Lower limb muscles (for nerds 🤓)

Lower extremity nerves

Innervation of the lower extremity (ventral view)

• More details on nerves (not important)

Innervation of the lower extremity (dorsal view)

• More details on nerves (not important)

• Motor: Transversus abdominis and internal oblique | - Herniorrhaphy
• Laparoscopic surgery | - Pain in anterior scrotum/labia majora , base of penis/mons pubis , medial thigh | | Iliohypogastric (T12-L1) | - Sensory: Suprapubic region
• Motor: Transversus abdominis and internal oblique | - Abdominal surgery (appendectomy, inguinal hernia repair) | - Burning or tingling pain in surgical incision site radiating to inguinal and suprapubic region | | Genitofemoral nerve (L1-L2) | - Sensory: Scrotum/labia majora, medial thigh
• Motor: Cremaster | - Laparoscopic surgery | - ↓ sensation in upper medial thigh and anterior thigh beneath the inguinal ligament (lateral part of the femoral triangle)
• Absent cremasteric reflex | | Lateral femoral cutaneous (L2-L3) | - Sensory: anterior and lateral thigh | - Tight clothing
• Obesity
• Pregnancy
• Pelvic procedures | - ↓ thigh sensation (anterior and lateral)

Meralgia paresthetica

• Compression of the lateral femoral cutaneous nerve by inguinal ligament - Tingling, numbness, burning pain in anterolateral thigh | | Obturator (L2-L4) | - Sensory: medial thigh
• Motor: obturator externus, adductor longus, adductor brevis, gracilis, pectineus, adductor magnus | - Pelvic surgery | - ↓ thigh sensation (medial) and adduction | | Femoral (L2-L4) | - Sensory: anterior thigh, medial leg
• Motor: quadriceps, iliacus, pectineus, sartorius | - Pelvic fracture
• Compression from **retroperitoneal hematoma (**in an anticoagulated patient) ****or psoas abscess 🖼
• During childbirth 🖼 | - ↓ leg extension
• ↓ patellar reflex | | Sciatic 🖼 (L4-S3) | - Motor: semitendinosus, semimembranosus, biceps femoris, adductor magnus
• Sensory: posterior thigh, posterior knee, and all below knee (except narrow band on medial lower leg) | - Herniated disc - Posterior hip dislocation
• piriformis syndrome
• Hip fracture/arthroplasty

→ Sciatic nerve passes between piriformis & superior gemellus. | - Splits into common peroneal and tibial nerves | | Common (fibular) peroneal (L4-S2) | Superficial peroneal nerve

• Sensory: dorsum of foot (except webspace between hallux and 2nd digit)
• Motor: peroneus longus and brevis → eversion

**Deep peroneal nerve

• Sensory**: webspace between hallux and 2nd digit
• Motor: tibialis anterior→ dorsiflexion | - Trauma or compression of lateral aspect of leg - Fibular neck fracture
• Extrinsic compression (eg, pressure from cast, surgical positioning) at the fibular head. | **PED = Peroneal Everts and Dorsiflexes

-** Loss of sensation on dorsum and medial foot

• Foot drop: foot is inverted and plantarflexed at rest
• steppage gait | | Tibial (L4-S3) | - Sensory: sole of foot
• Motor: biceps femoris (long head), triceps surae, plantaris, popliteus, flexor muscles of foot | Proximal lesion - Knee trauma
• Baker cyst

Distal lesion

• Tarsal tunnel syndrome | **TIP = Tibial Inverts and Plantarflexes

-** Inability to curl toes and loss of sensation on sole and lateral foot. In proximal lesions

• Foot everted at rest with weakened inversion and plantar flexion | | Superior gluteal (L4-S1) | - Motor: gluteus medius, gluteus minimus, tensor fascia latae | - Iatrogenic injury during intramuscular injection to superomedial gluteal region

• Prevent by choosing superolateral quadrant, preferably anterolateral region. | Trendelenburg sign/gait

• Pelvis tilts because weight-bearing leg cannot maintain alignment of pelvis through hip abduction

• Lesion is contralateral to the side of the hip that drops, ipsilateral to extremity on which the patient stands | | Inferior gluteal (L5-S2) | - Motor: gluteus maximus | - Posterior hip dislocation | - Difficulty climbing stairs, rising from seated position

• Loss of hip extension | | Pudendal (S2-S4) | - Sensory: perineum - Motor: external urethral and anal sphincters | - Stretch injury during childbirth

• Prolonged cycling

• Horseback riding | - Loss of sensation in perineum and genital area

• Fecal and/or urinary incontinence, ↓ anal wink

• Can be blocked with local anesthetic during childbirth using ischial spine as a landmark for injection |

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Clues to diagnose: Patient undergone laparoscopic surgery and suffered from postoperative ↓ in the upper medial thigh sensation

• Intact cremasteric reflex → Ilioinguinal nerve injury
• Absent cremasteric reflex → Genitofemoral nerve injury </aside>

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Piriformis syndrome

• Definition
  • Sciatica-like symptoms which originate due to compression of sciatic nerve by piriformis injury or hypertrophy.
• Anatomy
  • The piriformis muscle arises from the sacrum, passes through the greater sciatic foramen (occupying most of its space), and inserts on the greater trochanter.
    • Structures passing above the piriformis→ Superior gluteal vessels and superior gluteal nerve.
    • Structures passing below the piriformis → Inferior gluteal vessels and nerve, internal pudendal vessels and pudendal nerve, and sciatic nerve.
      • Explanatory picture </aside>

The femoral nerve descends through the psoas major muscle, emerges laterally between the psoas and iliacus muscle, and then runs beneath the inguinal ligament.

Hip Region

Hip muscles

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The rectus femoris, iliopsoas, and sartorius are the major hip flexors.

• Rectus femoris and sartorius also affect knee movement.
  • The sartorius flexes the knee
  • The rectus femoris extends the knee. </aside>

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Muscles used when sitting up from the supine position

• The external abdominal obliques
• The rectus abdominis
• The hip flexors (most importantly iliopsoas). </aside>

Important to recognize the sites of gluteal muscles on CT A) rectus muscle→ play an important role in Valsalva maneuver B) Illiacus ms C) Gluteus minimus ms D) Gluteus Medius ms E) Gluteus maximus ms

          **Psoas muscle is present beside the vertebral body**

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Anatomical relations

• Gluteus Medius, minimus → insert into greater trochanter.
• Iliopsoas → insert into lesser trochanter. </aside>

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Hamstring muscles

• Origin → Ischium
• Action→ Flexion of the knee , Extension of the hip
• Cause of injury→ Sudden deceleration during running (when muscles contract to slow the lower extremity)
  • Muscles of hamstrings </aside>

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Which hip movement will be most affected following this fracture ?

• Answer </aside>

Hip dislocation

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Femoral neck fracture

• Posterior hip dislocation can be mistaken for femoral neck fracture, which can also present with leg shortening; however, the leg is typically rotated externally and abducted due to action of iliopsoas.

  • Explanatory picture

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  Clues to diagnose

  • Shortened hip
  • Lengthened hip + external rotation + abduction → Anterior hip dislocation </aside>

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Avascular Necrosis of Bone