What causes degenerative tears and syrinx in both achilles tendons?

Excessive : Strain and stress can cause degenerative changes. I am not sure what the word syrinx means or was supposed to mean.

Weak tendon sheath: Degenerative tears in the achilles are caused by a weak sheath that covers the tendon itself. Since the sheath protects the tendon and gives it it's nourishment, if it is congenitally weaker it will create tears. This is also made worse by Cipro (ciprofloxacin) or levoquin antibiotics and some statin drugs. A syrinx is a cavity in the spinal cord (short for syringomyelia), not in the achilles.