Kaushal, ParulRoy, TaraJacob, TonySrivastava, DeepSahni, ChetanRani, Neerja2025-01-272025-01-27202232778https://dl.bhu.ac.in/ir/handle/123456789/15048Introduction: Tendons may rarely be ossified. The calcaneal tendon (CT) is the largest in the body. The incidence and mechanism of ossification of CT is not known. Material and Methods: We carried out a morphological, radiological, histological, and immunohistochemical study on the CT of 50 (30 - male and 20 - female) human cadavers. Results: The mean length (cm) of the CT was 27.60 � 2.30 (right) and 27.51 � 2.60 (left) in males and 25.43 � 0.77 on both sides in females. The contribution to the formation of the CT from the two heads of gastrocnemius muscle was greater from medial head in 84%, lateral head in 12%, and equal in 4%. On screening the CT by C-arm radiography, slight opacification at the site of insertion of CT (bilaterally) was noted in an elderly male. Large, bilateral opacification was seen in another elderly male cadaver. Well-defined lamellar bone with osteocytes lying in lacunae and bone marrow amid the tendon collagenous tissue was noted in hematoxylin- and eosin-stained sections. The osteocytes expressed hypoxia-induced factor 1 alpha. Discussion and Conclusion: In this study, we confirmed that the radiological opacification in the CT was ossification that may have been triggered by hypoxia. � 2022 Journal of the Anatomical Society of India | Published by Wolters Kluwer - Medknow.Achilles tendonheterotopic ossificationosteocytestendocalcaneumArticlehttps://doi.org/10.4103/jasi.jasi_178_21