Functional Status After Primary Total Knee Replacement
For patients age 18 and older who had a primary total knee replacement procedure, functional status is rated by the patient as greater than or equal to 37 on the Oxford Knee Score (OKS) or a 71 or greater on the KOOS, JR. tool at one year (9 to 15 months) postoperatively.
Last updated: January 15, 2026
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Estimate only — actual CMS scoring may vary based on reporting method, data completeness, and annual rule updates.
📖Clinical Rationale
Annually there are over 500,000 total knee replacement (TKR) procedures performed in the United States. It is projected that by 2030 the volume of this procedure will increase to over 3.48 million per year due to the aging baby- boomers, increased obesity and indications for TKR that extend to both younger as well as older patients (AAOS 2006 Kurtz).
From 2000 to 2006, the Medicare TKR rate overall in the United States increased 58%, from 5.5 to 8.7 per 1000 and TKR revisions currently represent 8.2% of all Medicare dollars spent. It is estimated that annual hospital charges for TKR will approach 40.8 billion dollars annually by 2015. For the Minnesota Medicare population in 2006, 9,856 patients underwent a primary hip or knee replacement procedure (DRG 544) and 1,174 patients had a hip or knee revision (DRG 545).
Nationally, for DRG 544 the average charge per hospitalization was $38,447 with an average payment of $11,916 (Value driven health care 2008 CMS). Target was derived from a study “Patient acceptable symptom states after total hip or knee replacement at mid-term follow-up” [Kuerentjes JC, Van Tol FR Bone Joint Res 2014; 3:7–13]. Receiver operating characteristic (ROC) curves identified a PASS threshold of 42 for the Oxford Hip Score (OHS) after Total Hip Replacement (THR) and 37 for the OKS after TKR.
THR patients with an OHS greater than or equal to 42 and TKR patients with an OKS greater than or equal to 37 had a higher NRS for satisfaction and a greater likelihood of being willing to undergo surgery again. The Patient Acceptable Symptom State (PASS), the highest level of symptom beyond which patients consider themselves well. PASS was compared to post-op OKS to determine an equivalent OKS threshold.
OKS score greater than or equal to 37 indicates the achievement of an acceptable symptom state and correlates with a higher numeric rating scale for satisfaction [ROC curves PASS threshold of 37 with sensitivity of 76.3% and specificity of 76.5%].
📝Clinical Recommendations
The American Association of Hip and Knee Surgeons (AAHKS) Total Knee Replacement Performance Measurement Set 2013 indicates a focus on collecting patient risk factors and implementing process measures with a future focus on outcome measures.
📋Implementation Notes
This measure contains one strata defined by a single submission criteria. This measure produces a single performance rate. For the purposes of MIPS implementation, this procedure measure is submitted each time a procedure is performed during the performance period. The most recent quality data code will be used if the measure is submitted more than once.
This measure is a target-based measure, where the numerator is met by having a one-year postoperative Oxford Knee Score (OKS) greater than or equal to 37 or a KOOS, JR. score greater than or equal to 71. It is expressed as a proportion or rate. Patients having received a primary total knee replacement procedure who are not assessed for functional status postoperatively remain in the denominator and are considered as not meeting the target.
The measure intent is that MIPS eligible clinicians will submit all denominator eligible procedures for performance calculation.
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