General Principles of Biomechanics

Question 1

Levers

Answer 1

• rotations of a rigid surface about an axis
• three types

Question 2

First class lever

Answer 2

• occurs when two forces are applied on either side of an axis
  
  • effort is the force that attempts to cause movement
  • resistance is the force that opposes movement
  • ex. in human body is the contraction of triceps at elbow joint

Question 3

Second class lever

Answer 3

• occurs when two forces are applied on one side of an axis
  
  • resistance lies between the effort force and the axis of rotation
  • ex in the body is toe raises

Question 4

Third class lever

Answer 4

• ocurs when two forces are applied on one side of an axis
  
  • the effort force lies closer to the axis than the resistance force
  • most muscles in the human body are third class levels (elbow flexion)

Question 5

Arthrokinematics

Answer 5

• movement between joint surfaces
• three motions
  
  • roll
  • glide
  • spin

Question 6

Roll arthrokinematics

Answer 6

• consists of one joint surface rolling on another
  
  • ex tire rolling on road
  • movement between femoral and tibial articular surfaces

Question 7

Glide arthrokinematics

Answer 7

• consists of a pure translatory motion of one surface gliding on another
  
  • brakes wheel skids

Question 8

Spin arthrokinematics

Answer 8

• consists of a rotation of the moveable component of the joint
  
  • ex movement between joint surfaces of radial head with humerus

Question 9

Osteokinematics

Answer 9

• movement between two bones

Question 10

Convex-concave

Answer 10

• describes relationship between arthrokinematics and osetokinematics

Question 11

Resting/loose packed capsular position

Answer 11

• joint position where capsule and other soft tissues are in most relaxed position
• minimal joint surface contact
• may perform joint play and mobilization techniques in this joint position

Question 12

Close packed position

Answer 12

• joint position where capsule and other soft tissues are maximally tensed
• maximal contaxt between joint surfaces
• joint play and mobilization cannot be properly performed in this position

Question 13

Normal physiological end feel

Answer 13

• soft: occurs with soft tissue approximation
• firm: capsular and ligamentous stretching
• hard: when bone and/or cartilage meet

Question 14

Pathological end feel

Answer 14

• boggy: edema, joint swelling
• firm and decreased elasticity: fibrosis of soft tissue
• rubbery: muscle spasm
• empty: loose, then very hard; associated with muscle guarding or patient avoiding painful part of range
• hypermobility: end feel at a ater time than the opposite side