Innervation of the Lower Limb Flashcards
What are the 3 types of joints within the body?
- ball and socket joint e.g. hip joint
- hinge joint e.g. elbow
- ellipsoidal/condyloid joint e.g. carpal (not as flexible as ball and socket)
What are the major functions of the lower limb?
- weight-bearing
- maintaining body posture
- locomotion
Where is the sacroiliac joint?
between the pelvis and the sacrum
What are the 6 regions of the lower limb?
- hip
- thigh
- knee
- leg
- ankle
- foot
Where are the ‘knuckles’ of the feet?
in between the phalanges and the metatarsals
What does the calcaneus develop in very heavy individuals?
osteophytes (calcaneal spurs)
What are the bones and movements of the hip joint?
- pelvis and femur
- flexion, extension, abduction, adduction, circumduction, medial and lateral rotation
What are the bones and movements of the knee joint?
- femur and tibia
- flexion, extension and rotation
What are the bones and movements of the ankle joint?
- tibia, fibula and talus
- dorsiflexion and plantarfelxion
What are the bones and movements of the sub-talar joint?
- talus and calcaneus
- inversion and eversion of the foot
What are the bones and movements of the MTP joint?
- metatarsal and phalanges
- flexion, extension, abduction, adduction and circumduction
What are the bones and movements of the PIP and DIP (interphalangeal) joint?
- phalanges
- flexion and extension
What are the 3 nerves that arise from the lumbosacral plexus?
- femoral nerve
- obturator nerve
- sciatic nerve
Which 2 nerves arise from the sciatic nerve?
- tibial nerve
- common peroneal (fibular) nerve
What is the greater sciatic foramen?
an opening in the posterior pelvis formed by the sacrotuberous and sacrospinous ligaments that sit below the piriformis muscle
What does the femoral nerve arise from?
the lumbar plexus (L2-L4) within the substance of the psoas major
Describe the pathway of the femoral nerve
it passes between the iliacus and psoas major muscles in the abdomen then enters the thigh by passing behind the inguinal ligament to supply muscles of the anterior compartment of the thigh (quadriceps femoris)
What are the 4 muscles of the quadriceps femoris?
- rectus femoris
- vastus lateralis
- vastus intermedius
- vastus medialis
What are the main functions of the quadriceps femoris?
to flex the hip and extend the knee joint
What are the 2 sensory branches formed by the femoral nerve as it travels down the limb?
- saphenous nerve supplies the medial skin of the leg
- anterior femoral cutaneous nerve supplies the skin on the front of the thigh and knee as well as the medial aspect of the thigh
What is the knee-jerk reflex?
simple reflex that causes the contraction of the quadriceps muscle when the patellar tendon is stretched and is used to test L2-L4
How may injury to the femoral nerve occur?
- haematomas in the iliacus muscle
- pelvic/inguinal hernia/hip surgery
- pelvic fracture
What does injury to the femoral nerve result in?
- loss of extension at the knee joint (from paralysis of the quadriceps femoris muscle)
- impaired hip flexion
- sensory loss over the anterior thigh and knee
- sensory loss over the medial thigh, knee, leg and foot
- loss of the knee jerk reflex
Describe the pathway of the obturator nerve
descends in the psoas major muscle, then along the lateral pelvic wall then passes through the obturator foramen and enters the medial compartment of the thigh
What does the obturator nerve supply?
- muscles in the medial compartment of the thigh
- skin on the inferomedial aspect of the thigh
What is the main function of the muscles in the medial compartment of the thigh?
adduction of the thigh at the hip joint
What are the 4 adductor muscles of the thigh?
- adductor Magnus
- adductor longus
- adductor brevis
- gracilis
What can happen due to a pelvic fracture?
the bony fragments severing the obturator nerve
What does injury to the obturator nerve result in?
weakness of thigh adduction and sensory loss over skin of the inferomedial thigh
What is the obturator foramen?
a large opening in the pelvic bone that the obturator nerve travels through
When is there a high risk of obturator hernias?
during pregnancy due to relaxation of the pelvic peritoneum and a wider and more horizontal obturator canal
What does the sciatic nerve arise from?
the lumbosacral plexus (L4-S3)
What is the largest nerve in the body?
the sciatic nerve
Describe the pathway of the sciatic nerve
- it leaves the pelvis via the greater sciatic foramen and enters the gluteal region (buttock)
- it then descends into the posterior compartment of the thigh, where it lies behind the adductor magnus and is crossed posteriorly by the long head of biceps femoris
What is the biceps femoris?
long muscle in the lateral side of the posterior compartment of the thigh (hamstring) responsible for hip extension and knee flexion
What are the hamstring muscles at the medial side?
semitendinosus and semimembranosus muscles
What does the sciatic nerve supply?
all of the hamstring muscles
Where does the sciatic nerve divide and into what?
near the apex of the popliteal fossa (back of the knee) into the tibial nerve and the common peroneal nerve
What supplies the sensory function to the back of the thigh?
posterior cutaneous nerve
What does the posterior cutaneous nerve originate from?
the Sacral plexus (S1-S3)
What can cause injury to the sciatic nerve?
injections into gluteus maximus, hip trauma, hip surgery and prolonged pressure due to immobility
What does injury to the sciatic nerve result in?
- loss of knee flexion and impaired hip extension
- loss of dorsiflexion, plantarflexion, inversion and eversion of the foot
- sensory loss over lateral leg and over whole foot except medial aspect
Describe the pathway of the tibial nerve
it descends through the popliteal fossa then passes into the back of the leg then enters the foot where it divides into the medial and lateral plantar nerves
What does the tibial nerve supply?
all superficial and deep muscles of the posterior leg and foot
What is the popliteal fossa?
a diamond-shaped depression located posterior to the knee joint
Where is the FDL and what is it responsible for?
all the way down to the toes responsible for flexing the digits
Where does the FHL go?
the big toe
What is the sural nerve?
a sensory branch that originates form the tibial nerve and goes to the skin of the posterior leg
What do the medial and lateral plantar nerves supply?
muscles and skin on the sole of the foot
What can cause injury to the tibial nerve?
compression by a Baker’s cyst posterior to the knee, or (distally) due to foot and ankle trauma
What does injury to the tibial nerve result in?
- loss of plantarflexion of the foot and flexion of the toes
- sensory loss over posterolateral leg, sole and lateral aspect of foot
What does the common peroneal nerve arise as?
the smaller terminal portion of the sciatic nerve in the popliteal fossa (L4-S2)
Describe the pathway of the common peroneal nerve
- it descends laterally along the medial border of the biceps femoris muscle and winds around the neck of the fibula
- it then enters the lateral compartment of the leg and divides into the superficial and deep peroneal nerves
What does the superficial peroneal nerve supply?
the muscles of the lateral compartment of the leg whose function is to evert the foot
What muscles does the deep peroneal nerve supply?
the muscles in the anterior compartment of the leg
What are the functions of the muscles of the anterior compartment of the leg?
to dorsiflex the foot, invert the foot and extend the toes
What can cause injury to the common peroneal nerve?
a fracture of the neck of the fibula or compression at this site
What does injury to the common peroneal nerve result in?
- “foot drop” (loss of dorsiflexion and eversion of the foot)
- loss of sensation on the anterolateral aspect of the leg and dorsum of the foot
What are the functions and nerves of the muscles in the 3 thigh compartments?
- anterior = knee extension by femoral nerve
- medial = hip adduction by obturator nerve
- posterior = knee flexion by sciatic nerve
What are the functions and nerves of the muscles in the 3 leg compartments?
- anterior = foot dorsiflexion at ankle joint by deep peroneal nerve
- lateral = foot eversion at subtalar joint by superficial peroneal nerve
- posterior = inversion at subtalar joint and foot plantar flexion at ankle joint by tibial nerve