Distribution of substance-P nerve fibers in the knee joint in patients with anterior knee pain syndrome

Abstract

The etiology of pain in anterior knee pain syndrome is a matter of controversy. The normal, articular cartilage is aneural, so defects in the surface are not thought to produce pain. Some authors have sought the origin of the pain in soft tissue structures around the knee. Knowledge of the distribution of nociceptive nerve fibers around the knee would provide insight for treating anterior knee pain syndrome. Twenty consecutive patients (28 knees), all women, with anterior knee pain syndrome (group I) participated in the study. For comparison we used two groups of patients: 20 patients with an osteoarthritic knee (group II) and 20 patients with anterior cruciate ligament rupture or meniscal lesion with no history of pain in the anterior compartment (group III). Immunohistochemical techniques using a monoclonal antibody to substance-P (SP) were employed to identify nociceptive fibers. For statistical analyses we used the one-way ANOVA test, which was corrected with the LSD test, at the level of significance P < 0.05. Results of the study demonstrate that SP-immunoreactive nerve fibers are widespread within the soft tissues around the knee. These tissues include the retinaculum, synovium, fat pad and, in some circumstances, bone. In cases of anterior knee pain, the presence of neuropeptide-containing fibers was statistically significant in the medial retinaculum (P < 0.005) and in the fat pad (P < 0.001) compared to group III, and compared to group II (P < 0.05 and P < 0.007, respectively). For lateral retinaculum this relationship was not so statistically strong (P < 0.02) and was equal in comparison between anterior knee pain patients (group I) and group II or group III. There were no statistically significant differences in the distribution of substance-P nerve fibers in the fat pad, lateral and medial retinaculum or synovium between groups II and III. The results of this study provide immunohistochemical evidence suggesting that pain may originate in the fat pad and medial retinaculum of many patients with anterior knee pain syndrome.

Patellofemoral pain: an update on diagnostic and treatment options

“…Free nerve endings are found in the patellar tendon, retinacular tissues, pes anserinus, synovial tissues, and the fat pad [13], Dye [14] performed knee arthroscopy without anesthesia and found that the most highly sensitive structures were the fat pad and synovial tissues whereas the articular surfaces, menisci, and ligaments were much less sensitive. In patients with anterior knee pain, the fat pad and medial retinaculum have a higher concentration of pain receptors than in controls [15]. Articular cartilage is not innervated, but subchondral bone is richly innervated and can be painful when palpated.…”

The nature of anterior knee pain following injection of hypertonic saline into the infrapatellar fat pad

“…The evoked pain was severe and could be accurately localised. Nerve fibres that are sensitive to substance-P (a peptide that activates nociceptors) have been found in the fat pad and are more prevalent in those with anterior knee pain compared with patients undergoing anterior cruciate ligament surgery or with knee joint osteoarthritis [20,21]. Surgical excision and injection of local anaesthetic and/or steroid into the fat pad have been reported to alleviate pain in some cases of anterior knee pain [3,4,19].…”

Hypothesis: Anterior knee pain in the young patient-what causes the pain?"Neural model"

“…It is well-known that pain in patients with PFM can not be ascribed to a single factor, but to several. The infrapatellar fat pad, subchondral bone, the quadriceps tendon, patellar ligament, synovium, the medial and lateral retinaculum all have a rich nerve supply and these structures, individually or in combination, may cause pain (Fulkerson 1983, Fulkerson et al 1985, Wojtys et al 1990, Dye et al 1998, Witonski and Wagrowska-Danielewicz, 1999, Sanchis-Alfonso et al 1999, Biedert and Sanchis-Alfonso 2002.…”