my knees are bad from dirt bike days in the '70s. Over the years I have collected 11 broken knees. I wear custom molded braces, daily, that you can hardly see under my blue jeans.
Issues I have with knees range from lifting and pulling a sled from a stuck, or simply unloading from a trailer, to when you turn out from a climb and the sled tries to roll downhill. By instinct, you put out a foot to supprt the sled from going over while throttling up to save the sled from going over and save it. Yeah, even hanging off the up side board during turn-outs smacking something weather it be a hard snow drift or rocks and stumps under the snow, I've been pitched to the down-side of the sled and twisted a knee trying to save it. Heck, I've blown a knee out walking over to the evergreens to take a leak. Breaking through surface crust and twisting a knee out of place as the foot comes back out of the crusty surface.
Sure glad there are bone specialists in the medical field.
I told my wife my initials (GAP) stand for my knee brace assistance
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----- Gimpster -----