Aims: The purpose of the study was to determine the distribution and speciþcation of nerve þbers in the infrapatellar fat pad especially concerning nociceptive substance-P þbres. Methods: The infrapatellar fat pad was taken as a fresh specimen out of 21 patients (4 male, 17 female, mean age 69 years) during total knee arthroplasty. It was dissected in þve deþned parts, þxed and embedded in parafþn. Immunohistochemical techniques using antibodies against S-100 protein and substance-P were employed to determine and specify the nerve þbres. Results: Studying all the detectable nerves present in 50 þelds (x200 objective) we found an average of 6,4 substance-P- (25%) of a total of 24,7 nerve þbres in the infrapatellar fat pad. There was a significantly (p< 0,01) higher number of substance-P-þbers (24,4 (28%) of 105,7) in the surfacing synovial tissue. The number of S-100-þbers was signiþcantly (p< 0,05) higher in the central and lateral part of the fat pad. Conclusions: The occurance and distribution of nerve þbres in the infrapatellar fat pad suggests a nociceptive function. A neurohistological role in the anterior knee pain syndrome is assumed.