Driver was returning home from a pre-season safety meeting. Traffic was heavy at the end of the long weekend. The drive had slowed to stay with the flow of traffic.  As the vehicle entered a left hand curve the right front lower ball joint sheared causing the front end to drop and the driver to momentarily lose control of the vehicle. It went into a skid briefly crossing the double solid center line then went off the road on the right narrowly missing the end of a no-post guard rail and ended up in the entrance to a private driveway. No injuries occurred. Speed at the time of the failure was 80 kph. Damage was $1300.  If the driver had been going much faster the accident would have been very serious.  The vehicle is a 2003 Ford F-150 4x4 with 311,000 kms. The vehicle had been serviced recently (<100km) but there is no record of a detailed inspection being conducted. Normally and end to end inspection is requested with each oil change. There is no agreement between various mechanics consulted on whether an inspection would have caught this potential failure.