Insertional Achilles tendinopathy : a novel link to shorter free tendons

Abstract

Background: Achilles tendinopathy is a common overuse injury among athletes, classified into mid-portion and insertional types. While existing literature primarily emphasizes mid-portion tendinopathy as the more prevalent form, emerging evidence highlights the significance of insertional tendinopathy. Variations in clinical presentation warrant further investigation, particularly regarding anatomical differences that could inform treatment strategies and rehabilitation protocols.

Purpose: This study aimed to assess the prevalence of Achilles tendon pathologies and explore anatomical differences in the length of the free tendon between insertional and mid-portion tendinopathy.

Study design: This study represents a cross-sectional analysis conducted as part of a larger longitudinal study on the mechanical properties of patients with Achilles tendinopathy.

Methods: A total of 103 patients (38.8 % males, 61.2 % females, age: 53 ± 12.8 years, body Mass Index (BMI): 30 ± 7.4 kg/m2, 60 % sedentary while 40 % active) diagnosed with Achilles tendon pathologies from across the Maltese islands were recruited for ultrasound assessments to measure tendon length and evaluate associated anatomical characteristics. Participants were categorised based on the type of tendinopathy.

Results: A higher prevalence of insertional tendinopathy (67.9 %) was identified compared to mid-portion tendinopathy (20.3 %). Notably, participants with insertional tendinopathy presented with short tendons (3.8 ± 1.4 cm, p = <0.001) compared to those with longer free tendon length in mid-portion tendinopathy (5.9 ± 1.3 cm, p = <0.001). This anatomical distinction, along with the lower attachment of the soleus muscle, may contribute to differing biomechanical properties, influencing the risk of specific tendon pathologies.

Conclusions: This study is the first to report a higher prevalence of insertional tendinopathy and to highlight the link between short free tendon length and insertional tendinopathy. This emphasizes the importance of monitoring short free tendons, as they are likely pivotal in the development of insertional tendinopathy.