Gait

Question 1

Upright posture

Answer 1

• The vertical line of gravity passes posterior to the hip joint and anterior to both the knees and ankles
• Backwards leaning of the trunk w/ respect to the hip is prevented by the iliofemoral ligament
• Hyperextension at the knee is prevented by the posterior knee joint capsule ligaments (cruciates and collaterals)
• Hyperextension at the ankle is prevented by constant contraction of the soleus (only one that is prevented by a muscle)
• Thus the initiation of walking starts w/ relaxing the soleus muscle to begin the forward sway at the ankle

Question 2

The gait cycle

Answer 2

• The gait cycle is broken into 2 parts based on the position of one leg w/ respect to the ground
• The stance phase (60% of the cycle) is further subdivided but is when the leg of interest is planted on the ground
• The swing phase (40% of the cycle) is also subdivided but is when the leg of interest is mostly moving forward, off the ground, to continue the stride
• The body moves up and down 5cm and displaced 5 cm laterally during each gait cycle

Question 3

Role of abductors of the leg in gait

Answer 3

• The primary abductors of the leg (at the hip) are the tensor fascia latae (TFL), gluteus medius and gluteus minimus (all are innervated by the superior gluteal nerve)
• Normal action is to abduct the leg (off the ground), but this can have a second purpose when that leg is on the ground: abduction of the pelvis at the hip
• During gait when one foot is off the ground and the other is on the ground, the side of the planted foot has the hip abductors contract to prevent the contralateral side of the pelvis (the one not supported by the ground) from tilting downward due to gravity
• The leg abductors isometrically contract to stabilize the other side of the pelvis

Question 4

Superior gluteal nerve lesion

Answer 4

• Paralyzes the glut medius, minimus, and TFL
• The body compensates for the inability to stabilize the other side of the pelvis by throwing the trunk toward the stance side (ipsilateral to lesion)
• Called a trendelenburg gait

Question 5

Role of lateral hip rotators in gait

Answer 5

• All of them attach to the greater trochanter of the femur and then deeply placed in the gluteal region (on the posterior side)
• From superior to inferior: priformis, obterator internus, obterator externus, quadratus femoris (don’t need to know any of their innervation)
• As a foot is moved forward (during the swing phase of gait) the lateral rotators on the advancing side contract to keep the toe pointing forward
• Without these muscles the foot would be pointed medially (pigeon-toed), but the muscles rotate the leg laterally to keep the foot pointing forward

Question 6

Role of extensors at the hip joint in gait

Answer 6

• Muscles that extend at the hip and their innervation: gluteus maximus (inferior gluteal), semitendinosus, semimembranosus, biceps femoris long head (all tibial nerve, they also flex at knee)
• Biceps femoris short head is not a hip extensor (only flexor at knee) and is innervated by common fibular nerve
• Walking would lead to slight flexion of the trunk (at the hip joint) at heel-strike, but the hip extensor prevent this
• Hip extensors contract isometrically to counteract the unwanted forward momentum of the trunk (flexion at the hip joint)
• Lesions to tibial and/or inf. gluteal nerves leads to backward throw of trunk during gait to compensate for the lack of these muscles and prevent flexion at the hip

Question 7

Role of flexors at the knee joint in gait

Answer 7

• These muscles are also the semitendiosus (tibial), semimembranosus (tibial), biceps femoris long head (tibial) and short head (common fibular)
• During gait these hamstrings contract eccentrically to act as breaks and slow the forward movement of the leg near the end of swing phase

Question 8

Role of flexors at the hip joint in gait

Answer 8

• Iliopsoas (don’t need to know innervation) and pectineus (femoral nerve) both flex the trunk at the hip
• These muscles contract concentrically to move the leg forward

Question 9

Role of adductors of the leg in gait

Answer 9

• Muscles in the medial compartment of thigh: pectineus (femoral), adductor brevis, adductor longus, adductor magnus, and gracilis (all are obturator nerve)
• During gait these muscle contract to prevent the moving leg from abducting as it is moved forward (keep the leg straight in alignment)

Question 10

Role of extensors at the knee joint in gait

Answer 10

• Muscles in the anterior compartment: quadriceps femoris, vastus lateralis, vastus medius, vastus intermedius (all femoral nerve)
• During gait they contract to prevent unwanted flexion at the knee when the knee is loaded during the early stance phase (right when the weight is shifted to the planted leg)

Question 11

Role of plantar flexors at the ankle joint in gait

Answer 11

• Muscles in the posterior compartment of the distal leg (gastrocnemius, soleus, tibialis posterior and flexor hallucis longus) are innervated by the tibial nerve
• These muscles contract concentrically during gait to provide forward thrust at the end of the stance phase
• These muscle produce the “heel off” function during the stance cycle
• Loss of the plantar flexors leads to inability to raise the heel off the ground
• This forces the pt to take small steps and drag the limb forward using hip flexors

Question 12

Role of dorsiflexors (foot extensors) at the ankle joint in gait

Answer 12

• Primary dorsiflexors at the ankle (extensor digitorum longus, extensor hallucis longus, and tibialis anterior) are all innervated by the deep fibular nerve
• During gait these muscles contract so the toe clears the ground during swing phase
• They also contract at heel strike to lower the foot in a controlled manner
• Loss of ankle extensors means the foot cannot decelerate at heel strike and the toes cannot clear the ground during swing phase
• This results in a high-stepping gait and foot-slap

Question 13

Putting the muscles involved in gait together

Answer 13

• There are many muscles involved in each part of gait, but we only care about the most important ones for a give phase
• Will be focusing only on the right foot, starting the cycle at one heel strike (R) and finishing w/ the next heel strike (R)

Question 14

Heel strike

Answer 14

-The ankle dorsiflexors (extensors) contract eccentrically to offset gravity and set the foot on the ground in a controlled fashion

Question 15

Foot flat

Answer 15

• THe gluteus medius and minimus contract isometrically to prevent the pelvis from tilting to side of the limb that is in swing phase
• The R glut med and min contract so the left side of the pelvis doesn’t sag downward b/c it is no longer supported by gravity (L limb is in swing phase)

Question 16

Mid-stance

Answer 16

• Gluteus medius and minimus are still contracting isometrically to keep pelvis from tilting to the opposite side (side w/ limb in swing phase)
• Same as mid-stance

Question 17

Heel off

Answer 17

• Gluteus medius and minimus are still contracting isometrically to keep pelvis from tilting to the opposite side (side w/ limb in swing phase)
• But not the plantar flexors are also contracting concentrically to lift heel off the ground

Question 18

Toe off

Answer 18

• Plantarflexors continue to contract concentrically to provide forward thrust
• The hip flexors contract concentrically to stop extension at the hip and initiate forward movement of the limb

Question 19

Early swing

Answer 19

• Hip flexors contract concentrically to accelerate forward motion of the limb
• Ankle dorsiflexors (extensors) contract concentrically to lift toes and prevent them from stubbing the ground

Question 20

Late swing

Answer 20

-Dorsiflexors at the ankle (foot extensors) switch to isometric contraction to hold the toes up in readiness for heel strike

Question 21

Gait abnormalities 1

Answer 21

• Lesioning the superior gluteal nerve: leads to excessive pelvic tilt on the contralateral side (trendelenburg gait) due to paralysis of glut med and min
• Lesions to nerve innervating iliopsoas: walking virtually impossible b/c cannot bring leg forward
• Lesion to tibial nerve in the thigh paralyzes the hamstring and forces pt to lean backwards at the moment of heel-strike to prevent jack-knifing of the trunk

Question 22

Gait abnormalities 2

Answer 22

• Lesions to the femoral nerve paralyzes the quads, thus the pts need to extend the knee thru another way (besides using the quads). They do this by using the momentum of the leg to carry the knee into extension just before heel-strike, then lean forward on the knee to keep it extended
• Lesions of the tibial nerve in the popliteal fossa results in paralysis of the calf muscles. Pts w/ this lesion will lean backward and take short steps. They also can’t plantar flex so the foot and leg stay on the ground. Results in a shuffling gate b/c they rely on hip flexors to move foot forward on the ground

Question 23

Gait abnormalities 3

Answer 23

• Paralysis of the dorsiflexors (foot extensors) from a lesion to the deep or common fibular nerve (very common) leads to high-stepping gait (increases flexion at the knee so toes clear ground) and foot slapping (placing the entire foot on the ground all at once)
• Paralysis of the adductor muscles due to lesion of the obturator nerve results in the lower limb of the ipsilateral side being slightly abducted during the swing phase (swings out laterally)