Pitting is not a failure...leaking grease or oil is :-s
If you have oil in them & they are leaking try draining out & replacing with CV grease (one shot packs).
You can drain down the swivels before MOT, so they don't leak, clean the area, get it MOT'd & replace the swivels at your leisure...don't forget to put something back into swivel housing if not doing job straight away :roll: