Anything, or nothing, or something in between 😂 think that covers all bases!
If you believe dreams can be your mind’s attempt to process waking events during sleep then ask yourself what you think it means based on each element.
Dream is set in work - so possibly this is something work related - are you busy/stressed about work?
Slippy floor - might indicate something beyond your control or something temporary or a warning to be careful, or that its something simple like water but still vv messy.
Kneecaps shattering - loads of symbolism could be read in here (brought to knees, cut off at the knee, kneeling in a humbled way, or a NornIron connection
)
So maybe - “watch your step at work because an unexpected in-flow of something is about to make things dangerous and if you aren’t prepared you will be humbled in a very painful way” 
Luckily I’m not Mystic Meg so thats not a prediction just a guess. The best person to tell what it means isn’t me its you, you know what work means to you, what feeling out of control (slipping) means to you and how important your kneecaps are to you 😂
Symbolism can be shared between people groups, nations but really you need your own brain with your personal symbolism to think about what it might mean. Remembering too that it might be just a random assortment devoid of any deeper meaning - or any meaning at all.
And reading your post & typing ‘kneecaps’ so many times has made mine twinge a bit too so maybe thats the men/balls common wince thing.
But like thats a load of waffle from me - what do you think it means?