Gait Cycle Kinetic Motions (O'Sullivan)

Question 1

HIP KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

heel strike

Answer 1

EXT FORCES: reaction force in front of joint; flexion moment moving toward extension; forward pelvic rotation

INT FORCES: gluteus maximus and hamstrings work eccentrically to resist flexion moment; erector spine working eccentrically to resist forward bend

Question 2

KNEE AND TIBIA KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

heel strike

Answer 2

EXT FORCES: rapidly increasing reaction forces behind knee joint cause flexion moment

INT FORCES: quadriceps femoris contracting eccentrically to control rapid knee flexion and prevent buckling

Question 3

FOOT AND ANKLE KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

heel strike

Answer 3

EXT FORCES: reaction forces behind joint axis: PF moment at heel strike

INT FORCES: DF (tibialis ant, ext digitorum longus and ext hallucis longus) contract eccentrically to slow PF

Question 4

HIP KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

foot flat

Answer 4

EXT FORCES: flexion moment

INT FORCES: gluteus maximus and hamstrings contracting concentrically to bring hip into extension

Question 5

KNEE AND TIBIA KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

foot flat

Answer 5

EXT FORCES: flexion moment

INT FORCES: after foot is flat, quadriceps femoris activity, becoming concentric to bring femur over tibia

Question 6

FOOT AND ANKLE KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

foot flat

Answer 6

EXT FORCES: maximum PF moment; reaction forces beginning to shift anterior, producing a DF moment

INT FORCES: PF muscles (gastroc-soleus and peroneal muscles) activated to control DF of tibia and fibula over fixed foot, contracting eccentrically

Question 7

HIP KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

midstance

Answer 7

EXT FORCES: reaction force posterior to hip joint; extension moment

INT FORCES: iliopsoas activity continuing

Question 8

KNEE AND TIBIA KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

midstance

Answer 8

EXT FORCES: reaction forces moving anterior to joint extension moment

INT FORCES: gastrocnemius beginning to work concentrically to start knee flexion

Question 9

FOOT AND ANKLE KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

midstance

Answer 9

EXT FORCES: slight DF moment

INT FORCES: P muscles (gastoc-soleus and peroneal mm) activated to control DF of tibia and fibula over fixe foot, contracting eccentrically

Question 10

FOOT AND ANKLE KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

heel off

Answer 10

EXT FORCES: max DF moment

INT FORCES: PF muscles beginning to contract concentrically to prepare for push-off

Question 11

HIP KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

toe off

Answer 11

EXT FORCES: decrease of extension moment

INT FORCES: adductor magnus working eccentrically to control or stabilize pelvis; iliopsoas activity continuing

Question 12

KNEE AND TIBIA KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

toe off

Answer 12

EXT FORCES: reaction forces moving posterior to joint as knee flexes; flexion moment

INT FORCES: quadriceps femoris contracting eccentrically

Question 13

FOOT AND ANKLE KINETIC MOTION
(EXTERNAL AND INTERNAL FORCES)

toe off

Answer 13

EXT FORCES: DF moment

INT FORCES: PF muscles at peak activity but becoming inactive as foot leaves ground

Question 14

KINETIC MOTION

acceleration to midswing

Answer 14

HIP: hip flexors working concentrically to bring limb through; contralateral gluteus medium contracting to maintain pelvis position

KNEE: hamstrings concentrically contracting

ANKLE/FOOT: DF contracting concentrically

Question 15

KINETIC MOTION

midswing to deceleration

Answer 15

HIP: gluteus maximus contracting eccentrically to slow hip flexion

KNEE: quadriceps femoris contracting concentrically and hamstrings contracting eccentrically

ANKLE/FOOT: DF contracting isometrically