An ultrasound coupling device for a wearable, portable, therapeutic ultrasonic system, the ultrasound coupling device comprising: a coupling compartment comprising: a chamber having a continuous side wall and an opening on a first end, and a flexible flange region extending outward from at least a portion of the continuous side wall of the chamber; wherein said ultrasound coupling device is configured for operative coupling with a low-profile ultrasound transducer and an ultrasound conductive gel so as to apply ultrasonic energy to a subject, wherein the ultrasound coupling device further comprises an enabler mechanism which enables the operation of the low-profile ultrasound transducer only if the enabler mechanism and transducer are in contact with one another; wherein said continuous side wall is configured to hold said low-profile ultrasound transducer completely within the chamber so that a front ultrasound emitting surface of the low-profile ultrasound transducer faces outward toward the chamber opening but does not extend beyond a first end of the continuous side wall of the chamber, said front ultrasound emitting surface configured to control the direction and wave pattern of ultrasonic energy emitted from the low-profile ultrasound transducer, wherein said continuous side wall is configured to hold the ultrasound conductive gel within the chamber and operative to keep the ultrasound conductive gel in simultaneous direct contact with the subject and with at least a portion of the front ultrasound emitting surface of the low-profile ultrasound transducer, and wherein said continuous side wall is configured so that when said ultrasound coupling device is operatively coupled together with said low-profile ultrasound transducer and the ultrasound conductive gel, and when the first end of the continuous side wall is in contact with the subject, the first end of the continuous side wall is suitable to keep a quantity of the ultrasound conductive gel within the chamber. a coupling compartment comprising: a chamber having a continuous side wall and an opening on a first end, and a flexible flange region extending outward from at least a portion of the continuous side wall of the chamber; a chamber having a continuous side wall and an opening on a first end, and a flexible flange region extending outward from at least a portion of the continuous side wall of the chamber; wherein said ultrasound coupling device is configured for operative coupling with a low-profile ultrasound transducer and an ultrasound conductive gel so as to apply ultrasonic energy to a subject, wherein the ultrasound coupling device further comprises an enabler mechanism which enables the operation of the low-profile ultrasound transducer only if the enabler mechanism and transducer are in contact with one another; wherein said continuous side wall is configured to hold said low-profile ultrasound transducer completely within the chamber so that a front ultrasound emitting surface of the low-profile ultrasound transducer faces outward toward the chamber opening but does not extend beyond a first end of the continuous side wall of the chamber, said front ultrasound emitting surface configured to control the direction and wave pattern of ultrasonic energy emitted from the low-profile ultrasound transducer, wherein said continuous side wall is configured to hold the ultrasound conductive gel within the chamber and operative to keep the ultrasound conductive gel in simultaneous direct contact with the subject and with at least a portion of the front ultrasound emitting surface of the low-profile ultrasound transducer, and wherein said continuous side wall is configured so that when said ultrasound coupling device is operatively coupled together with said low-profile ultrasound transducer and the ultrasound conductive gel, and when the first end of the continuous side wall is in contact with the subject, the first end of the continuous side wall is suitable to keep a quantity of the ultrasound conductive gel within the chamber.