John Furgerson III
Your knees will be fine as long as you wear some type of nice pads.
John, I know you mean well but that is such false bliss! Yes, knee pads will cushion your knees from some aches and pains in kneewalking and such. But pads and braces do NOTHING to prevent acute knee injury if you torque your knee, somebody falls on your knee, your foot catches in your hak and you land on your knee....
To the original poster: injuries happen in ALL physical activities, and accidents happen in all of life. Many aikido injuries are due to improper attention to proper posture, body use and safe body mechanics.