The invention provides anti-myostatin antibodies and methods of using the same. In some embodiments, an isolated anti-myostatin antibody of the present invention binds to mature myostatin, and uptake of the antibody into cells is enhanced when complexed with the antigen. The invention also provides isolated nucleic acids encoding an anti-myostatin antibody of the present invention. The invention also provides host cells comprising a nucleic acid of the present invention. The invention also provides a method of producing an antibody comprising culturing a host cell of the present invention so that the antibody is produced. Anti-myostatin antibodies of the present invention may be for use as a medicament. Anti-myostatin antibodies of the present invention may be for use in treating a muscle wasting disease. Anti-myostatin antibodies of the present invention may be for use in increasing mass of muscle tissue. Anti-myostatin antibodies of the present invention may be for use in increasing strength of muscle tissue.