ONC® EXAM PREP 2026-2027:
Practice Questions & Rationales for
Orthopaedic Nurse Certification
1. A nurse is reviewing the structure of a long bone. Which part of the
bone is responsible for longitudinal growth during childhood?
A) Epiphysis
B) Diaphysis
C) Metaphysis
D) Periosteum
Correct Answer: C) Metaphysis
Rationale: The metaphysis is the region of the bone between the epiphysis
and diaphysis that contains the epiphyseal (growth) plate. This plate is
responsible for longitudinal bone growth during childhood and
adolescence. The epiphysis is the end of the bone, the diaphysis is the shaft,
and the periosteum is the outer membrane covering the bone.
2. A patient asks the nurse about the function of synovial fluid. Which
response is most accurate?
,A) "Synovial fluid provides nutrients to the cartilage and reduces friction
between joints."
B) "Synovial fluid acts as a cushion to absorb shock in weight-bearing
joints."
C) "Synovial fluid helps strengthen ligaments and tendons around the
joint."
D) "Synovial fluid prevents infection by containing immune cells."
Correct Answer: A) "Synovial fluid provides nutrients to the cartilage
and reduces friction between joints."
Rationale: Synovial fluid is a viscous fluid found in synovial joints that
lubricates the joint, reducing friction between articular cartilages, and
provides nutrients to the avascular cartilage through diffusion. While
synovial fluid does provide some shock absorption, its primary functions
are lubrication and nutrition. It does not strengthen ligaments/tendons or
have significant immune function.
3. Which type of joint allows for the greatest range of motion?
A) Hinge joint
B) Pivot joint
C) Ball-and-socket joint
D) Saddle joint
Correct Answer: C) Ball-and-socket joint
Rationale: Ball-and-socket joints (e.g., shoulder and hip) allow movement
in multiple planes including flexion, extension, abduction, adduction,
rotation, and circumduction, providing the greatest range of motion of any
,joint type. Hinge joints (elbow, knee) allow motion in one plane, pivot joints
(proximal radioulnar) allow rotational movement, and saddle joints (thumb)
allow movement in two planes.
4. The nurse is assessing a patient's muscle strength. Which grade
indicates active movement against gravity with full resistance?
A) 2/5
B) 3/5
C) 4/5
D) 5/5
Correct Answer: D) 5/5
Rationale: The muscle strength grading scale (0-5) is standardized: 0/5 =
no contraction, 1/5 = flicker/trace contraction, 2/5 = active movement with
gravity eliminated, 3/5 = active movement against gravity only, 4/5 = active
movement against gravity and some resistance, and 5/5 = active movement
against gravity with full resistance (normal strength).
5. A patient presents with pain and swelling in the knee. During the
assessment, the nurse notes the knee joint is warm to touch and there
is a palpable effusion. Which structure is most likely involved?
A) Meniscus
B) Synovial membrane
C) Ligament
D) Tendon
, Correct Answer: B) Synovial membrane
Rationale: When the synovial membrane becomes inflamed (synovitis), it
produces excess synovial fluid, leading to joint effusion, warmth, and
swelling. This is characteristic of inflammatory joint conditions like
rheumatoid arthritis. Meniscal injuries typically cause mechanical symptoms
like locking or catching. Ligament injuries cause instability, and tendon
injuries cause pain with muscle contraction.
6. The nurse is educating a patient about the importance of vitamin D
for bone health. Which statement accurately describes vitamin D's
role?
A) Vitamin D directly builds bone matrix
B) Vitamin D enhances calcium absorption from the intestines
C) Vitamin D is only obtained through dietary sources
D) Vitamin D prevents bone resorption by osteoclasts
Correct Answer: B) Vitamin D enhances calcium absorption from the
intestines
Rationale: Vitamin D (specifically calcitriol, its active form) promotes
intestinal absorption of calcium and phosphorus, which are essential for
bone mineralization. Vitamin D is obtained through dietary sources and
synthesized in the skin through sun exposure. It does not directly build
bone matrix; osteoblasts perform that function. While vitamin D does
influence bone remodeling, it does not directly prevent bone resorption.
Practice Questions & Rationales for
Orthopaedic Nurse Certification
1. A nurse is reviewing the structure of a long bone. Which part of the
bone is responsible for longitudinal growth during childhood?
A) Epiphysis
B) Diaphysis
C) Metaphysis
D) Periosteum
Correct Answer: C) Metaphysis
Rationale: The metaphysis is the region of the bone between the epiphysis
and diaphysis that contains the epiphyseal (growth) plate. This plate is
responsible for longitudinal bone growth during childhood and
adolescence. The epiphysis is the end of the bone, the diaphysis is the shaft,
and the periosteum is the outer membrane covering the bone.
2. A patient asks the nurse about the function of synovial fluid. Which
response is most accurate?
,A) "Synovial fluid provides nutrients to the cartilage and reduces friction
between joints."
B) "Synovial fluid acts as a cushion to absorb shock in weight-bearing
joints."
C) "Synovial fluid helps strengthen ligaments and tendons around the
joint."
D) "Synovial fluid prevents infection by containing immune cells."
Correct Answer: A) "Synovial fluid provides nutrients to the cartilage
and reduces friction between joints."
Rationale: Synovial fluid is a viscous fluid found in synovial joints that
lubricates the joint, reducing friction between articular cartilages, and
provides nutrients to the avascular cartilage through diffusion. While
synovial fluid does provide some shock absorption, its primary functions
are lubrication and nutrition. It does not strengthen ligaments/tendons or
have significant immune function.
3. Which type of joint allows for the greatest range of motion?
A) Hinge joint
B) Pivot joint
C) Ball-and-socket joint
D) Saddle joint
Correct Answer: C) Ball-and-socket joint
Rationale: Ball-and-socket joints (e.g., shoulder and hip) allow movement
in multiple planes including flexion, extension, abduction, adduction,
rotation, and circumduction, providing the greatest range of motion of any
,joint type. Hinge joints (elbow, knee) allow motion in one plane, pivot joints
(proximal radioulnar) allow rotational movement, and saddle joints (thumb)
allow movement in two planes.
4. The nurse is assessing a patient's muscle strength. Which grade
indicates active movement against gravity with full resistance?
A) 2/5
B) 3/5
C) 4/5
D) 5/5
Correct Answer: D) 5/5
Rationale: The muscle strength grading scale (0-5) is standardized: 0/5 =
no contraction, 1/5 = flicker/trace contraction, 2/5 = active movement with
gravity eliminated, 3/5 = active movement against gravity only, 4/5 = active
movement against gravity and some resistance, and 5/5 = active movement
against gravity with full resistance (normal strength).
5. A patient presents with pain and swelling in the knee. During the
assessment, the nurse notes the knee joint is warm to touch and there
is a palpable effusion. Which structure is most likely involved?
A) Meniscus
B) Synovial membrane
C) Ligament
D) Tendon
, Correct Answer: B) Synovial membrane
Rationale: When the synovial membrane becomes inflamed (synovitis), it
produces excess synovial fluid, leading to joint effusion, warmth, and
swelling. This is characteristic of inflammatory joint conditions like
rheumatoid arthritis. Meniscal injuries typically cause mechanical symptoms
like locking or catching. Ligament injuries cause instability, and tendon
injuries cause pain with muscle contraction.
6. The nurse is educating a patient about the importance of vitamin D
for bone health. Which statement accurately describes vitamin D's
role?
A) Vitamin D directly builds bone matrix
B) Vitamin D enhances calcium absorption from the intestines
C) Vitamin D is only obtained through dietary sources
D) Vitamin D prevents bone resorption by osteoclasts
Correct Answer: B) Vitamin D enhances calcium absorption from the
intestines
Rationale: Vitamin D (specifically calcitriol, its active form) promotes
intestinal absorption of calcium and phosphorus, which are essential for
bone mineralization. Vitamin D is obtained through dietary sources and
synthesized in the skin through sun exposure. It does not directly build
bone matrix; osteoblasts perform that function. While vitamin D does
influence bone remodeling, it does not directly prevent bone resorption.
