Introduction Neovascularization of tendon is one of the characteristics in patellar tendinopathy. It had been hypothesised that the vessels or the nerves accompanying the vessels were involved in the pain mechanism in this chronic pathology. [Cook, 2004] Due to the different methods used to categorise or quantify the vascularity change by researchers [Hoksrud, 2009], the relationship between vascularity and pain is still controversial. The aim of this study was to correlate findings on vascularity using power Doppler ultrasonography (PDU) and pain measured by visual analogue scale (VAS) in patients with patellar tendinopathy.
Methods PDU was performed on thirty-five jumping athletes (age range: 18–35 years, mean age 22.9 years) with patellar tendinopathy (21 unilateral, 14 bilateral). The vascularity was quantified using ultrasound images by a customised software program. Vascular index (VI) was calculated as the ratio of the number of colour pixels to the total number of pixels within a standardised selected area of proximal patellar tendon. The higher VI, the more vascular is the region. The tendons were further categorised into minimal- or moderate-vascularized groups with reference to classification rated by an experienced sonographer. The athlete then rated their knee pain level using VAS on a 10-cm continuous line marked “no pain” on one end and “worst pain” on the other, recalling the maximal pain level during activities in the last 7 days.
Results Tendons VI were positively correlated to pain level in both groups (r = 0.49; p = 0.03 in minimal-vascularized group; r = 0.57; p = 0.03 in moderate-vascularized group). However, when combining both groups, the correlation was not significant (r = 0.26, p = 0.14).
Discussion The computerised vascular index could be one of the indicators to reflect the severity or subjective pain level of athletes suffering from patellar tendinopathy. This study suggested that categorization was indicated to reflect this correlation. The pain mechanism in tendinopathy might be different in tendons with minimal- or moderate-vascularisation.
References Cook, et al. Clin J Sport Med. 2004;14:296–299
Hoksrud, et al. Am J Sports Med. 2009;36:1813–1820