O’Brien’s Active Compression Test

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 3 min read

Patient Tools

Read, save, and share this guide

Use these quick tools to make this medical article easier to read, print, save, or share with a family member.

Article Summary

O'Brien's Active Compression Test is to indicate potential labral (SLAP Lesion) or acromioclavicular lesions as a cause of shoulder pain. O'Brien's active compression test was primarily developed for the assessment of Acromioclavicular joint pathology following a patient's demonstration of what reproduced their shoulder pain. O'Brien noted in a series of patients it was also excellent for detecting labral pathology. Test The patient is instructed to...

Before reading

RX Patient Tools

Use these quick guides before reading the article, or return to them when you need help preparing questions for a doctor.

Start here Choose the right pathway for symptoms, reports, medicines, or urgent warning signs. Disease article roadmap Read this topic step by step: meaning, symptoms, warning signs, diagnosis, treatment, prevention, and follow-up. Treatment planner Prepare questions about treatment choices, benefits, risks, side effects, and follow-up. Family & caregiver guide Organize symptoms, reports, medicines, questions, and follow-up safely. Nutrition & diet guide Prepare food, hydration, supplement, and medicine-timing questions safely. Prevention guide Organize risk factors, protective habits, screening, and warning signs. Recovery guide Prepare a safe plan for activity, rehabilitation, warning signs, and follow-up.

Educational health guideWritten for patient understanding and clinical awareness.

Reviewed content workflowUse writer and reviewer profiles for stronger trust.

Emergency safety firstUrgent warning signs are highlighted below.

Definition

O’Brien’s Active Compression Test is to indicate potential labral (SLAP Lesion) or acromioclavicular lesions as a cause of shoulder pain. O’Brien’s active compression test was primarily developed for the assessment of Acromioclavicular joint pathology following a patient’s demonstration of what reproduced their shoulder pain. O’Brien noted in a series of patients it was also excellent for detecting labral pathology.

Test

The patient is instructed to flex their arm to 90° with the elbow fully extended and then adduct the arm 10-15°medial to the sagittal plane. The arm is then maximally internally rotated and the patient resists the examiner’s downward force. The procedure is repeated in supination. The O’Brien Test is designed to maximally load and compress the ACJ and superior labrum. For maximal results, the authors stress that the patient should resist the examiner’s downward force rather than the examiner resisting forward flexion.

Positive

Pain elicited by the fIrst maneuver is reduced or eliminated by a second.

ACJ pain =ACJ
Pain or clicking deep in the GHJ = labral

Arthroscopy revealed that the test position (90° forward flexion, 10-15° adduction, and maximum internal rotation) displaces the biceps tendon medially and inferiorly, therefore, putting tension on the bicipitallabral complex. A secondary shear is created in the glenoid and labrum. In an unstable SLAP lesion tension from the biceps tendon from this shear, compression from the capsular windup, or both creates an internal mechanical derangement and displacement that accounts for the painful clicking that patients experience. For a positive test, the patient MUST report a significant decrease in symptomology in the supination test position. Cadaver studies (Parentis et al 2004) have clarified contact between the lesser tuberosity, subscapularis tendon, and superior aspect of the glenoid and labrum in the internally rotated position.

Cadaver studies examined the anatomical basis of the ACJ component of the test. They revealed that the highest compressive pressure was generated in the test position. The greater tuberosity elevates the relatively depressed acromion and locks and loads the ACJ. Full supination relaxed the joint by virtue of the greater tuberosity moving out of the way.

The following results are based on O’Brien’s prospective study of 268 patients.

	Sensitivity	Specificity	NPV
Labral	100%	98.5%	100%
ACJ	100%	96.6%	100%

Research

Compared to:

	Sensitivity	Specificity	NPV
Stetson (2002)	54%	31%	50%!
Guanche (2003) (For Labral)	63%	73%
Chronopoulos E(2004) (For ACJ)	41%	95%	>94%

References

Safety note: This is not a prescription or diagnosis. For severe symptoms, pregnancy danger signs, children with serious illness, chest pain, breathing difficulty, stroke-like weakness, or major injury, seek urgent care.

Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

Write when the problem started and how it changed.
Bring old prescriptions, investigation reports, and current medicines.
Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

What is the most likely cause of my symptoms?
Which danger signs mean I should go to hospital quickly?
Which tests are necessary now, and which can wait?
How should I take medicines safely and what side effects should I watch for?
When should I come for follow-up?

Tests to discuss

Vital signs: temperature, pulse, blood pressure, oxygen saturation
Basic physical examination by a clinician
CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

Rest, drink safe water, and observe symptoms carefully.
Keep a written note of symptoms, duration, temperature, medicines already taken, and allergy history.
Seek medical care quickly if symptoms are severe, worsening, or unusual for the patient.

OTC medicine safety

For mild pain or fever, ask a registered pharmacist or doctor before using common over-the-counter pain/fever medicines.
Do not combine multiple pain medicines without advice, especially if you have kidney disease, liver disease, stomach ulcer, asthma, pregnancy, or take blood thinners.
Do not give adult medicines to children unless a qualified clinician advises it.

Avoid these mistakes

Do not start antibiotics without a proper medical decision.
Do not use steroid tablets or injections casually for quick relief.
Do not delay emergency care because of home remedies.

Get urgent help if

Severe symptoms, confusion, fainting, breathing difficulty, chest pain, severe dehydration, or sudden weakness need urgent medical care.

Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

For rural patients and family caregivers

Patient health record and symptom diary

Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Doctor / qualified healthcare provider

Tests to discuss with doctor

Basic vital signs: temperature, pulse, blood pressure, oxygen level if needed
Relevant blood, urine, imaging, or specialist tests only after clinical assessment

Questions to ask

What is the most likely cause of my symptoms?
Which warning signs mean I should go to emergency care?
Which tests are really needed now?
Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Go to emergency care if you notice:

Severe or rapidly worsening symptoms
Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration

Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.

Step 1
Check danger signs first

If danger signs are present, seek emergency care and do not wait for online information.
Step 2
Record the symptom story

Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.
Step 3
Visit a qualified clinician

A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.
Step 4
Do only useful tests

Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.
Step 5
Follow up and return early if worse

If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips

Take a written symptom diary and all previous prescriptions/test reports.
Do not hide medicines already taken, even herbal or over-the-counter medicines.
Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.

Internal learning pathway

Explore related RX articles

Related guides from RX Harun are grouped to help readers move from overview to symptoms, tests, treatment, and safe next steps.

Rx Physiotherapy (A - Z)

Phone Addiction DefinitionPhone addiction is a type of behavioral addiction indicated by the compulsive use of a smartphone…
Multiple Environment Adaptation Problem DefinitionOur bodies are designed to adapt to changes. Whether it’s a sudden shift in temperature, new…
Escalating Internet Pornography Addiction DefinitionInternet pornography addiction, also known as compulsive pornography consumption, is a condition where individuals develop an…
Spiritual Sex Addiction DefinitionSpiritual sex addiction is a complex issue that can significantly impact individuals’ lives. In simple terms,…
Kundalini Yoga DefinitionKundalini yoga involves various spiritual practices like chanting, breathing, and physical movements. This yoga activates your…
Zero Balancing DefinitionZero Balancing, often abbreviated as ZB, is a holistic body-mind therapy that aims to promote balance…

Read, save, and share this guide

Article Summary

RX Patient Tools