OK... KNee pads... Bit of my forte as it were. In the late 80's a was skating and competing on vert ramps. Back in the day we wore 3 layers of padding on our knees. 1stly a neoprene "gasket" which stopped pads from slipping off, followed by a pair of traditional large plastic capped skate style knee pads (with the plastic cap removed usually because nothing was left from previous wear/falls etc...), then the outer pad - a large plastic-capped knee pad which also included some shin protection ...
OK... KNee pads... Bit of my forte as it were. In the late 80's a was skating and competing on vert ramps. Back in the day we wore 3 layers of padding on our knees. 1stly a neoprene "gasket" which stopped pads from slipping off, followed by a pair of traditional large plastic capped skate style knee pads (with the plastic cap removed usually because nothing was left from previous wear/falls etc...), then the outer pad - a large plastic-capped knee pad which also included some shin protection.
Snowboarding doesn't really require this level of protection. But as I had this built-in defence mechanism of using my knees as the first line of impact in a fall, my knees started taking a hammering. I initially bought a set of pads that were fairly plyable, soft and comfortable thinking they would do the job. Unfortunately not. They got pulled off the knee fairly easily and didn't offer the level of protection in an impact as required.
I was tempted to use a set of my MTB knee pads under the trousers, but knew in a fall, the trousers would rip through fairly quickly. Same with skate pads - the plastic will easily allow the fabric to tear through if worn under trousers. And you'll look like a right tool if you wore them over! lol!
So I eventually settled on a pair of these Demon knee pads - they're fairly think and can withstand a fairly serious impact without damaging clothing. They're also designed to allow normal knee movement so are nice and comfortable. Definitely can't go wrong (and not a bad price either - I paid 3 or 4 times that a few years ago!)- http://www.absolute-snow.co.uk/V/Demon_SNOWBOARD_Knee_Pads_Extra_Large-(13543)
Although if you think about it, you will possibly be travelling faster/higher on a snowboard or skis than playing volley ball etc... The level of impact can be far greater. I still reckon the indoor court pads are far too soft. But if you're not being too adventurous, then they could possibly work.
Some sound advice there Garrick, now it makes sense why i keep putting holes in my pants knees as i wear my plastic capped skate pads, ill give the Demon ones a go this season. Although a couple of years ago they saved my knee cap when i landed on a rock and took a deep gouge out the plastic cap. Paul.
Have a look for Burton Red Basic kneepads, quite slimline and stretchy. Should be around £15. Might just do the trick and will certainly fit under your trollies without causing any damage!