given when justice so requires.” Fed. R.Civ.P. 15(a). A motion to amend should be denied “only when the amendment would be prejudicial to the opposing party, there has been bad faith on the part of the moving party, or the amendment would be futile.” Edwards v. City of Goldsboro, 178 F.3d 231, 242 (4th Cir.1999) (internal quotation marks omitted). We review the decision of a district court to grant or deny a motion to amend for abuse of discretion. See id. We agree with HCMF’s contention that the proposed amendment set forth a new legal theory. HCMF originally claimed that it had a federal right under the Boren Amendment itself for DMAS to pay reasonable and adequate rates of reimbursement. See Wilder v. Va. Hosp. Ass’n, 496 U.S. 498, 509-10, 110 S.Ct. 2510, 110 L.Ed.2d 455 (1990) (<HOLDING>). In the proposed amendment, HCMF sought to
holding that title xix providers have federal rights enforceable in a  1983 action holding that health care providers could pursuant to  1983 enforce the boren amendment to the medicaid act holding that 42 usc  1396aa13a which requires states to make reasonable reimbursement to providers was enforceable by the providers pursuant to section 1983 recognizing right to privacy in receipt of health care services to the extent consistent with providing adequate medical care and the safety and good order of the facility holding that boren amendment created substantive federal right enforceable by health care providers to reasonable and adequate rates