Patella Fractures

Milton T.M. Little
Marschall B. Berkes
Dean G. Lorich

Bony Anatomy

  • The patella is a complex three-dimensional bone.
  • The anterior, nonarticular surface is shield shaped with distal taper at inferior pole.
  • The posterior (articular surface) is elliptical shaped with three facets with thickened cartilage (Fig. 22-1).

    • Lateral facet—largest facet, concave, and plateaus laterally
    • Medial facet—convex, smaller than lateral facet
    • Odd facet—most medial aspect of the patella

      • Central articular ridge separates lateral and medial facet.

  • The blood supply is provided by dorsal vessels and also ascending vessels via the fat pad inferomedially into nonarticular portions of patella.1
  • Critical soft tissue attachments:

    • All soft tissues attach at nonarticular portions of the patella.
    • Soft tissue attachments are critical to extensor mechanism function.
    • Patella tendon inserts at inferior pole of the patella and can be affected by inferior pole comminution, leading to unrecognized displacement and extensor mechanism incompetence if not treated appropriately.
    • Quadriceps tendon inserts at superior pole of the patella.
    • Lateral retinaculum and medial retinaculum (including medial patellofemoral ligament) insert along the respective medial and lateral portions of the patella and frequently disrupted in patella fractures.


Figure 22-1 Bony anatomy of patella.

Radiographic Anatomy

Radiographic views2

  • True lateral of the patella: obtained with limb in neutral rotation (Fig. 22-2)

    • Salient features

      • Articular tangent; correlates with articular ridge between medial and lateral facets
      • Secondary articular density; created by confluence of edge of the lateral facet with variable contributions from the edge of the medial facet or intersection of the medial and odd facet
      • Anterior cortical density

  • Accessory view of the lateral facet: obtained with patella in approximately 20 degrees (range 12 to 35 degrees) of external rotation (Fig. 22-3)

    • Salient features

      • Tangent to the lateral facet.
      • Best view to visualize displacement at the lateral facet articular surface.
      • Articular surface will appear as a straight line.
      • Proximal beaking visualized.

  • Accessory view of the medial facet: obtained with patella in approximately 30 degrees (range 15 to 45 degrees) of internal rotation (Fig. 22-4)

    • Salient features

      • Tangent to the medial facet
      • Best view to visualize displacement at the medial facet articular surface
      • Hexagonal or sail shape


Figure 22-2 A and B:True lateral view of the patella.


Figure 22-3 A and B:Accessory view of lateral facet.


Figure 22-4 Accessory view of medical facet.

Preoperative Imaging

AP and lateral views of the knee are usually adequate to determine if surgical or nonsurgical treatment is indicated (Fig. 22-5).



Figure 22-5 A and B: AP and lateral views of the patella.

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Mar 25, 2020 | Posted by in ORTHOPEDIC | Comments Off on Patella Fractures
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