Wheel Problem
 

Hey guys , i have 87 rx7 and for the past couple of weeks , my left front wheel has been rocking back and forth inside the wheel well , it is not rocking on the stub axle , it seems to more pivot along the steering arm, like if the shock alowing it to swing in a pendulum like manner.
Now I was wondering what could cause this, i was told the lower ball joint could be the culprit, but is there anything else that could produce this problem, also when it became really bad i had to drive it home , i noticed when i was braking the car pulled severely to the left, so at first i thought it was something to do with my steering system, but anyway let me know what it could , thanks