q-angle
Increased Q-Angle
 
The Q-angle is an estimate of the effective angle at which the quadriceps averages its pull. It is determined by drawing a line from the Anterior Superior Iliac Spine (bump above and in front of your hip joint) to the center of your knee cap and a second line from the center of your knee cap to the insertion of the patellar tendon (where the tendon below your knee cap inserts). Normal is below 12 degrees, definitely abnormal is above 15 degrees. Many times adding to the strong lateral pull of the bulk of the quadriceps is a weak vastus medialis. This is the portion of the quadriceps that helps medially stabilize the patella. It runs along the inside portion of the thigh bone to join at the knee cap with the other three muscles making up the quadriceps. Some of the mechanical conditions that may contribute to this include:
 
See also Chondromalacia Patella.