Background: Achilles tendinopathy (AT) affects ca. 10 million recreational runners in Europe; the practice of hyaluronic acid (HA) infiltration is being increasingly adopted. The aim of this pilot study was to monitor the effects of a three-local time-spaced injections regimen of HA in the treatment of AT in middle-aged runners combining for the first time viscoelastometric, biochemical, and functional methodologies with routine clinical examinations.
Methods: Eight male runners (Age 49.3 ± 3.9), diagnosed for unilateral AT, were given three ultrasound (US) guided peritendinous HA injections at the baseline (T0) and every fifteenth day with a follow-up on the forty-fifth day (T1, T2, and T3). At all-time points patients were assessed for viscoelastic tone and stiffness, maximal voluntary isometric contraction (MVIC), and pain level (Likert scale 0-5). The peritendinous effusions of the injured tendon were collected at T0 and T2 to quantify the volume variations and the IL-1β and MMP-3 levels.
Results: At T0 MVIC and pain score were significantly lower and higher, respectively, in injured tendons. The volume, IL-1β and MMP-3 levels decreased in the course of treatment and the clinical endpoints ameliorated over time. Tone, stiffness, and functional performance also varied significantly at T2 and T3, as compared to T0.
Conclusions: The sequential peritendinous injections of HA were effective in the amelioration of the clinical symptoms, as well as of the functional and viscoelastic state associated with AT. The determination of the viscoelastometric state may help to precisely evaluate the healing process in AT patients.
Keywords: Achilles tendon; hyaluronic acid; interleukin-1beta; isometric contraction; matrix metalloproteinase 3; tendinopathy; viscoelastic properties.