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HLT-PHYS81-02 · Lesson 4 · 14 clock hours · theory

Kinesiology: Planes, Axes, and Joint Motion

Objective. Students correctly classify movements of all major joints into the appropriate plane and axis, and use a goniometer to measure and record range of motion at the shoulder, elbow, hip, and knee within accepted clinical norms, demonstrating correct technique on at least 4 of 5 measurements.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed clinician in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

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Planes, Axes, and Joint Motion

Understanding how the body moves is the foundation of physical therapy aide work. Before you can assist a patient with exercise, observe movement quality, or record range-of-motion measurements, you need a shared language for describing motion. That language is built on three reference planes, three axes of rotation, and a set of directional movement terms.

The Anatomical Position

All movement descriptions start from the anatomical position: the person is standing upright, feet together, palms facing forward, eyes looking straight ahead. Every plane and axis is defined relative to this position, regardless of how the patient is actually lying or sitting when you assess them.

The Three Planes of the Body

Sagittal plane — an imaginary vertical slice that divides the body into left and right halves. Movements occurring in this plane travel forward and backward. Examples: shoulder flexion and extension, elbow flexion and extension, hip flexion and extension, knee flexion and extension, and ankle dorsiflexion and plantarflexion.

Frontal plane (coronal plane) — a vertical slice that divides the body into front and back halves. Movements in this plane travel side to side. Examples: shoulder abduction and adduction, hip abduction and adduction, lateral trunk flexion, and wrist radial and ulnar deviation.

Transverse plane (horizontal plane) — a horizontal slice that divides the body into upper and lower halves. Movements in this plane involve rotation. Examples: shoulder internal and external rotation, hip internal and external rotation, cervical rotation, and forearm pronation and supination.

The Three Axes of Rotation

Every planar movement rotates around a corresponding axis — a line through the joint center perpendicular to that plane.

A helpful memory cue: the axis is always perpendicular to its corresponding plane.

Key Movement Terms

| Term | Meaning |

|---|---|

| Flexion | Decreasing the angle between body segments |

| Extension | Increasing the angle between body segments |

| Abduction | Moving away from the midline |

| Adduction | Moving toward the midline |

| Internal rotation | Rotating the anterior surface toward the midline |

| External rotation | Rotating the anterior surface away from the midline |

| Pronation / Supination | Forearm rotation; palm down / palm up |

| Dorsiflexion / Plantarflexion | Ankle: toes up / toes down |

Using a Goniometer

A goniometer is a protractor-like instrument used to measure joint angles and therefore range of motion (ROM). The standard plastic goniometer has a stationary arm, a movable arm, and a fulcrum (pivot point). Angles are read in degrees from 0° to 180° on most models.

General technique — always follow APTA-aligned guidelines:

1. Explain the procedure to the patient and obtain consent.

2. Position the patient consistently (supine, sitting, or prone as required by the joint being measured).

3. Identify and palpate the bony landmarks that define the joint center and the long axes of both body segments.

4. Align the fulcrum over the joint center.

5. Align the stationary arm with the proximal segment; align the movable arm with the distal segment.

6. Move the joint passively (or guide active motion) to the end of available range, stopping before pain or tissue resistance.

7. Read and record the angle in degrees. Note whether the measurement is active ROM (AROM) or passive ROM (PROM).

Landmark guide for the four joints you will measure:

Safety and Scope of Practice

As a PT aide, you assist and document under the direct supervision of a licensed physical therapist (PT) or physical therapist assistant (PTA). You do not interpret findings, diagnose, or adjust a treatment plan. Stop any measurement immediately if the patient reports pain, dizziness, or discomfort, and notify the supervising clinician. Never force a joint beyond its comfortable end range. Confirm with your supervisor before measuring any joint that is post-surgical, acutely injured, or where precautions are in place.

Why This Matters in the Clinic

Accurate ROM measurements allow the PT to set a baseline, track progress, and adjust the plan of care. Consistent goniometer technique — same landmarks, same patient position, same arm alignment every time — produces reliable data. Small errors in landmark identification or arm alignment can shift readings by several degrees, which can mislead clinical decision-making. Practice until your technique is automatic.

Key terms10

Anatomical positionThe standard reference posture: upright, feet together, palms facing forward; all planes and movement terms are defined relative to this position.
Sagittal planeThe vertical plane dividing the body into left and right halves; movements in this plane include flexion and extension.
Frontal (coronal) planeThe vertical plane dividing the body into front and back halves; movements in this plane include abduction and adduction.
Transverse (horizontal) planeThe horizontal plane dividing the body into upper and lower halves; movements in this plane involve rotation.
Axis of rotationAn imaginary line through a joint center, perpendicular to the plane of movement, around which a segment rotates.
GoniometerA protractor-like instrument with a stationary arm, movable arm, and fulcrum used to measure joint angles in degrees.
Range of motion (ROM)The arc of movement available at a joint, measured in degrees; may be active (AROM, patient moves independently) or passive (PROM, clinician moves the segment).
AbductionMovement of a body segment away from the midline of the body, occurring in the frontal plane.
FulcrumThe pivot point of a goniometer, placed over the joint center during measurement.
Scope of practiceThe defined boundaries of tasks a PT aide is legally and professionally permitted to perform, always under PT or PTA supervision; aides assist and document but do not evaluate or interpret clinical findings.

Worked examples4

1. You are measuring shoulder flexion with a goniometer. After moving the patient's arm into full available flexion, you read the movable arm at 165°. Published normal shoulder flexion is approximately 180°. What does this tell you, and how do you record it?
  1. Step 1 — Confirm your starting (zero) position: in anatomical position, the arm hangs at the side and the goniometer should read 0° before movement begins.
  2. Step 2 — Read the movable arm at the end of available passive range: you noted 165°.
  3. Step 3 — Compare to a published normal value: normal shoulder flexion is commonly cited as approximately 180°.
  4. Step 4 — Calculate the deficit: 180° − 165° = 15° short of full normal range.
  5. Step 5 — Record the finding accurately on the ROM data form: 'Left/Right shoulder flexion PROM = 165°' (note active or passive, patient position, and date). Do not label it 'limited' in the chart — that interpretation belongs to the PT.
Answer: Record shoulder flexion PROM as 165°. The measurement is 15° less than the commonly accepted normal of approximately 180°. Document the number and conditions; the supervising PT interprets clinical significance.
2. During elbow flexion measurement, your goniometer reads 140° on the first trial and 128° on the second trial of the same arm in the same session. What is the most likely source of error, and how do you correct it?
  1. Step 1 — Identify possible sources of variability: landmark placement, fulcrum alignment over the lateral epicondyle, arm alignment along the humerus and forearm, and patient positioning can all shift readings.
  2. Step 2 — Check landmark re-palpation: if the fulcrum moves slightly between trials, the angle reading changes. Re-palpate the lateral epicondyle carefully before each measurement.
  3. Step 3 — Check patient position: ensure the patient is in the same starting position (e.g., supine, arm at side, forearm supinated) for both trials.
  4. Step 4 — Re-align the movable arm: ensure it tracks along the lateral forearm toward the radial styloid consistently.
  5. Step 5 — Take a third measurement after correcting technique, then record all values or an average per your facility's protocol.
Answer: A 12° difference between trials indicates inconsistent landmark identification or arm alignment. Re-palpate the lateral epicondyle, maintain consistent patient positioning, and re-measure. Reliable technique requires the same landmarks, position, and arm alignment every time.
3. A classmate states: 'Hip abduction occurs in the sagittal plane around the mediolateral axis.' Identify the errors and state the correct plane and axis.
  1. Step 1 — Define hip abduction: movement of the thigh away from the body's midline, traveling to the side.
  2. Step 2 — Match the movement direction to a plane: side-to-side movements occur in the frontal (coronal) plane, not the sagittal plane.
  3. Step 3 — Identify the corresponding axis: the frontal plane rotates around the anteroposterior (sagittal) axis, not the mediolateral axis.
  4. Step 4 — State the correction clearly.
Answer: Hip abduction occurs in the FRONTAL (coronal) plane around the ANTEROPOSTERIOR (sagittal) axis. The sagittal plane governs forward-and-backward movements such as hip flexion and extension.
4. You measure knee flexion PROM on a patient and record 95°. The patient's status goal is to reach 120° of knee flexion for stair climbing. How many degrees of additional flexion does the patient need to reach the goal?
  1. Step 1 — Identify the current measurement: 95° of knee flexion PROM.
  2. Step 2 — Identify the goal: 120° of knee flexion.
  3. Step 3 — Subtract current from goal: 120° − 95° = 25°.
  4. Step 4 — Record and report the difference to the supervising PT; you are documenting, not setting or modifying the goal.
Answer: The patient needs 25° of additional knee flexion to reach the 120° goal. Document the current measurement and report it to the supervising PT.
In class: Plane and axis lecture with 3-D plane model: instructor uses a transparent cube model and volunteers to show flexion/extension in the sagittal plane, abduction/adduction in the frontal plane, and rotation in the transverse plane; students complete a movement classification worksheet. · Goniometer introduction: instructor demonstrates standard goniometer placement per APTA guidelines for shoulder flexion, elbow flexion, hip flexion, and knee flexion/extension; students practice in pairs on a therapy table, recording measurements on a ROM data form and comparing to published normal values. · Video analysis activity: students watch two short video clips of a patient performing a sit-to-stand transfer and a reaching task; they document which joints are moving, in which plane, and estimate whether motion appears full, limited, or excessive, then discuss findings with the class.
Materials: Transparent 3-D plane model, standard plastic goniometers (one per pair), ROM data forms, therapy tables, laptop/projector for video clips, APTA Guide to Physical Therapist Practice (reference for normal ROM values), movement classification worksheet
Check: Students perform 5 goniometric measurements on a partner; pass is correct technique and recording on at least 4 of 5 (per instructor checklist). Movement classification worksheet scored 16/20 (80%) to pass.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Anatomy & Kinesiology
1. A patient performs shoulder abduction, raising the arm out to the side. In which plane and around which axis does this motion occur?
Clinical Skills / ROM Measurement
2. When measuring elbow flexion with a goniometer, where should the fulcrum be placed?
Safety & Scope of Practice
3. During a goniometric measurement, the patient reports sudden sharp pain before the end of available range. What should the PT aide do immediately?
Anatomy & Kinesiology
4. Which of the following movements occurs in the transverse plane?
Clinical Skills / ROM Measurement
5. A PT aide measures hip flexion PROM and obtains 85° on one trial and 86° on a second trial for the same patient. This small difference most likely reflects:
Anatomy & Kinesiology
6. During a sit-to-stand transfer, the knee moves from approximately 90° of flexion to full extension. This motion takes place primarily in which plane?
Safety & Scope of Practice
7. Which statement BEST describes the role of a PT aide when recording goniometric measurements?
Safety & Scope of Practice
8. A patient's shoulder flexion measures 160° today and was recorded as 145° two weeks ago. Assuming consistent measurement technique, what is the correct action for the PT aide?
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