Establishing a "healthy" body weight

[Entity]

After three long years of being away from my favorite competitive sport to play (Ultimate Frisbee), I've started training seriously to try to get back on the field again. A few years back inadequate training led to a series of hamstring and knee injuries mostly sustained while playing in tournaments (playing 4-8 hours per day for 3 days sustained takes a toll quickly). Now I'm trying (link to running thread) to get back into top shape. I'm concerned about the overall health of my knees as degenerative disorders may run in my family (both my dad and my uncle have had multiple knee surgeries, but this may stem from working as loggers for 20+ years of their lives).

As much as I've got general fitness goals, like sustained mile times, distance runs without dying, etc., I'd also like to be the appropriate weight for my body. Unfortunately, I have absolutely no clue what range I should weigh. I'm 6' tall and currently weigh somewhere around 205-210lb. Last I checked it was 205.5, but I don't consider that highly accurate as it wasn't much of a baseline, just a single measurement done in the morning.

Obviously if I go by the BMI scale I'm overweight. I don't dispute that at all. But according to BMI calculations, I can't remember the last time I was actually sub-25. Around 18 years old in high school would be my guess, but that was before my musculature was developed, etc. Even when I was going through extreme physical stress, hiking the Pacific Crest Trail from Mexico to Canada in 2001, I generally hovered around 188-190lb, and I was burning well over 7000calories/day (our average was ~27mi/day for a 3+month stretch). I've had various "phases" including weightlifting, long distance hiking, etc., and different bodytypes have come along with the training necessary for those.

Basically what I'm trying to do is ensure that I'm not putting my knees and joints through more stress than they should endure -- and that I'm at a very healthy weight -- but I have no real idea how to best establish a healthy baseline. Body Fat Testing via immersion? Guesstimates based on BMI? I'm not looking to spend a ton in the process of finding this out, but since I am aiming to be involved in a very competitive sport and it's going to stress my body a fair amount, I'd like to have an idea of what to shoot for, before the big training begins.

I know, I know. tl;dr. Any comments for anyone who has made it this far?

Rob