What measurement means for total knee replacement surgery

There are more than 700,000 total knee replacement surgeries performed in the United States each year. By 2030, an estimated 3.5 million procedures will be performed annually due to the nation’s aging population and increasing obesity. Candidates for total knee replacement surgeries often have severe destruction of the knee joint associated with increasing pain and impaired function.

One way for your provider to understand your knee problems and pain, and their impact on your daily activities is by using the Oxford Knee Score (OKS) assessment. Completing the OKS before and after surgery can help both you and your doctor understand the level of pain you are experiencing. It asks 12 questions about your daily living activities in various areas, including level of pain; self-care; getting in/out of car; length of time able to walk; sitting; kneeling; night pain; interference with normal work; limping; and ability to climb or descend stairs.

Based on your answers, the score reflects the severity of the problems with your knee. The higher the score, the better your knee function is. Assessing the function and pain in your knee helps to identify the treatment options that are right for your individual needs.

The Total Knee Replacement: Pain, Function and Mobility measure reports the amount of change in pain, function and mobility based on feedback from patients who had total knee replacement. This is called a Patient-Reported Outcome (PRO) measure because it uses the patient's own rating of their pain, function and mobility as a way to measure the quality of care.

Patient outcomes are measured on a 48-point scale.

The statewide average change in score for patients who had total knee replacement surgery of all reporting medical groups is 17.1 points. This means that on a scale of 0 to 48 points, the average change in function after surgery was 17.1 points. 

Medical groups ranged between an average change of 12.54 and 18.47 points. A higher score is a sign of greater improvements in a patient’s pain, function and mobility after total knee replacement surgery.

It’s important to know that small differences in scores don’t necessarily reflect the quality of care you’ll receive with a specific medical group. It is more important to note large differences between providers, and speak with your doctor if you have questions or concerns.

Don’t see your medical group listed? While some of the medical groups in Minnesota that provided data for this measure didn’t have enough patients to have valid, reportable results, other medical groups chose not to submit data at all. For consumers, this means that some important information is missing that would help you have a better understanding of the outcomes from this surgery.

How we calculate the measure

We measure how patients feel based on their responses to a tool called the Oxford Knee Score (OKS) assessment that asks 12 questions about knee pain, function and mobility. Total knee replacement patients are asked to complete the tool before surgery and after surgery. Based on the answers, the tool calculates a simple score that shows how severe a patient’s knee problems are. By comparing the score before surgery and after surgery, we are able to report the amount of change experienced by patients.

This report is based on surgeries performed from January 1 to December 31, 2013. This information is collected under the measure name Total Knee Replacement (primary).

Risk-adjusted measures

The information reported about this measure on MNHealthScores is risk-adjusted.

Risk adjustment is a way to make it easier to compare clinics or medical groups by accounting for the differences of specific patient groups. The process should separate the clinic/medical group’s true impact on patients’ health and allow them to be compared more easily.

MN Community Measurement uses an actual-to-expected process, which is also known as a methodology. This process does not change a clinic/medical group’s result; the actual rate remains the same. Instead, each clinic/medical group’s actual rate is compared to the rate that we expected to see, based on the different types of patient characteristics seen at that clinic/medical group.

More details about our risk adjustment methodology and the variables used for the measures reported on MNHealthScores.org can be found in the most current Health Care Quality Report.