Achilles tendon anatomy:
The Achilles tendon is the largest and strongest tendon in the human body.
It is formed from the convergence of tendons of gastrocnemius (superficial) and soleus (deep) muscles of the posterior calf.
It inserts onto the posterior calcaneus. Uniquely it lacks a true tendon sheath,
but instead is invested by a paratenon which facilitates gliding.
Achilles tendon biomechanics:
Provides energy storage during locomotion.
It increases top running speed
and reduces energy cost.
Exposed to huge forces (up to 12.5 x BW) [1]
Normal Achiles tendon imaging:
Ultrasound - parallel fibres should clearly been seen on longitudinal scanning
Fig. 1: Longitudinal ultrasound shows the normal Achilles tendon (blue arrows). The tendon is of uniform thickness and the parallel fibrillar structure is clearly seen.
References: otto chan
and the substance of the tendon should appear uniform.
The tendon should have a flat or concave contour on longitudinal scanning.
It should appear flat on axial scanning.
Fig. 2: Axial ultrasound shows normal tendon (between calipers) which is has a normal flat contour and with fibres clearly visible
No vascularity should be seen on Doppler interrogation.
MRI - the tendon should be of uniform thickness with no bulges or convexity to its contour.
It should be of homogenously low signal on all sequences.
Fig. 3: Sagittal T2-weighted MRI illustrates the normal Achilles tendon (red arrows)
Fig. 4: Axial T2-weighted MRI shows the normal Achilles tendon (red line)
References: otto chan
Achilles tendon disorders:
Pain in the Achilles tendon region is very common,
in both athletes and sedentary individuals.
Both Achilles and extra-Achilles strucutres may be responsible,
and often in combination[1].