Angular Kinematics

Angular Motions

all parts of the body move through the same angle but do not undergo the same linear displacement

Where does angular motion occur

about an axis of rotation

Relative Joint Angle

the angle between two longitudinal axes of two segments

Examples of relative joint angles

between shoulder and elbow and elbow and hand

3 Points of Interest Needed for Relative Joint Angles

proximal, vertex and distal points

Calculating Relative Joint Angles

use cosine law - C2 = A2 + B2 - 2AB cos c

Also need length of each segment - A2 + B2 = C2

Absolute Angles

the angle of inclination of a body segment relative to some fixed reference in the environment

2 Points of Interest Needed for Absolute Angles

proximal and distal points

Calculating Absolute Angles

Angles calculated using the tangent (ratio b/w opposite and adjacent angles)

Tan 0 =Yprox - Ydistal / Xprox - X distal

Anatomical Anlges

measured relative angle is compared to angle of joint in the anatomical position

Hip Angular Motion - Marker Locations

torso, hip, knee

Hip Angular Motion - Formula

180 - relative angle of hip

Hip Angular Motion

60% is stance, 40% is swing

extension - close to toe off (> 180 degrees)

Knee Angular Motion - Marker Locations

hip, knee, ankle

Knee Angular Motion - Formula

180 - relative angle of knee

Knee Angular Motion

no negative values - don’t hyperextend knee

Ankle Angular Motion - Marker Locations

knee, ankle, toe

Ankle Angular Motion - Formula

90 - relative angle of ankle

Ankle Angular Motion

positive = dorsiflexion, < 90 degrees

negative = plantar flexion, > 90 degrees

Rearfoot Angle

0 leg = 0 calcaneous

Rearfoot Angle - At Neutral Position

90° - 90° =0°

Rearfoot Angle - Supination

positive angle

example: 90-82 =8°

Rearfoot Anlge - Pronation

negative angle

example: 90-95=-5°