Some people by virtue of their own build and anatomy are more prone to dislocate their kneecap.
Shaun Livingston must be one of those people.
In his rookie season, two years ago, Shaun missed 39 games when he dislocated his RIGHT kneecap.
Last night he dislocated his left kneecap.
I have a little medical background, so I will add a comment.
The kneecap (patella) rides up and down in a trough or shallow rut formed by both the bone in the thigh (femur) and the bones in the lower leg (tibia and fibula).
The patella is embedded into the quads tendon.
For the kneecap to be dislocated, it has to ride up and over the ridge of the trough that it sets in and in the process of dislocating, the quads tendon often is injured or tears and the cartilege that surrounds it often is injured.
Recovery is almost certain, but takes at least 6 weeks for the bone, cartilege, and tendon to repair.
It has already been said that Shaun may be done for this season.
The Clippers are battling for a playoff spot, and right now are tied in losses for the 8th and final West playoff spot.
Here are a couple articles about dislocation of the patella.
http://www.athleticadvisor.com/Injuries/LE/Knee/Patella/patella_dislocations.htm
http://hcd2.bupa.co.uk/fact_sheets/html/Dislocated_kneecap.html