Patella alta

	Because the underlying trochlear groove is flatter at its upper end, it is easier for the patella to subluxate or dislocate when the knee is in extension (straight).
High-riding patella (patella alta) subluxing to the outer (lateral) side during knee extension.

Cause of patella alta

Patients with primary patella alta are generally born that way. It may cause no problem, or they may suffer from anterior knee pain and/or patellar instability. In cases of rupture or avulsion of the patellar tendon, the quads muscle may pull the patella into an abnormally high position.