An apparatus (10; 38; 38a; 38b; 500) for generating therapeutic shockwaves, comprising: a probe (38; 38a) including a first plurality of electrical connectors and configured to be coupled to a pulse-generation system (26; 400), the probe comprising a housing defining a chamber (18; 18a) and a shockwave outlet, the chamber (18; 18a) configured to be filled with a liquid; and a spark module (22; 22a; 22b; 22c) configured to be disposed in the chamber and removably coupled to the probe (38; 38a), the spark module (22; 22a; 22b; 22c) comprising: a sidewall (120, 120a, 120b) defining a spark chamber (124; 124a; 124b), the spark chamber (124; 124a; 124b) configured to be filled with a liquid (128; 128a); a second plurality of electrical connectors coupled to the sidewall (120, 120a, 120b) and configured to be electrically coupled to the first plurality of electrical connectors of the probe (38, 38a); and a plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) coupled to the sidewall (120, 120a, 120b) and disposed in the spark chamber (124; 124a; 124b) to define one or more spark gaps (412a, 412b, 412c), the plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) electrically coupled to the second plurality of electrical connectors; wherein at least a portion of the sidewall (120, 120a, 120b) comprises an acoustically permeable or transmissive material configured to permit shockwaves generated at the electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) to travel through the sidewall (120, 120a, 120b) and through the chamber (18; 18a); where the spark module (22; 22a; 22b; 22c), including the sidewall (120, 120a, 120b), the second plurality of electrical contacts, and the plurality of electrodes, is removable from the probe (38; 38a); and where the plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) is configured to receive voltage pulses from the pulse-generation system (26; 400) at a rate of between 10 Hz and 5 MHz, when the chamber (18; 18a) and the spark chamber (124; 124a; 124b) are filled with the liquid (54; 128; 128a) and the spark module (22; 22a; 22b; 22c) is coupled to the pulse-generation system (26; 400) via the probe (38; 38a), such that portions of the liquid (54; 128; 128a) are vaporized to generate shockwaves that propagate through the liquid (54; 128; 128a) and the shockwave outlet (20; 20a). a probe (38; 38a) including a first plurality of electrical connectors and configured to be coupled to a pulse-generation system (26; 400), the probe comprising a housing defining a chamber (18; 18a) and a shockwave outlet, the chamber (18; 18a) configured to be filled with a liquid; and a spark module (22; 22a; 22b; 22c) configured to be disposed in the chamber and removably coupled to the probe (38; 38a), the spark module (22; 22a; 22b; 22c) comprising: a sidewall (120, 120a, 120b) defining a spark chamber (124; 124a; 124b), the spark chamber (124; 124a; 124b) configured to be filled with a liquid (128; 128a); a second plurality of electrical connectors coupled to the sidewall (120, 120a, 120b) and configured to be electrically coupled to the first plurality of electrical connectors of the probe (38, 38a); and a plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) coupled to the sidewall (120, 120a, 120b) and disposed in the spark chamber (124; 124a; 124b) to define one or more spark gaps (412a, 412b, 412c), the plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) electrically coupled to the second plurality of electrical connectors; a sidewall (120, 120a, 120b) defining a spark chamber (124; 124a; 124b), the spark chamber (124; 124a; 124b) configured to be filled with a liquid (128; 128a); a second plurality of electrical connectors coupled to the sidewall (120, 120a, 120b) and configured to be electrically coupled to the first plurality of electrical connectors of the probe (38, 38a); and a plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) coupled to the sidewall (120, 120a, 120b) and disposed in the spark chamber (124; 124a; 124b) to define one or more spark gaps (412a, 412b, 412c), the plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) electrically coupled to the second plurality of electrical connectors; wherein at least a portion of the sidewall (120, 120a, 120b) comprises an acoustically permeable or transmissive material configured to permit shockwaves generated at the electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) to travel through the sidewall (120, 120a, 120b) and through the chamber (18; 18a); where the spark module (22; 22a; 22b; 22c), including the sidewall (120, 120a, 120b), the second plurality of electrical contacts, and the plurality of electrodes, is removable from the probe (38; 38a); and where the plurality of electrodes (100; 100a, 100b, 100c; 100, 100d-1, 100d-2, 100e, 100f; 100g) is configured to receive voltage pulses from the pulse-generation system (26; 400) at a rate of between 10 Hz and 5 MHz, when the chamber (18; 18a) and the spark chamber (124; 124a; 124b) are filled with the liquid (54; 128; 128a) and the spark module (22; 22a; 22b; 22c) is coupled to the pulse-generation system (26; 400) via the probe (38; 38a), such that portions of the liquid (54; 128; 128a) are vaporized to generate shockwaves that propagate through the liquid (54; 128; 128a) and the shockwave outlet (20; 20a).