Patella alta

Patella alta, or a high riding patella, describes a situation where the position of the patella is considered high. It may be idiopathic or may result secondary to a patellar tendon rupture. 

Epidemiology

Associations

Several conditions are known to be associated with patella alta, including:

• idiopathic retropatellar pain ⁵
• recurrent dislocation of the patella ²
• chondromalacia patellae ²
• knee joint effusion ²

Patella alta may also occur as a result of spastic cerebral palsy ⁶.

Radiographic features

On sagittal images, it is usually considered when the Insall-Salvati ratio is greater than 1.3-1.5 ^1-3.

On radiography, it is important that standard positioning is used, with the knee flexed at 30 degrees. An off-angle x-ray beam or non-standard positioning may result in a spuriously abnormal ratio.