Do insertional and mid-portion Achilles tendinopathy display different material properties?

We thank Zhang et al for their letter to the editor which raises the question as to whether insertional and non-insertional (or midportion) Achilles tendinopathy have different “stiffness patterns.” This proposal is based on findings of greater “hardness” in insertional Achilles tendinopathy in the study by Zhang et al,1 and lower “elastic modulus” in the study by Coombes et al,2 which recruited participants with a clinical diagnosis of Achilles tendinopathy at either region. While plausible, there are several critical differences between the two studies that ought to be considered.