Somatic Lower Extremity

General rule for posterior thigh muscle innervation

Sciatic nerve (Tibial division).

General rule for posterior thigh muscle actions

Hip extension and knee flexion.

Exception to posterior thigh muscle general rules

Biceps femoris short head (origin: linea aspera, innervation: common fibular division).

Semitendinosus insertion

Pes anserinus (proximal, anterior, medial tibial shaft).

Biceps femoris long head vs. short head origin

Long head: Ischial tuberosity. Short head: Distal 1/2 of linea aspera.

Quadriceps common insertion

Tibial tuberosity via patellar tendon, patella, and patellar ligament.

General innervation of anterior thigh muscles

Femoral nerve.

Rectus femoris origins

Anterior inferior iliac spine (AIIS) and superior acetabulum.

Sartorius actions

Hip flexion, abduction, lateral rotation, and knee flexion (figure-4 position).

Iliopsoas insertion

Lesser trochanter of femur.

Pectineus double innervation

Femoral nerve (2/3) and Obturator nerve (1/3).

Function of Articularis Genu

Pulls suprapatellar bursa and synovial membrane upward during knee extension.

General rules for medial thigh compartment

Origin on pubis, insertion on femur, action hip adduction, innervation obturator nerve.

Adductor magnus dual innervation

Adductor part: Obturator nerve. Hamstring part: Sciatic nerve (Tibial division).

Muscles attaching to the pes anserinus

Sartorius, Gracilis, and Semitendinosus.

General innervation of posterior leg compartment

Tibial nerve.

Popliteus function at the knee

Unlocks the extended knee via medial rotation of tibia (or lateral rotation of femur).

Muscles forming the Triceps Surae

Gastrocnemius (medial and lateral heads) and Soleus.

Mnemonic 'Tom, Dick, AN' Harry' for tarsal tunnel (ant to post)

Tibialis posterior, Flexor Digitorum longus, Artery (post. tibial), Nerve (tibial), Flexor Hallucis longus.

General rules for anterior leg compartment

Action dorsiflexion/digit extension, innervation deep fibular nerve.

Tibialis anterior insertions

Inferior base of 1st metatarsal and medial/inferior aspect of medial cuneiform.

General rules for lateral leg compartment

Action ankle eversion and plantar flexion, innervation superficial fibular nerve.

Muscles forming the anatomical stirrup of the foot

Tibialis anterior and Fibularis longus.

Foot intrinsic muscles innervated by Medial Plantar Nerve

Abductor hallucis, Flexor digitorum brevis, Flexor hallucis brevis, Lumbrical 1.

Gluteus maximus insertion

Upper fibers: IT band (Gerdy's tubercle). Lower fibers: Gluteal tuberosity.

Clinical sign of Gluteus Medius/Minimus weakness

Trendelenburg sign (unsupported pelvis drops during single-leg stance).

Gluteus medius & minimus primary innervation

Superior gluteal nerve.

Tensor Fascia Lata insertion

Gerdy's tubercle of tibia via IT band.

Deep lateral rotators of the hip (6 muscles)

Piriformis, Superior gemellus, Obturator internus, Inferior gemellus, Quadratus femoris, Obturator externus.

Most common relationship of Sciatic Nerve to Piriformis (Type A)

Entire sciatic nerve passes inferior/underneath the piriformis muscle (80-90%).

Lumbar plexus spinal segments and location

Formed by L1-L4 spinal nerves within the psoas major muscle.

Sacral plexus spinal segments and location

Formed by L4-S4 spinal nerves on the anterior surface of the piriformis muscle.

Saphenous nerve origin and cutaneous distribution

Terminal branch of femoral nerve supplying skin of the medial knee, leg, and foot.

Meralgia paresthetica cause and nerve involved

Compression of the lateral femoral cutaneous nerve causing pain and paresthesia in lateral thigh.

Key dermatomes for L3 and L4

L3 innervates anterior thigh and medial knee; L4 innervates medial leg and foot.

Key dermatomes for L5 and S1

L5 innervates anterior leg and dorsum of foot; S1 innervates lateral leg and foot.

Deep fibular nerve cutaneous innervation

Skin on the dorsum of the foot between the 1st and 2nd toes.

Femoral triangle contents (lateral to medial)

Femoral Nerve, Femoral Artery, Femoral Vein, Lymphatics (NAVL).

Femoral triangle borders

Superior: Inguinal ligament. Lateral: Medial border of sartorius. Medial: Medial border of adductor longus.

Femoral artery continuation

Passes through adductor hiatus to continue as the popliteal artery.

Branches of the deep femoral artery

Medial femoral circumflex, lateral femoral circumflex, and perforating branches.

Arteries of the cruciate anastomosis

Medial femoral circumflex, lateral femoral circumflex, 1st perforating branch of deep femoral, and inferior gluteal.

Anterior tibial artery termination

Passes under extensor retinaculum to terminate as the dorsalis pedis artery.

Great saphenous vein drainage

Drains medial foot, leg, and thigh into the femoral vein.

Small saphenous vein drainage

Drains lateral foot and leg into the popliteal vein.