Right, well, I'm a rugby player, but I've had a bad knee injury, so I've been out of the game for a few months. I'm just getting back into training now. The problem is, most of my teammates and competitors have a headstart on me. So, what I'd like to know is what is the most effective way to quickly and safely gain strength in my arms, chest, core, and most importantly, legs? I'm not concerned about having good definition or huge arms or whatever, my sole focus is maximizing strength.
Mayhem and ThePurpleOrange covered it well,but please first and foremost that you get your knee sorted, a heavy strength training programme with a knee injury is a recipe for disaster.
Squatting heavy with a knee injury may lead to a worse knee injury and cause you never to play rugby again.