Structural Changes, Not Neovascularization, Accounts For The Variation In Pain With Infrapatellar Tendinopathy

Abstract

The source of pain in patients experiencing chronic overuse tendinopathy is not completely understood. It has been proposed that vascular in-growth within the area of tendon degeneration is closely associated with an exaggerated nociceptive response. Changes to the sonographic appearance of the tendon are often reported with tendon disease; however, a detailed examination of the sonographic structure of tendon pathology as it relates to the onset of pain has not been performed. PURPOSE: To construct a statistical model that would account for the variation in pain scores reported by tendinopathy patients based on eight sonographic features. METHODS: Clinical and sonographic data were collected from 244 consultations of 51 patients receiving injections of hyperosmolar dextrose/lidocaine for their infrapatellar tendinopathy. Pain scores were documented using visual analog scales (VAS) for pain at rest, pain with activities of daily living, and pain during or immediately after sports. The following sonographic features were documented for all visits: hypoechogenicity, obvious intratendinous tears, occult intratendinous tears, injectant spread, neovascularity, intratendinous calcification, periostitis, and cortical irregularities. Each VAS item was entered into its own backward stepwise regression model (p ≥ 0.1 for exclusion) as the dependent variable with all eight sonographic features included as independent variables. RESULTS: The appearance of periostitis and both obvious and occult intratendinous tears explained a significant variation in the pain scores at rest (R2 =.14, F(3, 240) = 12.71, p <.001); periostitis, both obvious and occult intratendinous tears, and spread of injectant explained a significant variation of pain with activities of daily living (R2 =.08, F(4, 239) = 4.86, p <.01); and periostitis, and both obvious and occult intratendinous tears, spread of injectant and intratendinous calcification explained a significant amount of the variation of pain associated with sport (R2 =.09, F(5, 238) = 4.51, p <.01). CONCLUSIONS: The sonographic appearance of tearing within the tendon, in addition to periosteal and cortical changes at the enthesis, explains a significant portion of the pain experienced by patients with infrapatellar tendinopathy.