Wiberg classification is a system used to describe the shape of the patella based mainly on the asymmetry between the patellar medial and lateral facets on axial views of the patella. Increasing number type indicates a larger degree of asymmetry.

• Wiberg type 1 or a
  • roughly symmetrical facets
  • concave facets
  • equally sized facets
• Wiberg type 2 or b
  • slightly smaller size of the medial facet
  • concave aspect of the lateral facet
• Wiberg type 3 or c
  • markedly smaller size of the medial facet
  • more vertical orientation of the medial facet