I love that your not letting your knees hold you back! I encourage you to train by walking up and down hills. This will help improve your strength and stamina while also increasing your stride length.
You might also think about using trekking poles. I've found that trekking poles give me a better walking posture which helps me to walk with less impact on my ankles, knees, and hips. This also will helps with your stamina and recovery!
Here's to a new PR!