OBJECTIVE: This study investigates the clinical utility of infrared thermography in the detection of sympathetic dysautonomia in patients with patellofemoral pain syndrome. The patients exhibited anterior knee pain, radiographic evidence of patella alta and the clinical signs and symptoms of patellofemoral pain syndrome.

DESIGN: A case control study was carried out with two groups of patients: patients with anterior knee pain, and patients with no knee pain as a control

SETTING: Private practice.

PATIENTS: Group 1 consisted of 30 patients with patellofemoral pain syndrome. Group 2 consisted of 40 control patients with no history or presence of knee pain. Control patients were consecutively selected, and the knee pain patients were consecutively selected from a population-based sample.

OUTCOME MEASURE: Infrared thermography scans were obtained on the knee pain patients and control patients to determine the sensitivity and specificity of infrared thermography for detecting patellofemoral pain syndrome.

RESULTS: Twenty-nine of the 30 knee pain patients in group 1 had patellar thermal asymmetry from right to left sides (sensitivity 97%). Thirty-six of the 40 control patients exhibited thermal symmetry from right to left sides (specificity 90%). The incidence of patellar thermal asymmetry was found to be statistically significant when tested by chi 2 analysis (p less than .001).

CONCLUSION: Infrared thermography appears to be a useful, noninvasive diagnostic test in the diagnosis and management of patellofemoral pain syndrome. The high incidence of patellar thermal asymmetry and dysautonomia at the patella in patients with patellofemoral pain syndrome implicates somatosympathetic mediation in this disorder. This may be helpful in understanding the evolution of patellofemoral disorders.

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