CV joints, boots (gaiters) and driveshafts are a common MOT failure. All drive-shafts and prop-shafts have a flexible joint at either end which needs continuous lubrication. These joints (CV joints) have a rubber boot to hold the grease within the joint itself. These split over time and allow the grease to escape. This is an MOT failure due to grease escaping causing premature wear of the CV joints, and in some cases, can spray grease onto your vehicle brake components.
Common MOT Failures
Ben Grave, Mark Lawson