2020 MIPS Measure #470: Functional Status After Primary Total Knee Replacement

Quality ID 470
NQF 2653
High Priority Measure Yes
Specifications Registry
Measure Type Outcome
Specialty Orthopedic Surgery

Measure Description

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) at one year (9 to 15 months) postoperatively



This measure is to be submitted each time a patient undergoes a total knee replacement during the denominator identification period. This measure may be submitted by Merit-based Incentive Payment System (MIPS) eligible clinicians who perform the quality actions described in the measure based on the services provided and the measure-specific denominator coding.

NOTE: 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. 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.


Measure Submission Type:
Measure data may be submitted by individual MIPS eligible clinicians, groups, or third-party intermediaries. The listed denominator criteria are used to identify the intended patient population. The numerator options included in this specification are used to submit the quality actions as allowed by the measure. The quality-data codes listed do not need to be submitted by MIPS eligible clinicians, groups, or third-party intermediaries that utilize this modality for submissions; however, these codes may be submitted for those third party intermediaries that utilize Medicare Part B claims data. For more information regarding Application Programming Interface (API), please refer to the Quality Payment Program (QPP) website.



Patients 18 years of age or older as of October 1 of the denominator identification period who had a total knee replacement procedure performed during the denominator identification period


Denominator Identification Period - The twelve-month period in which eligible patients have a denominator eligible procedure. This allows for enough time for a follow-up assessment to occur during the twelve-month performance period. The denominator identification period includes dates of procedure 10/1/2018 to 9/30/2019.

Denominator Criteria (Eligible Cases):

Patients aged ≥ 18 years by October 1 of the Denominator Identification Period


Patient procedure during performance period (CPT): 27445, 27446, 27447



All eligible patients whose functional status is greater than or equal to 37 on the Oxford Knee Score (OKS) patient reported outcome tool at one year (9 to 15 months) postoperatively


Measure Assessment Period (Performance Period) - The period of time following the procedure date that is in which a postoperative Oxford Knee Score (OKS) functional status score can be obtained.

Postoperative Assessment Oxford Knee Score (OKS) - A postoperative Oxford Knee Score (OKS) functional assessment score can be obtained from the patient one year (9 to 15 months) after the date of procedure. Assessment scores obtained via a telephone screening or prior to 9 months and after 15 months postoperatively will not be used for measure calculation.

Oxford Knee Score (OKS) Patient Reported Outcome Tool - The Oxford Knee Score (OKS) is a 12-item patient-reported outcome (PRO) tool PRO specifically designed and developed to assess function and pain after total knee replacement (TKR) surgery (arthroplasty). It is short, reproducible, valid and sensitive to clinically important changes. The OKS was designed to be completed by the patient thus minimizing potential bias unwittingly introduced by surgeons when assessing the results themselves. The PRO was designed and developed by researchers at Oxford University Innovation and the University of Oxford. A copy of the tool can be obtained below or at the following link: https://innovation.ox.ac.uk/outcome-measures/oxford-knee- score-oks/. Indicate that this tool is for use in a CMS program and licensing fees should be waived. https://innovation.ox.ac.uk/clinical-outcomes/information-for-cms-members/

OKS Target -– A patient who is assessed postoperatively at one year (9 to 15 months) after the procedure rates their functional status score as greater than or equal to 37.

NUMERATOR NOTE: The following situations are those in which the numerator targets cannot be reached and Performance Not Met (M1046) is submitted:

  • Oxford Knee Score (OKS) is not administered postoperatively at one year (9 to 15 Months)
  • Functional status is measured using a different patient-reported functional status tool or Oxford Knee Score (OKS) version
  • Postoperative Oxford Knee Score (OKS) is administered less than 9 Months or greater than 15 Months
  • Postoperative Oxford Knee Score (OKS) score is less than 37

Numerator Options:

Performance Met: Functional status measured by the Oxford Knee Score (OKS) at one year (9 to 15 months) postoperatively was greater than or equal to 37 (M1045)


Performance Not Met: Functional status was not measured by the Oxford Knee Score (OKS) at one year (9 to 15 months) postoperatively (M1141)


Performance Not Met: Functional status measured by the Oxford Knee Score (OKS) at one year (9 to 15 months) postoperatively was less than 37 (M1046)



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 babyboomers, 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 (Ong 2006). It is estimated that annual hospital charges for TKR will approach 40.8 billion dollars annually by 2015 (Kaiser-Permanente 2007).

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 Recommendation Statements

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.


PatientPost-op OKSMet Numerator Target?
Patient A39Yes
Patient B42Yes
Patient C35No
Patient D46Yes
Patient ENot assessedNo
Patient F38Yes
Patient GNot assessedNo
Patient H36No
Patient I43Yes
Patient J44Yes
Rate 60%

Register with MDinteractive