Suspension Ball Joint

WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

Jack up the vehicle until front tires are off ground.
Grasp the bottom of tire and move it in and out in axial direction. If relative movement (B) is observed between the brake disc cover (A) and end of front arm (D), ball joint (C) may be excessively worn.

Fig 1: Relative Movement Between Brake Disc Cover And End Of Front Arm
Courtesy of SUBARU OF AMERICA, INC.
Grasp the end of front arm and move it up and down. If relative movement (A) is observed between the housing (D) and front arm (C) boss, ball joint (B) may be excessively worn.

Fig 2: Relative Movement Between Housing And Front Arm Boss
Courtesy of SUBARU OF AMERICA, INC.
If the relative movement is observed in the preceding two steps, remove and inspect the ball joint. If the free play exceeds standard value, replace the ball joint. < Ref. to FRONT BALL JOINT . >
Damage of dust cover
Visually inspect the ball joint dust cover. If it is damaged, remove the front arm. < Ref. to FRONT ARM . > Measure the play of the ball joint. < Ref. to FRONT BALL JOINT . >
1. If the free play exceeds standard value, replace the ball joint.
2. If the dust cover is damaged, replace with a new ball joint.
  NOTE: When the front arm ball joint has been removed or replaced, check the toe of front wheel. If the front wheel toe is outside the specified range, < Ref. to WHEEL ALIGNMENT . > adjust toe-in.
  
  Fig 3: Dust Cover
  Courtesy of SUBARU OF AMERICA, INC.