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A patient undergoes anterior approach total hip arthroplasty. Which hip precaution is uniquely required compared to the posterior approach?

Avoid hip internal rotation

Avoid hip adduction past midline

Avoid hip extension and external rotation

Avoid hip flexion greater than 90°

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ONCB ONP-C Orthopaedic Nurse Practitioner Certified

Practice Questions100 questions

2026 Statistics

Key Facts: ONC Exam

150

Total Questions

135 scored

Passing Raw Score

of 135 scored questions

3 hrs

Exam Time

ONCB

34%

Degenerative Disorders

Largest condition domain

$325-450

Exam Fee

ONCB 2026

5 years

Certification Valid

Recertification cycle

The ONC exam has 150 questions (135 scored) with a passing raw score of 97. Content spans degenerative disorders (largest domain), trauma, sports injuries, metabolic bone disease, and pediatric orthopaedics. Eligibility requires 1,000 orthopaedic nursing hours within 3 years. Exam is administered by Meazure Learning. Certification is valid 5 years with renewal via CE or re-exam.

Sample ONC Practice Questions

Try these sample questions to test your ONC exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which structure is the primary weight-bearing joint in the lower extremity?

A.Hip joint

B.Knee joint

C.Ankle joint

D.Subtalar joint

Explanation: The knee joint bears the greatest compressive forces during ambulation, making it the primary weight-bearing joint.

2A patient 6 hours post-total hip arthroplasty (posterior approach) reports severe hip pain and an inability to bear weight. Assessment reveals the affected leg is shortened and internally rotated. What is the priority intervention?

A.Administer prescribed analgesics and reassess

B.Notify the surgeon immediately for suspected dislocation

C.Reposition the patient with abduction pillow and monitor

D.Obtain an X-ray per standing nursing orders

Explanation: Shortening and internal rotation after posterior THA indicate hip dislocation — a surgical emergency requiring immediate surgeon notification.

3Following posterior total hip arthroplasty, which set of movements must the patient avoid to prevent dislocation?

A.Hip extension, abduction, and external rotation

B.Hip flexion >90°, adduction past midline, and internal rotation

C.Hip flexion <45°, abduction, and external rotation

D.Hip extension, adduction past midline, and external rotation

Explanation: Posterior approach hip precautions prohibit flexion >90°, adduction past midline, and internal rotation to protect the posterior capsule repair.

4A patient undergoes anterior approach total hip arthroplasty. Which hip precaution is uniquely required compared to the posterior approach?

A.Avoid hip flexion greater than 90°

B.Avoid hip adduction past midline

C.Avoid hip extension and external rotation

D.Avoid hip internal rotation

Explanation: Anterior approach THA protects the anterior capsule; patients must avoid extension and external rotation rather than the flexion/internal-rotation restrictions of the posterior approach.

5Which DEXA scan T-score value meets the WHO definition of osteoporosis?

A.-1.0 or above

B.Between -1.0 and -2.5

C.-2.5 or below

D.-3.0 or below only

Explanation: The WHO defines osteoporosis as a T-score of -2.5 or below at the femoral neck or lumbar spine on DEXA.

6A patient starting oral bisphosphonate therapy for osteoporosis asks about administration instructions. What is the most important teaching point?

A.Take with a full glass of milk for calcium absorption

B.Remain upright for at least 30 minutes after taking the medication

C.Take at bedtime to reduce GI side effects

D.Crush the tablet and mix with juice if swallowing is difficult

Explanation: Oral bisphosphonates must be taken with plain water and the patient must remain upright for ≥30 minutes to prevent esophageal irritation and pill-induced esophagitis.

7A 72-year-old female has a Z-score of -2.3 on DEXA. What does this finding indicate?

A.Bone density appropriate for her age

B.Bone density lower than expected for her age

C.Bone density higher than expected for her age

D.Severe osteoporosis requiring immediate pharmacotherapy

Explanation: Z-score compares bone density to age-matched peers; a Z-score of -2.3 means bone density is lower than expected for her age, warranting further evaluation for secondary causes.

8A patient in a long leg cast develops the 5 P's of compartment syndrome. Which sign is considered the earliest and most reliable indicator?

A.Pulselessness

B.Pallor

C.Pain with passive stretch

D.Paresthesia

Explanation: Pain with passive stretch of muscles within the compartment is the earliest and most sensitive sign of acute compartment syndrome.

9Which intervention is the priority for a patient with acute compartment syndrome confirmed by intracompartmental pressure measurement?

A.Elevate the extremity above heart level

B.Apply ice packs to the affected limb

C.Prepare the patient for emergent fasciotomy

D.Administer IV mannitol and monitor diuresis

Explanation: Fasciotomy is the definitive treatment for acute compartment syndrome; delay leads to permanent muscle and nerve necrosis.

10A nurse performs neurovascular checks on a patient with a new below-knee cast. Which assessment is the most important to include?

A.Skin color and temperature proximal to the cast

B.Capillary refill, sensation, and movement of toes

C.Pain level using the numeric rating scale

D.Edema measurement at the cast edges

Explanation: Capillary refill, sensation, and movement of digits distal to the cast assess circulation, nerve function, and motor status — the core neurovascular triad.

About the ONC Exam

The ONC (Orthopaedic Nurse Certified) validates specialized knowledge in orthopaedic nursing. The exam contains 150 items (135 scored, 15 unscored pilot) and tests two overlapping specification axes: musculoskeletal conditions (degenerative 34%, trauma 17%, sports 10%, metabolic 8%, inflammatory 7%, congenital/pediatric 5%, tumors 5%, neuromuscular 4%) and nursing tasks (pain management, complications, self-care, activity, nutrition, psychosocial). Eligibility requires a current RN license and 1,000 orthopaedic nursing hours within the past 3 years. Certification is valid for 5 years.

Questions

150 scored questions

Time Limit

3 hours

Passing Score

Raw score 97/135 (approximately 72%)

Exam Fee

$325-450 (Orthopaedic Nurses Certification Board (ONCB) / Meazure Learning)

ONC Exam Content Outline

34%

Degenerative Disorders

Osteoarthritis, rheumatoid arthritis, degenerative disc disease, total hip arthroplasty (anterior/posterior approaches, hip precautions), total knee arthroplasty, total shoulder arthroplasty, periprosthetic joint infection, and post-arthroplasty nursing management

17%

Orthopaedic Trauma

Fracture classification (Salter-Harris, Gustilo-Anderson, Garden), traction (Buck's, skeletal), casting (neurovascular checks, compartment syndrome), ORIF, external fixation, open fractures, pelvic fractures, trauma assessment (ATLS primary survey)

10%

Sports Injuries

Ligament sprains, tendon injuries, meniscal tears, rotator cuff injuries, conservative and surgical management, rehabilitation nursing

Metabolic Bone Disorders

Osteoporosis (DEXA T/Z scores, bisphosphonates, denosumab, teriparatide), Paget's disease, vitamin D deficiency, calcium metabolism, glucocorticoid-induced osteoporosis

Inflammatory Disorders

Rheumatoid arthritis (anti-CCP, methotrexate monitoring), gout (acute vs prophylaxis treatment), septic arthritis, osteomyelitis (organisms, imaging findings, treatment)

Congenital/Pediatric

DDH (ultrasound diagnosis, risk factors), SCFE (obligate external rotation), Legg-Calvé-Perthes (avascular necrosis, prognostic factors), adolescent idiopathic scoliosis (Cobb angle, bracing thresholds)

Musculoskeletal Tumors

Osteosarcoma (sunburst pattern, chemotherapy + limb-salvage), Ewing sarcoma (onion skin pattern, pediatric), chondrosarcoma (adults 50-70), pathological fractures from metastatic disease

Neuromuscular Disorders

Nerve root assessment (L4, L5, S1 dermatomes), post-surgical nerve injury, ankylosing spondylitis perioperative considerations

How to Pass the ONC Exam

What You Need to Know

Passing score: Raw score 97/135 (approximately 72%)
Exam length: 150 questions
Time limit: 3 hours
Exam fee: $325-450

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

ONC Study Tips from Top Performers

1Master posterior THA hip precautions (no flexion >90°, no adduction past midline, no internal rotation) and how they differ from anterior approach

2Know the 5-6 P's of compartment syndrome and understand that pain with passive stretch is the earliest sign

3Understand Buck's traction: skin-based, temporary, and must hang freely — never rest weights on the bed

4Learn DEXA T-score thresholds: normal ≥-1.0, osteopenia -1.0 to -2.5, osteoporosis ≤-2.5

5Review Salter-Harris classification: Type II (physis + metaphysis) is most common; Type V is crush injury diagnosed retrospectively

6Study VTE prophylaxis: AAOS recommends 35 days of prophylaxis after THA; early ambulation and ankle pumps activate the calf pump

7Know fat embolism triad: respiratory distress + mental status change + petechiae at 24-72 hours post long bone fracture

8Understand anti-CCP antibody (~95% specific for RA) vs. elevated ESR/CRP (non-specific inflammatory markers)

9Review pediatric conditions: DDH (ultrasound in infants), LCP (AVN in 4-8 year olds), SCFE (obligate external rotation with hip flexion in overweight adolescents)

10Practice neurovascular check documentation: CMS (circulation, movement, sensation) every 1-2 hours post-operatively

Frequently Asked Questions

What is the ONC exam?

The ONC (Orthopaedic Nurse Certified) is a specialty certification offered by the Orthopaedic Nurses Certification Board (ONCB). It validates advanced knowledge and skills in orthopaedic nursing, including total joint arthroplasty, fracture management, spine surgery, DVT prophylaxis, and musculoskeletal disease management.

What are the ONC eligibility requirements?

To sit for the ONC exam you must: (1) Hold a current, full, and unencumbered RN license in the United States, (2) Have a minimum of 2 years of RN experience, and (3) Have completed at least 1,000 hours of orthopaedic nursing practice within the past 3 years.

How many questions are on the ONC exam?

The ONC exam contains 150 questions total: 135 scored questions and 15 unscored pilot items. Candidates must answer at least 97 of the 135 scored questions correctly to pass. The exam is administered via computer-based testing through Meazure Learning.

What content areas are covered on the ONC exam?

The ONC exam is structured around two axes: musculoskeletal conditions (degenerative disorders 34%, trauma 17%, sports injuries 10%, metabolic disorders 8%, inflammatory disorders 7%, congenital/pediatric 5%, tumors 5%, neuromuscular 4%) and nursing tasks (pain management, complications prevention, self-care, activity, nutrition, psychosocial support).

What is the ONC passing score?

The ONC passing score is a raw score of 97 correct answers out of 135 scored questions. This represents approximately 72% of scored questions answered correctly. ONCB does not publish official first-time pass rate statistics.

How long is ONC certification valid?

ONC certification is valid for 5 years. Recertification can be achieved by earning continuing education units in orthopaedic nursing or by retaking the ONC exam within the renewal window.

How should I prepare for the ONC exam?

Study systematically using the ONCB test blueprint and NAON Core Curriculum for Orthopaedic Nursing. Prioritize high-yield areas: total hip and knee arthroplasty (hip precautions, complications), DVT prophylaxis and anticoagulation, compartment syndrome recognition, pain management (multimodal analgesia, peripheral nerve blocks), metabolic bone disorders (DEXA scoring, bisphosphonates), and pediatric orthopaedic conditions. Allow 8-16 weeks of dedicated preparation.