Computerized thermography was used to evaluate 17 patients diagnosed with patellar tendinitis. The intent of this study was to determine if a specific patellar tendinitis thermal pattern could be distinguished using infrared thermography. A specific thermal abnormality was found over the patellar tendon in 14 subjects (78%). Twelve subjects showed focal "hot" spots, while two showed focal "cold" spots. The thermal abnormalities appeared as specific focal areas directly overlaying the patellar tendon, without disruption to the thermal pattern of the remaining peripatellar regions. The thermal gradient slope over the patellar tendon was greater in symptomatic knees. Five subjects returned 2-4 weeks later for follow-up thermographic examination. Among the follow-up subject group, changes in thermal asymmetry correlated with changes in symptoms 80% of the time. Computerized thermography appears useful as a noninvasive, objective method of detecting inflammation of the soft tissues about the patellar tendon, and also helps to differentiate this disorder from other knee pathologies. J Orthop Sports Phys Ther 1987;9(4):132-140.