As a runner I wouldn't say knees are particularly fragile, my knees can take a lot of beating, more than my shins, ankles or feet. Additionally the body operate

As a runner I wouldn't say knees are particularly fragile, my knees can take a lot of beating, more than my shins, ankles or feet. Additionally the body operates on use it or lose it so to maintain healthy knees you need to either walk long distances (e.g. hiking) or run.