One motif of imprisonment is the loan Nora withdrew from Krogstad several years ago. At the time, Nora thought she was taking out the loan in order to liberate herself and her husband by rescuing his health. While rescuing her husband's health certainly did provide for her more security than she would have had otherwise, the loan has also been a point of imprisonment for her. For years she has had to save every penny she could from her housekeeping money, especially money for her clothing. Having to save money on clothing has been a source of emotional imprisonment for her because, as she explains to Christine, "[I]t was often very hard on me, Christine--because it is delightful to be really well dressed, isn't it?" (I). In addition, she had to earn money by finding any work she could do behind Torvald's back. One winter she "was lucky enough to get a lot of copying to do" and locked herself up in her room working until late at night (I).
Another motif of imprisonment is of course the signature Nora forged on the bond for the loan. At the time, Nora did not consider it to be a serious matter and did it to save her husband. However, now Krogstad is blackmailing her with her forged signature as a threat against her reputation and her husband's reputation in order to try and secure his job at the bank thereby imprisoning her with the forged signature.
A third motif of imprisonment we see is Dr. Rank's illness. Dr. Rank has what Nora refers to as "consumption of the spine," otherwise called Pott disease, and claims that his illness is due to Dr. Rank's father's immoral, overly indulgent character. As Nora explains to Christine, "His father was a horrible man who committed all sorts of excesses; and that is why his son was sickly from childhood" (II). As Dr. Rank explains, "My poor innocent spine has to suffer for my father's youthful amusements," such as his father's indulgences in "asparagus," "pâté de foie gras," "and heaps of port and champagne" (II). According to Dr. Rank, all of his father's indulgences wreaked havoc on his own immune system. Dr. Rank is therefore imprisoned by his father's own sins. He is paying the consequences for his father's sins by having to die young. Dr. Rank considers his upcoming premature death as an unfair imprisonment.