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Tensile strength

Achilles' Tendon Pathologies (ATP)

Achilles’ Tendon Pathologies (ATP) include tendinosis and paratenonitis, involving inflammation, thickening, or degeneration of the tendon. Achilles' Tendon rupture is another pathology common among athletes, occurring quite often during ball-game.


While one genetic make-up can double your chances for ATP, another make-up increases tensile strength and enhances tendon repair capability.

The Achilles tendon is the largest tendon in the body. It connects the calf muscles to the heel bone. Achilles’ Tendon Pathologies (ATP) include tendon rupture, tendinosis and paratenonitis. Tendinosis and paratenonitis involve inflammation and thickening, or disarray and degeneration of the tendon. Achilles' tendon rupture tears the tendon fibers. 

ATP is much more frequent among men, most often in 30 to 40 year-old athletes, and usually not triggered by any contact or collision. Complete rupture is mostly associated with playing ball games. Inflammation in the tendon (tendinosis) increase the risk of rupture, as well as Cortisone injections into the Achilles' tendon and use of Fluoroquinolone antibiotics.

On top of that, genetic variants of genes involved with tensile flexibility and strength can predispose to occurrence of ATPs.


Genomic coordinates (GRCh38): 20:35,433,346-35,454,745


The GDF5 gene is associated with Achilles tendon tensile strength. Variants of the gene were associated with predisposition for ATP, as well as time to recovery.

GDF-5 is a growth factor involved in bone and cartilage formation. It regulates differentiation of chondrocytes, the cells that produce and maintain the cartilage matrix. 

The central role of the GDF-5 gene in maintaining healthy cartilage is evident.  C allele carriers have been shown to have enhanced tendon repair capacity and are at reduced risk for injury in the first place, while homozygous TT genotype individuals were twice as likely to develop Achilles’ tendon pathology.

The figure below sums individuals with and without ATP from two studies. It shows how ATP is significantly more frequent among individuals carrying the TT genetic set-up.


Another genetic risk factor is the COL5A1 gene set-up. Individuals from multiple ethnicities carrying the COL5A1 CC genotype had a significantly decreased risk of developing chronic Achilles tendinopathy.

Genomic coordinates (GRCh38): 9:134,641,788-134,844,842


The COL5A1 gene encodes for the collagen a1 chain. Collagens begin as rope-like procollagen molecules, made up of various types of collagen chains. Type V collagen is produced out of the a1 and a2 chains
The collagen molecules arrange themselves into long, thin fibrils with another form of collagen, type I. Type V collagen regulates the width (diameter) of those fibrils. Studies suggest that type V collagen also controls the assembly of other types of collagen into fibrils in several tissues. Variations in the a1 chain can modulate the biomechanical properties of muscle-tendon units, such as stiffness and durability.

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