What is the role of imaging studies in the workup of patellofemoral syndrome (PFS)?

Updated: Sep 15, 2020
  • Author: Noel F So, MD, FAAPMR; Chief Editor: Consuelo T Lorenzo, MD  more...
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  • Imaging studies usually are not necessary in order for a physician to diagnose or recommend treatment for patellofemoral syndrome (PFS). Imaging studies should be considered for unusual presentations and for persons in whom the syndrome is refractory to conservative management.

    • Sunrise views should be included with anterior-posterior (AP) and lateral radiographic imaging of the knee. Limited positions of flexion are available for such viewing. These radiographs provide more of an indirect observation of what is happening within the articulation.

    • Lateral patellar tilt and a high-riding patella (patella alta) may be observed.

    • Osteophytes or joint space narrowing may be identified, suggesting arthritic changes in the articular cartilage. [6]

  • Nuclear scans are less likely to be of value in defining PFS and are more useful in helping to identify other, less common conditions that may mimic PFS, as outlined in the differential diagnoses. When changes have occurred in the retropatellar cartilage, mild increases in uptake of radionucleotide may be observed. Increased uptake of radionucleotide is not limited to the patella; it may be seen in the proximal tibia, distal femur, or patella. [7]

  • Computed tomography (CT) scanning and magnetic resonance imaging (MRI)

    • CT scanning and MRI allow for imaging at various angles of flexion.

    • CT scanning with the knee in full extension has been demonstrated to more accurately detect patellar subluxation.

    • Cross-sectional viewing allows more direct visualization of the articulation between the patella and femur.

    • Schutzer et al identified 3 patterns of malalignment using CT scanning [8] :

      • Type 1 includes patellar subluxation without tilt.

      • Type 2 is described as patellar subluxation with tilt.

      • Type 3 is patellar tilt without subluxation.

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