🦵 Total Knee/Hip Replacement Decision Threshold Simulator

Baseline Pain and Functional Assessment in Knee and Hip Osteoarthritis

Every replacement decision starts with a structured pain and function baseline.

• 0–20: WOMAC Pain Subscale (higher score means worse pain)
• 0–100: KOOS / HOOS Score (patient-reported joint outcome)
• 0–10: VAS Pain Scale (visual analog pain rating)
• 0–4: Radiographic KL Grade (Kellgren-Lawrence severity grade)

Pain Intensity Scoring

Rate current joint pain using a 0–10 visual analog scale.

Functional Limitation Scoring

Assess walking, stairs, and daily activity limitation on a 0–100 scale.

Conservative Therapy Trial — Exercise, Injections, and Pharmacologic Management

Guidelines require a structured non-surgical trial before considering surgery.

• 6–12 wk: Physical Therapy Trial (standard minimum duration)
• 3–6 mo: Corticosteroid Injection (typical relief window)
• 4–6 wk: NSAID Trial (first-line pharmacologic step)
• 5–10%: Weight Loss Target (reduces mechanical joint load)

Physical Therapy and Exercise

Structured strengthening and range-of-motion exercise over six to twelve weeks.

Injections and Pharmacologic Therapy

Corticosteroid or hyaluronic acid injections paired with an NSAID trial.

Evaluating Conservative Therapy Failure Before Surgical Referral

Failure is defined relative to duration, relief percentage, and function change.

• <30%: Failure Threshold (pain relief counts as failure)
• ≥3 mo: Trial Duration Required (before surgical referral)
• 2 of 2: Injection Non-Response (failed injection courses)
• persistent: Function Decline (despite adequate therapy)

Defining Treatment Failure

Failure means persistent pain and function loss despite adequate conservative care.

Referral Criteria

A failed trial of three or more months triggers surgical referral.

Calculating the Composite Surgical Threshold Score

Pain, function, and failure are weighted into a single 0–100 score.

• 65 / 100: Threshold Score Cutoff (surgical candidacy line)
• 35%: Pain Weight (share of composite score)
• 35%: Function Weight (share of composite score)
• 30%: Conservative Failure Weight (share of composite score)

Composite Score Formula

Weighted sum of pain, function, and conservative failure percentages.

Threshold Interpretation

Scores above sixty-five indicate strong surgical candidacy.

Replacement Recommended vs. Continue Conservative Management

The threshold score becomes an explicit surgery-or-wait recommendation with confidence.

• ~790k: Annual TKA Volume (US) (knee procedures per year)
• ~450k: Annual THA Volume (US) (hip procedures per year)
• 90–95%: 10-Year Implant Survival (modern prosthesis designs)
• 80–90%: Patient Satisfaction (TKA) (post-surgical outcome rate)

Recommending Replacement

A high composite score with failed conservative care supports proceeding to surgery.

Continuing Conservative Management

Below-threshold scores favor ongoing non-surgical treatment and reassessment.