Related Experiment Video
Updated: Oct 28, 2025
Author Spotlight: Exploring the Complexities of Achilles Tendon Injuries — Research and Future Directions
Published on: October 27, 2023
Classification by degree of twisted structure of the fetal Achilles tendon
Mutsuaki Edama1, Tomoya Takabayashi2, Hirotake Yokota2
1Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Shimami-cho 1398, Kita-ku, Niigata, 950-3198, Japan. edama@nuhw.ac.jp.
Background:
The purpose of this study was to classify the twisted structure of the fetal Achilles tendon.
Methods:
The study was conducted using 30 legs from 15 Japanese fetuses (mean weight, 1764.6 ± 616.9 g; mean crown-rump length, 283.5 ± 38.7 mm; 16 males, 14 females). According to attachment to the deep layer of the calcaneal tuberosity, cases showing only soleus attachment were classified as least twist (Type I), cases showing both lateral head of the gastrocnemius and soleus were classified as moderate twist (Type II), and cases with only lateral head of the gastrocnemius were classified as extreme twist (Type III).
Results:
Viewing the Achilles tendon from cranially shows a structure twisted counterclockwise on the right side and clockwise on the left. The Achilles tendon was Type I in 4 legs (13%), Type II in 23 legs (77%), and Type III in 3 legs (10%).
Conclusions:
The twisted structure of the Achilles tendon can be classified as early as the second trimester and is similar to that seen in adults.
Related Concept Videos
01:25Fascicle Arrangement in Skeletal Muscles
The four primary types of muscle based on fascicle arrangement are:
01:20Structural Classification of Joints
A fibrous joint is where the adjacent bones are united by fibrous connective...
01:10Ankle Joint
01:09Functional Classification of Joints
The functional classification of joints is determined by the amount of mobility between the adjacent bones. Joints are functionally classified as a synarthrosis or immobile joint, an amphiarthrosis or slightly moveable joint, or as a diarthrosis, a freely moveable joint. Fibrous and cartilaginous joints can be functionally classified as either synarthroses or amphiarthroses, whereas all synovial joints are classified as diarthroses.
Synarthrosis
An...