Patellofemoral Joint Syndromes Workup

Updated: Oct 21, 2015
  • Author: Jane T Servi, MD; Chief Editor: Craig C Young, MD  more...
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Workup

Laboratory Studies

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  • Laboratory studies are not indicated for patellofemoral joint syndromes, unless there is a need to rule out other potential causes, such as systemic, inflammatory, or metabolic disease.

    • Erythrocyte sedimentation rate (ESR) is elevated in an inflammatory process.

    • Liver and renal function may be abnormal in metabolic disease.

    • Antibody tests are elevated for rheumatoid arthritis or ankylosing spondylitis.

    • Knee aspirates show an elevated white blood cell (WBC) count in an inflammatory process, an abnormal Gram stain and culture in infection, and crystals when crystal arthropathy is present.

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Imaging Studies

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  • Radiographic imaging is not necessary to make the diagnosis of patellofemoral joint syndrome, but these studies can be helpful to the physician when excluding other potential causes (see Differentials and Other Problems to Be Considered). Particular findings can support the diagnosis, including the following:

    • Lateral plain films show the presence of patella alta or patella baja.

    • A sunrise or Merchant's view reveals lateral tilt and the relative height of the femoral condyles.

    • Magnetic resonance imaging (MRI), computed tomography (CT) scanning, and bone scanning are not needed in the evaluation of patellofemoral joint syndromes, but these imaging modalities may be used to evaluate other pathologic conditions of the knee if the diagnosis is in doubt. Dynamic CT scanning, 0-120 º, is useful in assessing patellar tracking in recalcitrant cases in which surgery is being considered. This study can be used in the rare patient who is suspected of having a patellar tilt or subluxation but whose radiographs are normal.

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Other Tests

A study reported that the use of surface electromyography signals (B2-frequency band of 45-96 Hz) of the vastus lateralis and vastus medialis muscles with referred anterior knee pain can provide diagnostic accuracy of patellofemoral pain syndrome. [12]

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