MCID in Orthopedics: How It Relates to SCB and PASS

A patient-reported outcome score can improve without telling the full story of a patient's recovery. A change may be meaningful, substantial, or large enough to leave the patient satisfied with their current state. Those are related outcomes, but they are not interchangeable.

Minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptom state (PASS) give three different ways to interpret patient-reported outcome measures in orthopedic care. MCID asks if the amount of change was meaningful. SCB sets a higher bar for improvement. PASS asks a different question: Has the patient reached a state they consider satisfactory?

Understanding the distinction matters as patient-reported outcomes become more closely tied to orthopedic performance measurement. CMS, for example, uses substantial clinical benefit thresholds for HOOS, JR. and KOOS, JR. when evaluating improvement following total hip and total knee arthroplasty.¹

For a broader introduction to minimal clinically important difference, including how MCID is calculated and how it differs from minimal detectable change, see our guide to MCID.

MCID, SCB, and PASS answer different questions

MCID, SCB, and PASS are all used to put clinical meaning behind patient-reported outcome scores, but each describes a different aspect of treatment response.

The distinction between change and state is especially important.

MCID compares a patient's postoperative or follow-up score with where they started. SCB does the same but applies a higher threshold. PASS typically focuses on the score the patient has reached rather than the size of the improvement needed to get there.

This means two patients can have very different outcomes even when one shows a larger numerical improvement.

Consider a simplified example:

• Patient A moves from a score of 35 to 60, a 25-point improvement.

• Patient B moves from 65 to 75, a 10-point improvement.

Patient A experienced substantially more change. Depending on the measure and validated threshold, that patient may meet MCID or SCB.

Patient B improved less but finished with the higher absolute score. That patient may be more likely to reach a PASS threshold.

Neither interpretation is necessarily more correct. They answer different questions about the outcome.

Why meaningful improvement is not the same as an acceptable outcome

MCID is useful because statistical change alone does not establish that a patient experienced a difference that matters.

But crossing an MCID threshold also does not mean the patient considers their current health satisfactory.

That distinction is the reason PASS can add another layer of context.

A patient with severe preoperative symptoms may experience a large improvement following surgery and still have considerable pain or functional limitations. The patient may exceed MCID and even SCB while remaining below an established PASS threshold.

By contrast, a patient who starts closer to a desirable health state may require relatively little improvement to finish at a level they consider acceptable.

Recent research in total joint arthroplasty illustrates how far these thresholds can differ.

A 2026 systematic review examining HOOS, JR. and KOOS, JR. thresholds found reported HOOS, JR. PASS values ranging from 73.5 to 81.0 and KOOS, JR. PASS values ranging from 63.7 to 71.0. The review also found SCB thresholds of 22 points for HOOS, JR. and 20 points for KOOS, JR.²

The difference in how the measures are expressed is important:

SCB asks how far the patient traveled. PASS asks where the patient ended up.

Used together, they provide a fuller view of an orthopedic outcome than either measure can provide alone.

MCID values can vary considerably

There is no universal MCID that applies across orthopedic outcome measures, procedures, populations, and follow-up periods.

Even studies examining the same instrument can produce substantially different thresholds.

The same 2026 systematic review found that distribution-based MCID values for HOOS, JR. ranged from 3.9 to 11.0 points. Anchor-based estimates ranged from 14.8 to 38.1 points. For KOOS, JR., distribution-based values ranged from 4.0 to 8.7 points, while anchor-based estimates ranged from 14.0 to 30.7 points.²

Those ranges demonstrate why an MCID should rarely be presented as a universal number attached to an instrument.

Why do MCID estimates differ?

One major reason is methodology.

Anchor-based approaches compare changes in an outcome measure with an external reference, such as a patient's assessment of their own improvement.

Distribution-based approaches estimate meaningful change using statistical characteristics of the collected scores.

Because these approaches measure clinical importance from different perspectives, they can produce very different values.

The patient population can also influence the threshold. An MCID derived among patients undergoing primary total knee arthroplasty may not apply to a different procedure, diagnosis, or stage of recovery.

Other factors include:

• Baseline symptom severity

• Follow-up interval

• Outcome instrument

• Procedure type

• Patient characteristics

• Definition of meaningful improvement

• Statistical method used to select the threshold

Orthopedic research has reported similar variability beyond total joint replacement. Systematic reviews of knee arthroplasty, adult spinal deformity, and hip arthroscopy have also identified differences in reported MCID, SCB, and PASS thresholds across instruments and study methods.³

The practical implication is straightforward: an MCID value should carry its context with it.

How SCB raises the bar beyond MCID

MCID is intended to identify the smallest meaningful improvement. SCB asks if the magnitude of improvement was substantially greater.

A patient may therefore meet MCID without meeting SCB.

That distinction can be valuable when evaluating procedures that commonly produce large changes in pain and physical function. In those cases, simply asking if a patient improved enough to clear the minimum meaningful threshold may set a relatively low bar.

SCB provides a way to identify patients who experienced a larger degree of benefit.

This concept has moved from research into formal orthopedic quality measurement.

CMS's total hip and knee arthroplasty patient-reported outcome performance measure assesses improvement using HOOS, JR. for hip replacement and KOOS, JR. for knee replacement. CMS defines substantial improvement as an increase of at least:

• 22 points on HOOS, JR. following total hip arthroplasty

• 20 points on KOOS, JR. following total knee arthroplasty¹

CMS describes the hospital-level result as the proportion of eligible patients who meet or exceed the applicable SCB threshold, adjusted for patient risk factors.¹

That makes the distinction between MCID and SCB more than an academic one. Organizations collecting orthopedic PROM data may encounter clinically meaningful thresholds directly within quality measurement and public reporting programs.

CMS began publicly reporting hospital participation and response-rate data for the THA/TKA patient-reported outcome measure before the measure's transition to mandatory reporting. CMS states that risk-standardized improvement results are scheduled to become publicly available beginning in 2027.⁴

Using MCID, SCB, and PASS without treating them as universal cutoffs

These thresholds can make PROM data easier to interpret, but they should not become pass-or-fail labels for individual patients.

The first question should be:

Does the threshold match the outcome measure, procedure, population, and time point being evaluated?

A published MCID derived at one year after total knee arthroplasty should not automatically be transferred to a different postoperative interval. The same caution applies when moving thresholds between surgical procedures or patient populations.

Report the source of the threshold

When possible, document or report:

• The outcome instrument

• The threshold being applied

• The procedure or population used to derive it

• The follow-up period

• The derivation method

This makes it easier for readers to understand what a statement such as "the patient achieved MCID" actually represents.

Avoid describing MCID as treatment success

Crossing an MCID threshold means the patient achieved a specified amount of meaningful change according to the method used to derive that threshold.

It does not automatically mean the treatment was a success.

A patient's pain, function, complications, goals, satisfaction, and final health state can tell a different story.

This is where SCB and PASS can improve interpretation.

Instead of reporting:

The patient achieved MCID.

A richer interpretation might be:

The patient exceeded the published threshold for meaningful improvement but remained below the reported PASS value for this population.

That statement distinguishes improvement from final status.

MCID, SCB, and PASS in practice

Consider a patient completing the KOOS, JR. before and after total knee arthroplasty.

Suppose the patient's score increases from 40 before surgery to 64 at follow-up.

That represents a 24-point improvement.

Using the 20-point SCB threshold incorporated into the CMS THA/TKA patient-reported outcome measure, the patient's change would exceed the SCB threshold.¹

But interpretation should not stop there.

The 2026 systematic review identified KOOS, JR. PASS thresholds ranging from approximately 63.7 to 71.0 across included studies.² A score of 64 could therefore meet some published PASS estimates while remaining below others.

That does not mean one threshold is wrong.

It shows why the study population, methodology, and follow-up period matter.

Rather than asking only, "Did the patient improve?", orthopedic outcomes interpretation can consider three related questions:

1. Was the change meaningful?
   MCID helps answer this.

2. Was the improvement substantial?
   SCB raises the threshold.

3. Did the patient reach an acceptable state?
   PASS shifts attention to the outcome the patient ultimately reached.

Together, these measures make it possible to describe an outcome with more precision than a change score alone.

For orthopedic programs increasingly collecting PROMs across surgical episodes, that distinction can also improve how outcomes are discussed with patients, interpreted across populations, and reported in quality programs.

MCID remains an important way to translate changes in outcome scores into clinically meaningful information. But it is only one part of the story. SCB helps identify a larger degree of improvement, while PASS addresses something neither MCID nor SCB can answer: whether the patient has reached a state they find satisfactory.

A patient can improve meaningfully without improving substantially. A patient can improve substantially without reaching an acceptable state. Recognizing those differences provides a more complete way to interpret orthopedic outcomes.

References

¹ Centers for Medicare & Medicaid Services. Clinician-Level and Clinician Group-Level Total Hip Arthroplasty and Total Knee Arthroplasty Patient-Reported Outcome-Based Performance Measures.
https://www.cms.gov/files/document/draft-technical-report.pdf

² Nwachukwu BU, et al. Evaluating Measures of Clinical Meaningfulness for Patient-Reported Outcome Measures in Total Joint Arthroplasty: A Systematic Review. Journal of Arthroplasty. 2026.
https://pubmed.ncbi.nlm.nih.gov/41577304/

³ Migliorini F, et al. Minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient-acceptable symptom state (PASS) in patients who have undergone total knee arthroplasty: a systematic review. 2024.
https://pubmed.ncbi.nlm.nih.gov/38212863/

⁴ Centers for Medicare & Medicaid Services. Patient-Reported Outcomes: Hip/Knee Replacement.
https://data.cms.gov/provider-data/topics/hospitals/patient-reported-outcomes