How your body is formed. The patellar tendon connects the bottom
edge of the patella to the front of the shinbone. When the patellar tendon is very long, the patella can slide too high on the knee joint. Other physical
traits that increase your risk of having knee problems include a patellar
shape that is unusually small or flat, flat feet, hips set more to the outside
of the knees than usual, a shallow femoral groove for the patella to glide
along, or a knock-knee position.
imbalance in the contraction of the thigh muscles. Your quadriceps are a group
of four muscles. If the outer muscle is stronger than the inner muscle, or if
it tends to contract quicker than the inner muscle, your kneecap can be pulled
toward the outside as your leg straightens.
Tendons and muscles in
the leg, foot, or hip areas that are too tight or too loose. For example, weak
quadriceps combined with tight
hamstrings and a tight
iliotibial (IT) band can pull the patella toward the
outside of the knee.
A blow to the kneecap, causing it to shift
(partially dislocate or sublux) or
dislocate. Dislocation can also be caused by twisting
the thigh inward while the foot is firmly planted, pointing outward. After an
initial dislocation, the patella is at increased risk of dislocating more
A previous injury that has healed improperly, causing an
imbalance in how the leg functions.
Generalized ligamentous laxity,
or "loose-jointedness." Joint instability results from ligaments that are not
as tight as they should be.