just yet. Try squating with a smith machine or a hack squat to see if you can get the leg pump you want. I've got a neck injury that makes it difficult to put the bar on my back, but I've been lucky enough to find a hack squat machine that can be modified for front squats and it works beautifully.
If you have nothing else, work some lunges with dumbbells, and they would still help. Superset them with wall-squats, and you'll really feel it too.
Remember - "No pain, no gain" is a myth!