Defending against assailants with weapons is a very dangerous situation. Often, I would advise that if all the assailant wants is your money or your belongings, then just give it to him for it’s not worth risking your life for the sake of material things. Remember that facing an assailant with a knife or any type of weapon puts you in a grave disadvantage.
The first photo shows the assailant holding the defender from behind with a knife on the person’s throat. The second photo shows the defender quickly grabbing the assailants weapon hand to control the attacker’s movement. He continues to move by turning inside toward the assailant while maintaining his hold as seen in the third photo. The defender then turns to break free from the hold while putting pressure on the assailant’s elbow using his shoulder as leverage as seen in the fourth photo. In the fifth photo, the defender finally pins and controls the assailant to the ground.