MSK 12a: gait and nerve injuries of the lower limb

Question 1

Describe the muscles involved in standing at ease

Answer 1

Arrangement of joints so that only a few muscles of back and lower limb are active, therefore minimum of activity required. Hips and knees extended and in their most stable positions; ankle less stable as line of gravity falls between the two limbs just anterior to the axis of rotation of the ankle

Question 2

How is forward way (starting to fall forwards) counteracted?

Answer 2

Bilateral contraction of the calf muscles producing plantar flexion
Spread of the feet increases lateral stability
When lateral sway occurs it is countered by the hip abductors through the iliotibial tract

Question 3

Outline the gait cycle

Answer 3

One gait cycle consists of one cycle of stance and swing by one limb

• stance phase: 60% of the time. Foot is in contact with the ground. Begins with heel strike and ends with push-off
• swing phase: 40% of the time. Foot off the ground, begins after push-off

Question 4

Describe each stage of the stance phase, including the movement and muscles involved

Answer 4

1. HEEL STRIKE (lower forefoot to ground)
   - hip flexion: iliopsoas
   - knee extension: rectus femoris + other quads
   - ankle dorsiflexion: anterior leg muscles
2. LOADING RESPONSE (foot takes load, flat, standing)
   - knee extension: quadriceps
   - ankle neutralised (invertors and evertors)
   - gluteus minimus, medius and tensor fasciae latae: abduct leg and keep pelvis level to help support
3. HEEL OFF (move onto ball of foot)
   - hip extension: hamstrings
   - ankle plantar flexion to accelerate mass: gastrocnemius and soleus
4. PUSH-OFF (/toe off/pre-swing)
   - toe flexion: flexor digitorum longus
   - great toe last to leave ground: flexor hallucis longus
   - ankle plantar flexion: gastrocnemius and soleus

Question 5

Describe the stages of the swing phase including the movements of the muscles involved

Answer 5

1. INITIAL SWING (lift leg and raise foot)
   - hip flexion: iliopsoas and rectus femoris
   - knee flexion: hamstrings
   - ankle dorsiflexion: anterior leg muscles e.g. tibialis anterior
2. SWING LIMB
   - hip flexion: iliopsoas and rectus femoris
   - knee flexion: hamstrings
   - ankle dorsiflexion: anterior leg muscles

Heel hits ground and whole cycle starts again (starting with stance phase)

Question 6

What provides stability to the knee?

Answer 6

Important when the leg is weight-bearing

Lateral stability: tensor fasciae latae, iliotibial tract and fibular collateral ligament

Question 7

What provides ankle stability when it is weight bearing?

Answer 7

Ankle invertors and invertors

Especially important when ground is uneven

Question 8

How is the hip stabilised?

Answer 8

When the foot is raised, gravity pulls the pelvis down. Pelvis is stabilised by gluteus medius and minimus

Question 9

Hip swing

Answer 9

Lateral (OE, OI, S&I G, piriformis, QF) and medial (glut min, med and TFL) rotators involved in swing of hip. Minimises drop in centre of gravity by effectively lengthening the limb

Question 10

What minimises lateral swag?

Answer 10

Adductor brevis, longus, magnus, and gracilis and pectineus (feet rotate towards midline when walking in straight line to minimise lateral shift in centre of gravity)

Question 11

Standing requires minimal energy. What are the positions of the joints?

Answer 11

Hip extended
Knee locked
Lateral stability: TFL, ITT, FCLs and TA
Forward falling prevented by calves

Question 12

Describe some common gait abnormalities

Answer 12

TRENDELENBERG GAIT: waddling gait due to weakness of hip abductors. May be due to lesion of superior gluteal nerve (gluteus medius and minimus affected) or hip instability (e.g. in congenital dislocation of the hip). See characteristic tilting of the pelvis on standing and walking

HIGH STEPPING GAIT: damage to common peroneal nerve. Foot drop

ANTALGIC: “limp”. Shortened stance phase, gentle heel strike. Due to stiffness or abnormal mobility o a joint, so walk in a manner that reduces pain.

Question 13

Describe the Seddon classification for peripheral nerve injuries

Answer 13

1. Neurapraxia temporary conduction block: due to stretch. Least severe. Axons and nerve sheath intact, no Wallerian degeneration. Conduction is intact in the distal and proximal segments of the nerve but there is no conduction in the injured area; hence there is sensory and motor dysfunction distal to the injury site. Complete recovery in days-weeks
2. Axonotmesis nerve damage and axon loss: due to compression and/or traction. Moderate injury: axons damaged, nerve sheath may be disrupted, Wallerian degeneration (distal to injury within 3-4 days). Loss of continuity of axons and myelin sheath, but the endo peri and epineurium are preserved. Partial to full recovery: axon grows at 1-4 mm/day, so the time to recover depends on the distance from the site of injury to the target organ
3. Neruotmesis severed nerve: due to rupture or avulsion. Severe injury: axon and nerve sheath disruption and Wallerian degeneration (distal to site of injury within 3-4 days). Partial or complete division of the axons, endo peri and epi aneurism. No recovery without surgery, as even in an incomplete division the deposition of scar tissue between the divided fascicles prevents regeneration

Question 14

Describe the common presentations of nerve injuries in the lower limb

Answer 14

Nerve root injury due to prolapsed IV disc
Piriformis syndrome: compression of sciatic nerve by piriformis
Meralgia paraesthetica: entrapment of lateral cutaneous nerve of the thigh
Femoral nerve injury
Tibial nerve injury in popliteal fossa
Injuries to common peroneal nerve or its deep/superficial branches
Injury to saphenous nerve during surgery to the great saphenous vein
Injury to sural nerve during surgery to the lesser saphenous vein