Patient-reported outcome measure
Marx Calculator
Marx Activity Rating Scale
The Marx Activity Rating Scale measures how frequently a patient runs, cuts, decelerates and pivots in their healthiest state over the past year, scoring each on a 0 to 4 frequency scale for a total of 0 to 16, where a higher score means a more demanding activity level.
What the Marx score means
Marx scores run from 0 to 16, where a higher score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- Low activity0–3
Little or no participation in running or cutting sports.
- Moderate activity4–7
Occasional participation in pivoting activity.
- High activity8–11
Regular participation in running and cutting sport.
- Very high activity12–16
Frequent participation across all four activities, typical of competitive athletes.
Clinically important thresholds
A change in score only matters if it exceeds the smallest difference patients actually notice. Every threshold below is reported with the population it was derived in — a threshold quoted without its population is not usable.
| Type | Value | Subscale | Population | Follow-up | Source |
|---|---|---|---|---|---|
| Criterion | ≥ 12 commonly used to define a high-demand athlete | — | ACL reconstruction cohorts | — | Marx RG 2001 |
| MDC | 4.4 points | — | Patients with knee disorders | — | Marx RG 2001 |
MCID is the smallest change a patient perceives as meaningful. PASS is the score above which patients consider their state acceptable. SCB is a substantial rather than minimal benefit. MDC is the smallest change exceeding measurement error. Criterion is a published cut-off, definition or performance figure belonging to a classification or decision rule — it is not a change score and should not be read as one.
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
Each of the four activities — running, cutting, decelerating and pivoting — is scored from 0 (less than one time in a month) to 4 (four or more times in a week), reflecting frequency in the patient’s healthiest and most active state during the past year. The Marx score is the simple sum of the four item scores, giving a total from 0 to 16. The scale measures activity level rather than symptoms, so a higher score indicates greater demand on the knee, not a better knee.
Missing data
All four items are required. The developers published no substitution rule, and with only four items a prorated total would be unreliable.
Instrument profile
- Developer
- Robert G. Marx and colleagues
- Institution
- Hospital for Special Surgery, New York
- First published
- 2001
- Items
- 4
- Response format
- 5-point frequency scale, scored 0–4
- Score range
- 0 to 16
- Direction
- Higher score = better
- Recall period
- The past year, in the patient’s healthiest and most active state
- Completion time
- About 2 minutes
- Age range
- Adults and adolescents
- Regions
- Knee
- Conditions
- ACL injury, Meniscal injury, Knee instability, Post-operative knee rehabilitation
- Procedures
- ACL reconstruction, Meniscal repair, Cartilage repair
- Languages
- English, Spanish, German, Dutch, Portuguese
- Test–retest (ICC)
- 0.97
- Internal consistency
- Cronbach's alpha 0.88
- Validity
- Correlates well with the Tegner activity scale and with the IKDC activity grading, while being quicker to administer and free of the sport-specific ladder that makes Tegner hard to apply outside its original context.
- Responsiveness
- Not intended to change with treatment. It is an exposure and case-mix variable, and a change in Marx score usually reflects a change in lifestyle rather than in knee status.
Normative values
Reference values from published cohorts, for comparison against the score you calculated.
| Population | Age | Mean | SD |
|---|---|---|---|
| Healthy young athletes | — | 12–16 | — |
| General adult population aged 18–54 | — | 5–8 | — |
| Adults over 55 | — | 0–4 | — |
When to use the Marx
Well suited to
- Characterising activity level alongside a symptom score such as the KOOS or IKDC, so that outcomes can be compared between patients of similar demand.
- Stratifying or matching patients in ACL reconstruction research, where activity level strongly predicts re-injury.
- When the Tegner scale’s occupation-and-sport ladder does not fit the patient population.
Limitations and poor fits
- As an outcome measure — it is not designed to improve with treatment and should never be reported as a treatment effect.
- In populations where running and pivoting are not the relevant demands, such as elderly arthroplasty patients, where most will score 0.
- As a substitute for a symptom or function score.
Marx compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| Tegner | 1 | 0–10 | The Tegner Activity Scale is a single-item ordinal ladder that grades a patient's work and sport activity from 0 (sick leave or disability pension because of knee problems) to 10 (national or international elite competitive sport), and is normally recorded twice — the pre-injury level and the current level — so that the drop between them can be reported. |
| Lysholm | 8 | 0–100 | The Lysholm Knee Scoring Scale is an eight-domain questionnaire that rates knee symptoms and function — limp, support, locking, instability, pain, swelling, stair climbing and squatting — on a 0 to 100 scale, where 95 and above is graded excellent, 84 to 94 good, 65 to 83 fair, and below 65 poor. |
| KOOS | 42 | 0–100 | The KOOS is a 42-item patient-reported questionnaire that scores knee function as five separate subscales — Symptoms, Pain, Activities of Daily Living, Sport and Recreation, and Quality of Life — each from 0 (extreme problems) to 100 (no problems). |
| IKDC | 18 | 0–100 | The IKDC Subjective Knee Evaluation Form is an 18-item patient-reported questionnaire covering knee symptoms, sports and daily activity and current knee function, whose raw total is transformed to a 0 to 100 score where 100 means no symptoms and no activity limitation — it requires permission from the AOSSM, so the items are not reproduced here. |
Copyright and permitted use
Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.
The Marx Activity Rating Scale was published in full in the American Journal of Sports Medicine in 2001 and is reproduced freely in clinical practice and research. No licensing programme is operated for it.
References
- Marx RG, Stump TJ, Jones EC, Wickiewicz TL, Warren RF. Development and evaluation of an activity rating scale for disorders of the knee. American Journal of Sports Medicine. 2001.PMID 11394602
- Marx RG. Knee rating scales. Arthroscopy. 2003.PMID 14608329
Editorial status
Not yet reviewedQueued for clinical review by Sam Tuffun, PT, DPT. Sign-off has not taken place — this is a placeholder assignment, not a completed review.