Neovascularization in abnormal tendons shown on Doppler sonography has a varied relationship with pain and outcome. Some studies have reported an absolute association [1] and others a less clear relationship [2–4]. Overall, however, these studies indicate that abnormal tendons with detectable vascularity seem to be more painful than those without vascularity. Imaging vascularity in tendons can be problematic because the detection of vascularity with Doppler sonography is sensitive to muscle stretch and contraction, both of which can eliminate detectable blood flow. This is now clearly understood, and most examiners now ensure a relaxed muscle when the tendon is imaged.

The activity of the tendon before imaging may have a crucial effect on tendon vascularity when imaged with Doppler sonography. It is known that resting tendons have a low blood flow and that even exercise may increase it only submaximally [5]. To our knowledge, only one previous article has reported the effect of activity on tendons; that study examined patellar tendons of subjects before and after playing a basketball game [6]. Three of four tendons that were vascular after the game had vascularity before the game. It is unclear from that article how much change was apparent in those tendons because no attempt to quantify the change was made.

Although there are now several articles on tendon vascularity, none of the authors have reported the activity of the person before imaging or described a standardized warm-up before imaging. Tendon imaging is usually done in a clinical setting, often after the patient has sat quietly waiting for examination for a variable period of time. If activity affects vascularity, then this tendon “quiet time” before imaging may mean that all vascularity that is present in the tendon is not detected because of a lack of blood flow in the vessels. This pilot study aimed to examine patellar tendons in subjects before and after playing a volleyball game and quantify the change in tendon vascularity due to intense activity of the musculotendinous unit.

Seventeen volleyball players (three grades ranging from elite to domestic competitions) with known tendon vascularity were taken from a larger cohort of players. Their patellar tendons were examined before and after (within 1 hr) a competitive game of volleyball with sonography by an experienced musculoskeletal radiologist. The examinations were performed with the subject supine and the knee extended, and care was taken to ensure relaxation of the quadriceps muscle. Approval for the study was gained from the La Trobe University Human Ethics Committee, and all subjects provided informed consent.

Tendons were imaged in the sagittal plane with both gray-scale and color Doppler sonography using a unit with a 13.5-MHz linear transducer (Acuson CV70, Siemens Medical Solutions). Color Doppler settings were standardized with a gain of 68 dB, sensitivity of 8 cm/sec, and pulse repetition frequency of 1,250 Hz. These settings were chosen because they represent the mid range of settings used to show tendon vascularity and can depict vascularity without excessive artifact. A line of known length was placed on each image so vessel length could be determined later in millimeters.

During color Doppler examinations, vascularity in the sagittal plane was recorded and then each vessel visible in the sagittal plane was measured from the electronic picture. Vessels measured to be less than 1 mm were not counted, and vessels that were not continuous but had breaks of less than 1 mm between ends were considered to be a continuous vessel. Vessels clearly in the fat pad or superficial to the tendon were not counted, and those more difficult to determine the location were considered to be tendon vessels. This measurement technique has shown excellent intratester and intertester reliability [7]. Vessel length measurements were chosen because it was the simplest way of measuring change in tendon vascularity.

The median length of the vessels before the game was 7.3 mm (range, 1–21 mm). After the game, the median length of vessels had increased to 19.9 mm (range, 1–43 mm) (Fig. 1A, 1B). There was a significant difference between the vascular scores before and after the game (Wilcoxon's signed rank test: z = –3.5, p < 0.001).

The median change in vessel length from pregame to postgame measurements was 8 mm (range, 0–27 mm). When relative change is considered, the mean change can be equated to a 2.7-fold increase in detectable vascular length (Table 1).

This study shows the impact of activity on the ability of color Doppler sonography to detect tendon vascularity. Tendons in this study responded variably to activity: In some, the detectable vascularity increased enormously, whereas some tendons showed little response. We expected, due to the nature of volleyball, that all athletes in this study would have been equally active and we inferred that the increase in vascularity is tendon-dependent—not activity-dependent.

The unclear relationship between pain and tendon vascularity may in part be explained by this study. Our findings indicate that moderately athletic exercise significantly enhances the detection of tendon blood flow. Therefore, those tendons that are painful but not vascular may need to be exercised to fully evaluate tendon vascularity.

In a previous study, we found that tendons could be vascular and not vascular on different days [8], so athletes with abnormal tendons and no vascularity should be imaged after exercise to examine whether quiescent vascularity exists.

An investigation into how much activity is required to see the maximum vascularity is needed, and from that investigation, a standardized protocol to image tendon vessels should be established. Only then can we be sure that all vascularity present is being detected. Because treatment of the tendon vessels is available and reported to positively affect pain [9], it is clinically important that all vessels are identified.

In conclusion, this pilot study suggests that activity affects the vascularity detectable with color Doppler sonography. This effect should be considered when imaging abnormal tendons; further investigation is warranted to develop a standardized warm-up procedure that can be used when imaging tendons.

Address correspondence to J. L. Cook ([email protected]).