Goblets squats can be done with a Kettle Bell, Power Block, a Dumbbell or even a heavy Medicine Ball. The progression would be, first Prisoner Squats, Goblets Squats and then Barbell Squats. In order for your ligaments and tendons to adapt, that would be my suggested progression. Last it would be, Squats on Smith Machines, or Hack Squats. By then your ligaments and tendons should be strong enough to follow the range of motion of the machines. Muscles work when doing Free Weights Squats, are your Lower Back, Gluteus Maximus, Quadriceps and Hamstrings. Have any questions? Please feel free to ask.