It happened on San Ramon Avenue near 4th Street just before 9 am Thursday.
Police say a 65-year-old man using a walker was approached by a 45-year-old man with a wrench.
Authorities say the older man was hit with the wrench multiple times and eventually used his walker as self-defense.
The older man then ultimately pulled a knife out of his walker and stabbed the suspect in the arm and chest.
Authorities say the suspect ran off before being taken into custody.
He is being treated at Community Regional Medical Center and will be booked into the Fresno County Jail once medically cleared.