If your knees really bother you, try wearing a pair of the new carbon fiber Asterisk motox knee braces like I do, and have for years.
They are ergonomic(made to fit the rt and lft leg), and offer substantial chainsaw protection, light weight, and expensive as hell! 700 bucks.
They give me an added degree of stability and protection that I would feel very vulnerable and naked without.
I can stuff my foot, shin, or knee into a jagged vee crotch, I kick and pop old dead stubs off on my way up with my knee, it's kind of a feeling of lower limbed indestructability. I wish I could have that same degree of upper limbed power, stability and protection.
Any of you old pros ever try wearing the velcro 3 piece bull riding vests doing nasty jagged takedowns? I like em.
I had a complete ACL replacement surgery on my right knee bout 18-20 years ago after a nasty motox crash, and I wore a brace of one type or another on that rt leg for years before it finally occurred to me to balance things out and wear two.
It's worked well for me, particularly with the new light weight high quality braces now available.
Work safe
jomoco