what causes the front wheels to lean in at ? on 1992 Mercury Sable

the front wheels are leaning at the top and it wearing out the inside of the tires.

Asked by for the 1992 Mercury Sable
2 answers
This is usually a suspension issue which causes an alignment problem. Usual suspects are: worn ball joints, worn out struts need to inspect to find out which. Betting on the worn out ball joints.
agree with bak it could be several items but alignment will let you know what is bad