Knee Replacement Prior Authorization: Criteria Insurers Use and How to Prepare

Knee Replacement Prior Authorization: Criteria Insurers Use and How to Prepare

Knee replacement surgery can be life-changing for people with advanced knee arthritis, but getting it approved often depends less on how much it hurts and more on whether the chart tells a complete, “medical necessity” story. Prior authorization is the process insurers use to confirm that a planned knee replacement meets their coverage criteria before surgery is performed. If the documentation is thin, missing key details, or inconsistent, insurers may delay, request more information, or deny the request.

This article walks you through the most common knee replacement prior authorization criteria insurers use, the specific documentation they tend to look for, and a practical checklist that helps prevent denials. You’ll also learn how conservative treatment history, imaging reports, daily function limitations, and exam findings should be written so the request is easy to approve.

Important note: Requirements vary by plan, state, and utilization management vendor. Still, most insurers follow a similar evidence-based structure—pain and functional loss + objective findings + failure of appropriate non-surgical care + correct procedure selection. The examples below reflect published medical policies and coverage guidance from multiple major payers. ^[1]

Most payers frame “medical necessity” for knee replacement around four pillars:

1. A qualifying diagnosis (commonly osteoarthritis, inflammatory arthritis, osteonecrosis, or post-traumatic arthritis). ^[1]
2. Significant symptoms and functional impairment, typically documented as pain and limitations that interfere with activities of daily living. ^[1]
3. Objective evidence on imaging and exam, such as reduced range of motion, swelling or effusion, deformity, antalgic gait, and radiographic changes consistent with moderate-to-severe arthritis. ^[1]
4. Failure of appropriate conservative management (or documentation explaining why conservative care is inappropriate in severe cases). ^[1]

If any of those pillars are missing—especially conservative care dates/duration or the imaging narrative—prior authorization becomes harder.

Utilization reviewers are often scanning for specific items:

• Do the notes clearly describe disabling pain and limited function?
• Does the physical exam show objective impairment?
• Does imaging show moderate-to-severe osteoarthritis (or equivalent)?
• Is there a clear timeline showing failed non-surgical management?
• Does the requested procedure match the documented condition (total vs partial knee replacement)?

Many denials happen because the knee is truly bad—but the record reads like a short complaint rather than a complete medical necessity narrative.

Below is a documentation checklist that maps to common insurer policy language. Use it whether you are the patient, the surgeon’s office, a case manager, or a medical documentation team supporting authorizations.

Your submission should clearly state:

• Primary diagnosis (for example, osteoarthritis, rheumatoid arthritis, osteonecrosis, or post-traumatic arthritis). ^[1]
• The requested procedure (for example, total knee arthroplasty / total knee replacement or unicompartmental knee replacement).
• The side (right/left) and compartments involved (medial/lateral/patellofemoral when relevant).

Why this matters: some policies explicitly tie total knee replacement to multi-compartment disease, while partial knee replacement tends to require single-compartment disease and intact ligament stability, depending on plan.

Insurers repeatedly refer to pain and functional disability that interferes with activities of daily living. ^[1]

Strong documentation includes specific examples such as:

• Walking tolerance (for example, “must stop after 1–2 blocks due to pain”)
• Stair climbing difficulty (for example, “requires handrail; one step at a time”)
• Sitting to standing transfers (for example, “needs armrests; slow and painful”)
• Sleep disruption from pain
• Work limitations (standing, kneeling, lifting, climbing)
• Use of assistive devices (cane, walker, brace)

If you have standardized patient-reported outcome measures, include them. Some medical policies even reference tools like the Knee Injury and Osteoarthritis Outcome Score as a way to document pain and function. ^[2]

Tip: Write function limits as before/after comparisons: what the patient could do six months ago vs now.

Many policies expect objective findings such as:

• Limited range of motion
• Crepitus
• Effusion or swelling
• Pain with passive range of motion
• Antalgic gait
• Alignment issues (varus/valgus deformity) ^[1]

Example insurer language includes “limited range of motion, crepitus, or effusion” and the presence of pain with passive range of motion and antalgic gait. ^[1]

Practical documentation tip: Don’t just write “knee pain.” Add 4–6 exam bullets with measurable details (range of motion, gait, effusion grade, tenderness location, deformity).

Across payers, plain radiographs are the most common “must-have.” A Cigna clinical resource notes that for persistent knee pain or ineffective conservative treatment, knee x-rays are recommended, and that knee magnetic resonance imaging is typically not necessary for routine knee replacement workup. ^[3]

Payers often do not want “x-ray shows osteoarthritis” as a single line. They want the imaging report to describe severity. Examples from payer policies include:

• Kellgren-Lawrence grade 3 or 4 (moderate-to-severe osteoarthritis) ^[1]
• “Definite narrowing of joint space with sclerosis and possible deformity” or “large osteophytes, marked narrowing of joint space, severe sclerosis, definite deformity.” ^[5]
• “Bone-on-bone” articulation in weight-bearing compartments as a rationale to shorten or bypass conservative care requirements in severe cases. ^[1]

Recency of imaging matters:

Some policies specify that radiology or imaging should be completed within a defined timeframe before surgery (for example, within 12 months). ^[2]

When insurers request the actual images:

Some payers may request not only the report, but the specific diagnostic images that demonstrate the abnormality. UnitedHealthcare notes that, upon request, they may require the actual diagnostic images and outlines detailed imaging interpretation elements they want documented. ^[4]

Most knee replacement authorization denials trace back to one problem: the file does not clearly prove appropriate non-surgical management was tried for long enough—or the dates are unclear.

Conservative management often includes a combination of:

• Non-steroidal anti-inflammatory medications or acetaminophen (when appropriate)
• Activity modification
• Physical therapy or a structured home exercise program
• Injections (commonly intra-articular corticosteroid injections)
• Bracing and assistive devices
• Weight management counseling when relevant ^[4]

• Aetna describes a “history of unsuccessful conservative therapy” and specifies a 12- or 24-week requirement depending on age and body mass index, with exceptions for severe bone-on-bone disease, severe angular deformity, or advanced osteonecrosis/collapse. ^[1]
• UnitedHealthcare’s documentation update describes conservative care timing expectations that must be identifiable in the clinical documentation, including medication for at least 3 weeks, physical therapy or home exercise for 12 weeks, and activity modification for 12 weeks (and notes that a corticosteroid injection may be used in place of medication in certain cases). ^[4]
• Premera includes documentation requirements listing medication options and physical measures such as physical therapy and activity restriction for 12 weeks or more, and also notes that some physical measure trials may not be required when imaging demonstrates bone-on-bone severity. ^[2]
• Medicare coverage guidance similarly describes cases where pain persists despite non-steroidal anti-inflammatory medications and other conservative therapies such as steroid injections and physical therapy. ^[5]

A strong prior authorization packet does not just list treatments—it provides:

• Start and end dates (or at least month/year)
• Frequency and duration (for physical therapy visits or home exercise plan)
• Patient response (what improved, what did not, why it failed)
• Why a treatment was stopped (side effects, contraindications, inability to tolerate)

Bad documentation: “tried physical therapy.”

Good documentation: “completed 12 weeks of supervised physical therapy from May to July 2025 focusing on quadriceps strengthening and range of motion; persistent pain with stairs and walking; no durable functional improvement.”

A Medicare Local Coverage Determination explains knee arthritis symptoms that can support the need for surgery, including severe limitations in activities of daily living (difficulty walking, squatting, climbing stairs), pain worse with activity, swelling not relieved by rest, stiffness, and lack of relief after conservative therapies. ^[5]

In other words, insurers want the narrative that:

• the knee disease is real and severe (imaging + exam),
• the symptoms are function-limiting (daily activities), and
• reasonable non-surgical options were tried or aren’t appropriate.

If you are assembling documentation, aim for a packet that a reviewer can approve quickly:

Include:

• Diagnosis and side
• Procedure requested
• Key functional limitations (3–5 bullets)
• Key exam findings (4–6 bullets)
• Imaging summary with severity and date
• Conservative management timeline (with dates and outcomes)
• Any exception rationale (for example, bone-on-bone disease, severe deformity) ^[1]

• Office visit note with history and exam
• Radiology report (and images if requested) ^[4]
• Physical therapy notes or discharge summary
• Injection procedure note(s)
• Medication trials (visit note, medication list, or pharmacy record)
• Prior operative reports if revision is requested

Insurers may request “supporting medical records documenting clinical findings [and] conservative management.” ^[1]

1) “Insufficient conservative management”: ^[5]

Fix: Re-submit with a dated timeline (medication + physical therapy or home exercise + activity modification + injection when applicable) and document the outcome clearly. ^[4]

2) “Imaging does not show severity”:

Fix: Include the radiology report that describes joint space narrowing, osteophytes, sclerosis, deformity, and severity grading when available. ^[5]

3) “Functional impairment not documented”:

Fix: Add activities of daily living limitations and measurable walking/stair tolerance in the office note. ^[1]

4) “Requested procedure doesn’t match disease pattern”:

Fix: Clarify compartments involved, ligament status when relevant, and why total vs partial knee replacement is appropriate.

5) “Missing required documentation elements”:

Fix: Some payers want imaging interpretation elements and may request images; ensure the report includes a full impression and relevant details. ^[4]

Severe “bone-on-bone” arthritis:

Some policies recognize that in severe cases, extensive conservative management may be inappropriate or not required. Aetna and Premera both describe exceptions tied to bone-on-bone articulation or the most severe imaging grades. ^[1]

Osteonecrosis or avascular necrosis:

Insurers often allow knee replacement when imaging demonstrates osteonecrosis/avascular necrosis and joint-sparing options are not appropriate. ^[1]

Fracture or malignancy:

Payers typically list fracture scenarios (for example distal femur fracture not suitable for fixation) and limb salvage for malignancy as indications for knee arthroplasty. ^[6]

Even if the surgeon’s office submits the prior authorization, patients can help by ensuring the record reflects reality:

• Keep a simple symptom log (walking tolerance, sleep disruption, stairs) for your visit.
• Bring a list of non-surgical treatments already tried (medications, injections, therapy dates).
• If physical therapy was done, ask the clinic for a discharge note or progress summary.
• Confirm your imaging is recent enough and that the surgeon has the report.

The goal is not to “game” the system—it is to ensure the insurer sees a complete medical picture consistent with published criteria.

A denial is not the end; it is usually a documentation problem or a criteria mismatch.

Step 1: Identify the denial reason precisely:

Is it missing conservative therapy? Imaging? Function documentation?

Step 2: Submit a targeted reconsideration:

Add only what is missing—don’t bury the reviewer in irrelevant pages.

Step 3: Request a peer-to-peer review when appropriate:

Peer-to-peer reviews work best when

• imaging severity is clear
• conservative care is documented, but the reviewer missed it, or
• an exception applies (for example severe bone-on-bone disease).

Step 4: Appeal with policy language and chart excerpts:

Use the payer’s own medical policy phrasing (for example: “pain and functional disability interfering with activities of daily living,” “radiographic evidence of moderate-to-severe osteoarthritis,” “unsuccessful conservative management”). ^[1]

Before submission, verify the packet includes:

• Diagnosis, side, and procedure requested
• Pain description + concrete activities of daily living limitations ^[5]
• Physical exam findings: range of motion, effusion, crepitus, gait, deformity ^[1]
• X-ray report with severity descriptors (or severity grade) ^[3]
• Imaging date within payer timeframe (commonly within 12 months, plan-dependent) ^[2]
• Conservative management timeline with dates and outcomes (medications, physical therapy or home exercise, activity modification, injections when applicable) ^[4]
• Exception rationale if conservative care is not appropriate (for example bone-on-bone disease, severe deformity) ^[1]
• Attachments: visit notes, physical therapy notes, injection notes, radiology report (and images if requested) ^[4]