Muscle, joint & pain

HOOS Jr. for Hip Replacement Tracking

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Six questions carved out of a forty-question survey, and the trade is deliberate: HOOS Jr. is quick enough for a clinic to collect from everyone, and blunt at the top end. Ceiling effects of 37% to 46% were reported in its validation, meaning a large share of patients land on the maximum score and the scale can no longer tell an excellent result from a perfect one.

Last updated: July 2026

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What does HOOS Jr. ask?

Six questions, and only six. Two ask about hip pain and four about activities of daily living — the ordinary business of rising from a chair, managing stairs, walking 1. There is nothing about sport, nothing about quality of life, and nothing an examination would contribute. The patient fills it in, usually on paper before a clinic visit or through a portal beforehand.

Those six items were not chosen by preference. They were drawn out of the 40-item Hip disability and Osteoarthritis Outcome Score by Rasch-based item reduction applied to cohorts of patients undergoing total hip arthroplasty 1. The parent hoos questionnaire is a five-subscale instrument covering pain, symptoms, daily activities, sport and recreation, and hip-related quality of life, validated in hip osteoarthritis and more responsive than WOMAC on its pain and symptom subscales 2.

HOOS Jr. is not a shortened summary of the HOOS. It is its own instrument, derived from a subset of those questions and scored by its own conversion table.

How six answers become a score out of 100

The six raw answers are summed, and then that sum is converted using a crosswalk table published with the instrument, which maps it onto an interval scale running from 0 to 100. On that scale, 0 represents total hip disability and 100 represents perfect hip health, so a higher number is a better hip 1.

The conversion step is the part that gets skipped. A raw sum is ordinal: the distance between one answer option and the next is not guaranteed to be equal, so the total cannot be treated as a measurement. The crosswalk is what turns it into a number where the gap between 40 and 50 carries the same weight as the gap between 80 and 90 1. Six answers added up and called a HOOS Jr. score is a different number from the one the instrument produces.

Direction is worth stating plainly, because hip scores genuinely disagree about it. On HOOS Jr., rising means improving 1.

The ceiling: when the score runs out of room

Its validation reported ceiling effects of 37% to 46%, alongside floor effects of only 0.6% to 1.9% 1. A ceiling effect is the share of respondents scoring the maximum, beyond which an instrument cannot register any further improvement. In plain terms, somewhere between a third and nearly half of the patients in those cohorts finished at the top of the scale.

This is not a scandal, it is arithmetic. Six questions about pain and basic daily activity set a low bar for a hip replacement that has worked, and standing up from a chair without difficulty is not a demanding test of a new joint.

The practical consequence is worth carrying. Once a score reaches the maximum, a hip that keeps improving — more walking distance, a return to a hobby, the last of a limp — cannot show that as a rising number. A score that stops climbing near the top of the scale is usually the instrument running out of room, not a recovery that has stalled. The very small floor effects mean the other end behaves better: the scale still separates people who are doing badly from people who are doing very badly.

Is HOOS Jr. sensitive enough to show a replacement working?

On the evidence in its own validation, markedly so. Responsiveness was reported as standardized response means of 2.38 and 2.03 across its two cohorts, which are large values for a patient-reported measure. Internal consistency was high, with Person Separation Indices of 0.86 and 0.87, and the score correlated moderately to excellently with other hip surveys, at Spearman's rho of 0.60 to 0.94 1.

What that validation did not produce is a change threshold. The paper reports no minimal clinically important difference and no minimal detectable change 1. There is no figure in it saying that a 12-point rise is meaningful while an 8-point rise is not, and any such number quoted for HOOS Jr. has come from separate, later work.

That gap is easy to read as an oversight. It is closer to restraint. A change threshold has to be anchored against something outside the instrument, and this paper set out to build the scale and demonstrate that it moves, not to calibrate what its movements are worth.

How HOOS Jr. compares with the other hip and knee scores

Several scores are in circulation, and they share neither a scale, a scorer, nor reliably a direction. koos jr. is the knee counterpart from the same 2016 work: seven items, an interval score from 0 to 100, where 0 is complete knee disability and 100 is perfect knee health 3.

The Harris Hip Score is much older and clinician-administered — 100 points divided across pain (44), functional capacity (47), range of motion (5) and absence of deformity (4), with higher totals meaning a better hip 4. That one is not a patient-reported measure at all; someone has to examine the hip to complete it.

The oxford hip score is the trap worth knowing about. It is a 12-item patient-completed questionnaire, developed and validated in 220 patients assessed before surgery and again at six months, with good internal consistency and sensitivity to clinically important change 5. Its original scoring sums the twelve items to a total between 12 and 60, in which lower is better. The widely used 0-to-48 version, in which higher is better, is a later recoding 5. Same instrument name, opposite directions.

Before setting two hip scores side by side, it is worth confirming which instrument, which version, and which direction — the same numeral can describe an excellent hip or a failing one.

What the score does not decide

HOOS Jr. does not decide whether to have a hip replacement. It was derived and validated in patients already undergoing total hip arthroplasty, and its paper does not establish how the instrument performs in people who are not having that operation 1. No score marks the point at which surgery becomes the right answer.

Hip replacement indications rest on a different set of inputs. The orthopaedic guideline for hip osteoarthritis covers nonsurgical management — exercise and physical therapy, anti-inflammatory medication — alongside surgical options 6, and which of those fits a particular person depends on their symptoms, their imaging, what has already been tried and for how long, their other medical conditions, and what they want the hip to be able to do. For someone whose arthritis has stopped responding to nonsurgical care, replacement is among the options that guideline addresses, and a low questionnaire score is neither the reason to proceed nor a reason to wait.

Where the six questions earn their place is on either side of that decision: a baseline recorded before surgery, and the same questions afterwards, so that improvement is measured rather than remembered.

Reading your own HOOS Jr. over time

The score exists to be compared with itself. A number recorded before surgery, then the same six questions at a few months, at a year, and later, makes a line — and the line is what a surgeon's office or a joint registry is actually reading 1.

Three things make that line easier to read. The pre-operative baseline is the most valuable single measurement on it, because without one the post-operative number has nothing to be better than. The spacing matters as well: hip replacement recovery timeline expectations run on weeks, while these scores are collected at set intervals, so the questionnaire is a series of stills rather than a film. And the top of the scale is crowded, which means a score that stops rising in the nineties is describing the instrument more than the hip.

What the six questions cannot see deserves naming too. They ask about pain and basic daily activity. They do not ask about a limp, about sleeping on that side, about confidence on a kerb, or about the one thing a person most wants back. Those belong in the conversation whatever the number says.

Common questions

There is no published banding that sorts scores into good, fair and poor. The scale runs from 0, meaning total hip disability, to 100, meaning perfect hip health, and higher is better. Beyond that, the number is read against your own earlier scores rather than against a cutoff, which is why a baseline before surgery is so useful.

Its validation paper reports no minimal clinically important difference and no minimal detectable change, so there is no threshold from that source. Any figure quoted comes from later research. In practice, surgeons read the size of the change from the pre-operative baseline together with what the person can now do, rather than grading a point difference.

No. The HOOS has 40 items across five subscales, including sport and recreation and hip-related quality of life. HOOS Jr. has six items drawn only from pain and daily activities, converted to its own 0-to-100 scale. The two produce different numbers and are not interchangeable, so a score from one should not be entered as a score on the other.

It cannot. The instrument was derived and validated in people already having a total hip replacement, and its paper does not establish how it behaves in anyone else. There is no score at which an operation becomes indicated. That decision draws on symptoms, imaging, what has already been tried, other health conditions, and personal priorities.

Because they are different instruments with different scales, and sometimes with opposite directions. On HOOS Jr., higher is better. The Oxford Hip Score exists in an original version where lower is better and a later recoded version where higher is better. The Harris Hip Score is completed by a clinician after examining the hip, not by the patient.

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After hip surgery, symptoms that do not wait for the next questionnaire

  • —New calf pain, swelling or warmth in the operated leg, particularly alongside chest pain or sudden breathlessness
  • —Increasing redness, drainage or a foul smell from the surgical wound, or a fever developing after the first few days
  • —A sudden pop with severe pain and inability to bear weight, or a leg that suddenly looks shorter or turned in or out compared with the other one
  • —Pain that had been settling and then sharply worsens, especially after a fall or a twist

Sudden breathlessness or chest pain alongside a swollen, painful calf is an emergency — call 911. A hip that gives way with severe pain, or a leg that suddenly looks shortened or rotated, needs the emergency department the same day.

This page explains what a hip questionnaire measures and what it leaves out. It is health information, not medical advice. No score can examine a hip or judge whether surgery is right for you; that belongs with the clinician looking after you.

References

  1. 1.Lyman S, Lee YY, Franklin PD, et al. (2016). Validation of the HOOS, JR: A Short-form Hip Replacement Survey. Clinical Orthopaedics and Related Research, 474(6):1472-1482. doi:10.1007/s11999-016-4718-2 ✓That HOOS Jr. is a six-item short form of the 40-item HOOS, derived by Rasch-based item reduction in total hip arthroplasty cohorts, comprising 2 pain items and 4 activities-of-daily-living items; that a crosswalk table converts the raw sum to an interval score from 0 (total hip disability) to 100 (perfect hip health), higher being better; its internal consistency (Person Separation Index 0.86 and 0.87), external validity against other hip surveys (Spearman's rho 0.60-0.94), responsiveness (standardized response means 2.38 and 2.03), and floor (0.6%-1.9%) and ceiling (37%-46%) effects; that it reports no MCID or MDC; and that its scope is limited to patients undergoing total hip arthroplasty.
  2. 2.Nilsdotter AK, Lohmander LS, Klässbo M, Roos EM (2003). Hip disability and osteoarthritis outcome score (HOOS)—validity and responsiveness in total hip replacement. BMC Musculoskeletal Disorders. PMID 12777182 ✓That the parent HOOS is a patient-reported outcome with five subscales (pain, symptoms, activities of daily living, sport and recreation, hip-related quality of life) validated for hip osteoarthritis, and more responsive than WOMAC on its pain and symptom subscales.
  3. 3.Lyman S, Lee YY, Franklin PD, Li W, Cross MB, Padgett DE (2016). Validation of the KOOS, JR: A Short-form Knee Arthroplasty Outcomes Survey. Clinical Orthopaedics and Related Research, 474(6):1461-1471. doi:10.1007/s11999-016-4719-1 ✓That the KOOS, JR is a seven-item knee instrument scored on an interval scale from 0 (complete knee disability) to 100 (perfect knee health), with higher scores meaning better knee health.
  4. 4.Harris WH (1969). Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am. doi:10.2106/00004623-196951040-00012 ✓That the Harris Hip Score is a clinician-administered 100-point scale weighted across pain (44 points), functional capacity (47), range of motion (5) and absence of deformity (4), scored so that higher totals indicate a better hip.
  5. 5.Dawson J, Fitzpatrick R, Carr A, Murray D. (1996). Questionnaire on the perceptions of patients about total hip replacement. J Bone Joint Surg Br. 1996;78(2):185-90. doi:10.1302/0301-620X.78B2.0780185 ✓That the Oxford Hip Score is a 12-item patient-completed questionnaire developed and validated in 220 patients assessed before surgery and at six months, with high internal consistency and sensitivity to clinically important change; and that its original scoring sums twelve items to 12-60 with lower being better, the 0-48 higher-is-better metric being a later recoding.
  6. 6.American Academy of Orthopaedic Surgeons (AAOS) (2023). Management of Osteoarthritis of the Hip — Clinical Practice Guideline. AAOS. link ✓That the orthopaedic guideline for hip osteoarthritis addresses nonsurgical management, including exercise and physical therapy and anti-inflammatory medication, alongside surgical options.

6 sources, numbered by first appearance. General health information, not medical advice. AI-assisted editorial content — every citation independently verified. Editorial policy

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