Total knee arthroplasty (TKA)

TKA involves removing deteriorated cartilage and bone from all three compartments of the knee joint and replacing them with metal and polyethylene implants. The procedure is most commonly indicated for end-stage osteoarthritis but also applies to inflammatory arthropathy, post-traumatic arthritis, and selected oncologic or fracture-related conditions. Medical necessity requires documented functional decline—specifically, impairment in activities of daily living (ADLs)—despite a reasonable trial of conservative management such as NSAIDs, corticosteroid injections, or supervised physical therapy.

From a coding standpoint, the primary TKA procedure is captured by CPT 27447. Routine associated steps—synovectomy, osteophyte removal, and minor bone grafting performed during the same session—are considered bundled and must not be billed separately. When both knees are replaced in the same operative session, modifier 50 applies; unilateral procedures require modifier RT or LT to establish laterality. Revision procedures are coded differently: CPT 27486 covers revision of a single component, while CPT 27487 applies when both femoral and the entire tibial components are revised.

Since January 2018, CMS removed CPT 27447 from the Medicare Inpatient-Only (IPO) list, allowing the procedure to be performed in either inpatient or outpatient hospital settings. The surgeon determines the appropriate care setting based on clinical judgment and the two-midnight rule. Medicare Advantage plans retain independent discretion in prior-authorization requirements, so payer-specific policies must be verified before scheduling. Beginning with the 2027 payment year, CMS is implementing a mandatory inpatient Patient-Reported Outcome Measure (PROM) for TKA through the IQR program, with pre-operative data collection windows starting in April 2024.

Incorrect TKA coding carries direct financial and compliance consequences. Billing CPT 27447 when documentation supports only a unicompartmental replacement, using a revision code (27486 or 27487) without clear evidence of prior implant failure, or omitting laterality modifiers are common triggers for payer audits and claim denials. Because arthroplasty procedures carry high reimbursement values, they draw disproportionate scrutiny from Medicare Recovery Audit Contractors (RACs) and commercial payers. Additionally, failure to document unsuccessful conservative therapy in the medical record—as required under CMS Local Coverage Determinations—can result in post-payment recoupment even when the procedure itself was clinically appropriate.