Ball joints are spherical bearings connecting the control arms to the steering knuckles, allowing for suspension movement and steering articulation. Commonly used in both upper and lower control arms of independent suspension systems, they facilitate vertical and rotational movement while maintaining load-bearing capacity. Construction typically involves heat-treated steel forging with a hardened ball stud and a polymeric or metallic socket. Integral boots protect against contamination and maintain lubrication, and pre-loaded designs minimize play and enhance handling precision. Failure modes often include boot degradation leading to corrosion and excessive play, requiring replacement to maintain suspension geometry and steering control.