Lower Limb — MCQs

A 31-year-old female presents with a complaint of Bell's palsy, which had appeared a year earlier and resulted in paralysis of muscles of one side of her face. A nerve graft was performed using a cutaneous nerve from the lower limb to replace the defective facial nerve, and the surgery was successful with restoration of facial muscle function six months post-procedure. The patient reports an area of skin on the lateral aspect of the leg and lateral side of the foot with no sensation. What nerve was likely used in the grafting procedure?

Q198Easy

If the anterior cruciate ligament is torn, how does the tibia move relative to the femur?

Q199Easy

Which passive movement causes weakness in deep posterior compartment syndrome?

Q200Medium

Which of the following ligaments does NOT resist hyperextension of the hip?

Lower Limb Indian Medical PG Practice Questions and MCQs

Question 191: Which of the following nerves is NOT a branch of the lumbar plexus?

A. Obturator nerve
B. Femoral nerve
C. Sciatic nerve (Correct Answer)
D. Lateral cutaneous nerve of thigh

Explanation: **Explanation:** The **Lumbar Plexus** is formed by the ventral rami of spinal nerves **L1 to L4** (with a contribution from T12). It is situated within the posterior part of the Psoas major muscle. **Why Sciatic Nerve is the correct answer:** The **Sciatic nerve (L4–S3)** is the largest nerve in the body and is the primary branch of the **Sacral Plexus**, not the lumbar plexus. It enters the gluteal region via the greater sciatic foramen and supplies the posterior compartment of the thigh and all muscles of the leg and foot. **Analysis of incorrect options:** * **Obturator nerve (L2–L4):** A major branch of the lumbar plexus (anterior divisions). it supplies the medial (adductor) compartment of the thigh. * **Femoral nerve (L2–L4):** The largest branch of the lumbar plexus (posterior divisions). It supplies the anterior compartment of the thigh (extensors of the knee). * **Lateral cutaneous nerve of thigh (L2–L3):** A purely sensory branch of the lumbar plexus that supplies the skin of the lateral thigh. **High-Yield Clinical Pearls for NEET-PG:** 1. **Meralgia Paraesthetica:** Compression of the *Lateral cutaneous nerve of thigh* under the inguinal ligament, causing pain/numbness on the outer thigh. 2. **Lumbosacral Trunk:** Formed by the union of part of the **L4 and L5** rami; it connects the lumbar plexus to the sacral plexus. 3. **Nerve to Psoas Major:** Arises directly from the ventral rami of **L2 and L3**. 4. **Root Value Tip:** Both the Femoral and Obturator nerves share the same root value (**L2, L3, L4**), but the Femoral comes from posterior divisions while the Obturator comes from anterior divisions.

Question 192: Meralgia paresthetica is due to entrapment of which nerve?

A. Medial cutaneous nerve of arm
B. Lateral cutaneous nerve of thigh (Correct Answer)
C. Ilioinguinal nerve
D. Tibial nerve

Explanation: **Explanation:** **Meralgia paresthetica** is a clinical syndrome characterized by tingling, numbness, and burning pain in the outer part of the thigh. It is caused by the compression or entrapment of the **Lateral Cutaneous Nerve of Thigh (LCNT)**, a branch of the lumbar plexus (L2, L3). The LCNT typically enters the thigh by passing deep to or through the **Inguinal Ligament**, just medial to the Anterior Superior Iliac Spine (ASIS). This is the most common site of entrapment. Compression often occurs due to external factors like tight clothing (belts/jeans), obesity, pregnancy, or surgical trauma. **Analysis of Options:** * **Option A (Medial cutaneous nerve of arm):** This nerve arises from the medial cord of the brachial plexus (C8, T1) and supplies the skin of the medial arm. It is unrelated to the lower limb. * **Option C (Ilioinguinal nerve):** While it passes through the inguinal canal, it supplies the skin over the root of the penis/scrotum (or labia majora) and the adjacent medial thigh, not the lateral aspect. * **Option D (Tibial nerve):** A branch of the sciatic nerve, its entrapment at the ankle (flexor retinaculum) leads to **Tarsal Tunnel Syndrome**, affecting the sole of the foot. **High-Yield Clinical Pearls for NEET-PG:** * **Nerve Root:** L2, L3. * **Classic Presentation:** Purely sensory symptoms; there is **no motor deficit** because the LCNT carries no motor fibers. * **Risk Factors:** "Tool-belt syndrome," tight "skinny" jeans, and rapid weight gain/obesity. * **Differential Diagnosis:** Must be distinguished from L3 radiculopathy (which would involve motor weakness and reflex changes).

Question 193: Which of the following is a component of the deltoid ligament?

A. Talofibular ligament
B. Tibiotalar ligament (Correct Answer)
C. Talonavicular ligament
D. Calcaneo-navicular ligament

Explanation: The **Deltoid ligament** (Medial ligament of the ankle) is a strong, triangular band of fibers that stabilizes the medial aspect of the ankle joint. It originates from the apex and borders of the **medial malleolus** and fans out to attach to the tarsal bones. ### Why Option B is Correct: The deltoid ligament is composed of four distinct parts, categorized into superficial and deep layers. The **Tibiotalar ligament** (both anterior and posterior fibers) is a core component. * **Superficial Layer:** Tibionavicular, Tibiocalcaneal, and Posterior Superficial Tibiotalar fibers. * **Deep Layer:** Anterior Deep Tibiotalar and **Posterior Deep Tibiotalar** fibers. The deep layer is the strongest and primarily prevents lateral displacement of the talus. ### Why Other Options are Incorrect: * **A. Talofibular ligament:** This is a component of the **Lateral ligament** of the ankle (along with the calcaneofibular ligament). It is the most commonly injured ligament in inversion ankle sprains. * **C. Talonavicular ligament:** This is part of the dorsal ligaments of the foot, connecting the neck of the talus to the navicular bone; it is not part of the deltoid complex. * **D. Calcaneo-navicular ligament:** Also known as the **Spring ligament**, it supports the head of the talus and maintains the medial longitudinal arch. While the deltoid ligament (tibionavicular part) blends with it, they are distinct anatomical structures. ### NEET-PG High-Yield Pearls: * **Strength:** The deltoid ligament is so strong that in eversion injuries, the medial malleolus usually fractures (avulsion) before the ligament tears. * **Stability:** It is the primary stabilizer against **eversion** of the ankle. * **Spring Ligament:** Always remember that the "Spring ligament" (Plantat calcaneonavicular) is the main supporter of the **Medial Longitudinal Arch**. Loss of this support leads to flat foot (Pes Planus).

Question 194: Which nerve supplies the gamellus inferior muscle?

A. Nerve to obturator internus
B. Nerve to obturator externus
C. Nerve to quadratus femoris (Correct Answer)
D. Ventral rami to S1 and S2

Explanation: The **Gemellus inferior** is one of the small lateral rotators of the hip. Its nerve supply is determined by its anatomical proximity and shared embryological origin with the muscle immediately below it. ### **Why Option C is Correct** The **Nerve to quadratus femoris (L4, L5, S1)**, a branch of the sacral plexus, descends deep to the tendon of the obturator internus and the gemelli muscles. As it passes down to reach the quadratus femoris, it provides a motor branch to the **gemellus inferior**. This is a classic "two-for-one" nerve supply pattern seen in the gluteal region. ### **Analysis of Incorrect Options** * **Option A (Nerve to obturator internus):** This nerve supplies the **Gemellus superior** and the Obturator internus. A common mnemonic is "Superior nerve for superior muscle." * **Option B (Nerve to obturator externus):** This is a branch of the **posterior division of the obturator nerve** (L3, L4). It supplies the obturator externus, which is located in the medial compartment of the thigh, not the gluteal region. * **Option D (Ventral rami S1, S2):** While these segments contribute to the sacral plexus, they do not directly supply the gemellus inferior. The specific segmental origin for the nerve to quadratus femoris is **L4, L5, S1**. ### **High-Yield NEET-PG Pearls** * **The "Sandwich" Rule:** The Obturator internus tendon is "sandwiched" between the Gemellus superior (above) and Gemellus inferior (below). * **Nerve Supply Mnemonic:** * **S**uperior Gemellus = Nerve to Obturator **I**nternus (**S-I**) * **I**nferior Gemellus = Nerve to **Q**uadratus femoris (**I-Q**) * **Action:** All these muscles (Gemelli, Obturator internus, Quadratus femoris) act as **lateral rotators** of the extended thigh and abductors of the flexed thigh.

Question 195: Which nerve is primarily involved in causing foot drop?

A. Deep peroneal nerve
B. Common peroneal nerve (Correct Answer)
C. Anterior tibial nerve
D. Posterior tibial nerve

Explanation: **Explanation:** **Foot drop** is characterized by the inability to dorsiflex the foot at the ankle joint, leading to a characteristic "high-steppage gait." 1. **Why Common Peroneal Nerve (CPN) is correct:** The CPN (L4-S2) is the most frequently injured nerve in the lower limb due to its superficial course as it winds around the **neck of the fibula**. It divides into the superficial and deep peroneal nerves. Injury to the CPN causes paralysis of both the anterior compartment (dorsiflexors) and lateral compartment (evertors) of the leg, as well as sensory loss on the dorsum of the foot. Because it is the parent trunk, its injury is the most common and primary cause of complete foot drop. 2. **Analysis of Incorrect Options:** * **Deep Peroneal Nerve:** While its injury *does* cause foot drop (as it supplies the anterior compartment), it is a branch of the CPN. In clinical exams, if both are listed, CPN is the preferred answer as it is the more common site of entrapment/injury. * **Anterior Tibial Nerve:** This is simply an alternative name for the Deep Peroneal Nerve. * **Posterior Tibial Nerve:** This nerve supplies the posterior compartment (plantarflexors). Injury here would result in an inability to "toe-off" or plantarflex, not foot drop. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Injury:** The neck of the fibula (due to tight casts, leg crossing, or fractures). * **Deformity:** The foot is **"Equinovarus"** (Plantarflexed and Inverted) because the unopposed action of the Tibialis posterior (Tibial nerve) and calf muscles pulls the foot down and in. * **Sensory Loss:** Occurs in the first web space (Deep peroneal) and the majority of the dorsum of the foot (Superficial peroneal).

Question 196: Which of the following statements regarding knee movements is incorrect?

A. Flexion is coupled with lateral rotation of the tibia.
B. There is differential motion between the lateral and medial compartments of the knee.
C. The posterior horns of the menisci move more than the anterior horns during knee movement. (Correct Answer)
D. In full extension, the collateral ligaments of the knee are taut.

Explanation: ### Explanation **1. Why Option C is the Correct (Incorrect Statement):** In the knee joint, the **anterior horns** of the menisci are actually more mobile than the posterior horns. During knee flexion, both menisci move posteriorly, but the total excursion of the **lateral meniscus** is significantly greater (approx. 12mm) than that of the **medial meniscus** (approx. 6mm). This is because the medial meniscus is firmly attached to the deep part of the Medial Collateral Ligament (MCL), making it less mobile and more prone to injury. **2. Analysis of Other Options:** * **Option A:** During the initial stages of flexion (unlocking), the popliteus muscle acts to **medially rotate the femur** on a fixed tibia or **laterally rotate the tibia** on a fixed femur. This is the reverse of the "Screw-home mechanism." * **Option B:** The medial femoral condyle is longer and has a different curvature than the lateral condyle. This results in a "differential motion" where the lateral compartment undergoes more translation while the medial compartment acts more as a pivot. * **Option C:** In **full extension**, the knee is in its most stable (closed-packed) position. Both the Anterior Cruciate Ligament (ACL) and both **collateral ligaments (MCL and LCL) are taut**, providing maximum stability. **3. NEET-PG High-Yield Pearls:** * **Unlocking of the Knee:** Performed by the **Popliteus** muscle (the "Key" to the knee). * **Screw-home Mechanism:** Occurs during terminal extension; involves **medial rotation of the femur** (weight-bearing) or **lateral rotation of the tibia** (non-weight-bearing). * **Meniscal Injury:** The medial meniscus is injured 20 times more frequently than the lateral meniscus due to its relative fixity to the MCL. * **O’Donoghue’s Unhappy Triad:** Injury involving the ACL, MCL, and Medial Meniscus (though recent studies suggest the Lateral Meniscus is often involved in acute tears).

Question 197: A 31-year-old female presents with a complaint of Bell's palsy, which had appeared a year earlier and resulted in paralysis of muscles of one side of her face. A nerve graft was performed using a cutaneous nerve from the lower limb to replace the defective facial nerve, and the surgery was successful with restoration of facial muscle function six months post-procedure. The patient reports an area of skin on the lateral aspect of the leg and lateral side of the foot with no sensation. What nerve was likely used in the grafting procedure?

A. Superficial fibular (peroneal)
B. Tibial
C. Common fibular (peroneal)
D. Sural (Correct Answer)

Explanation: ### Explanation **1. Why the Sural Nerve is Correct:** The **Sural nerve** is the most commonly used donor nerve for autologous nerve grafting (e.g., for facial nerve reconstruction) because of its long length, consistent anatomy, and purely sensory nature [1]. * **Origin:** It is formed by the union of the medial sural cutaneous nerve (from the Tibial nerve) and the lateral sural cutaneous nerve (from the Common Fibular nerve). * **Distribution:** It provides sensation to the **lower posterolateral aspect of the leg** and the **lateral border of the foot** up to the little toe. * **Clinical Correlation:** Harvesting this nerve results in a predictable sensory deficit in the areas mentioned in the question, but no motor loss, making it an ideal graft source. **2. Analysis of Incorrect Options:** * **A. Superficial Fibular (Peroneal) Nerve:** This nerve supplies the lateral compartment muscles (fibularis longus/brevis) and provides sensation to the distal anterolateral leg and the *dorsum* of the foot (except the first web space). * **B. Tibial Nerve:** This is a major mixed nerve (motor and sensory). Using it would cause paralysis of the posterior compartment of the leg (plantarflexors) and loss of sensation to the sole of the foot. * **C. Common Fibular (Peroneal) Nerve:** This is a major mixed nerve. Damage or harvest would lead to "Foot Drop" due to paralysis of the anterior and lateral compartment muscles. **3. NEET-PG High-Yield Pearls:** * **Nerve Grafting Rule:** Always choose a sensory nerve to replace a motor/mixed nerve to minimize functional morbidity. * **Sural Nerve Landmarks:** It runs posteroinferior to the **lateral malleolus** alongside the **small saphenous vein**. * **Great Saphenous Vein Landmark:** Runs anterior to the **medial malleolus** alongside the **saphenous nerve** (a branch of the femoral nerve). * **Facial Nerve Repair:** The sural nerve is frequently used in "Cross-facial nerve grafting" to restore symmetry in long-standing Bell's palsy or facial paralysis [1].

Question 198: If the anterior cruciate ligament is torn, how does the tibia move relative to the femur?

A. Medially
B. Laterally
C. Anteriorly (Correct Answer)
D. Posteriorly

Explanation: **Explanation:** The **Anterior Cruciate Ligament (ACL)** is one of the primary stabilizers of the knee joint. Its fundamental anatomical function is to prevent **excessive anterior translation** of the tibia relative to the femur and to resist internal rotation. 1. **Why "Anteriorly" is correct:** The ACL originates from the anterior intercondylar area of the tibia and attaches to the medial aspect of the lateral femoral condyle. When this ligament is torn, the primary physical restraint against forward movement is lost. Consequently, the tibia slides **anteriorly** (forward) under the femur, a movement clinically demonstrated by the **Anterior Drawer Test** or the **Lachman Test**. 2. **Why other options are incorrect:** * **Posteriorly:** This movement is prevented by the **Posterior Cruciate Ligament (PCL)**. A posterior shift of the tibia indicates a PCL injury (Posterior Drawer sign). * **Medially/Laterally:** Medial and lateral stability (preventing varus/valgus stress) is primarily maintained by the **Medial Collateral Ligament (MCL)** and **Lateral Collateral Ligament (LCL)**, not the ACL. **High-Yield Clinical Pearls for NEET-PG:** * **Lachman Test:** The most sensitive clinical test for an acute ACL tear (performed at 20-30° flexion). * **Unhappy Triad (O'Donoghue’s):** Simultaneous injury to the **ACL, MCL, and Medial Meniscus** (though recent studies suggest the Lateral Meniscus is more commonly injured in acute ACL tears). * **Segond Fracture:** An avulsion fracture of the lateral tibial condyle; it is pathognomonic for an ACL tear. * **Blood Supply:** The ACL is supplied by the **middle genicular artery**.

Question 199: Which passive movement causes weakness in deep posterior compartment syndrome?

A. Foot abduction
B. Foot inversion (Correct Answer)
C. Plantar flexion of foot
D. Foot adduction

Explanation: **Deep Posterior Compartment Syndrome** occurs when increased pressure within the deep posterior compartment of the leg compromises neurovascular structures and muscles [1]. This compartment contains the **Tibialis posterior**, **Flexor digitorum longus**, **Flexor hallucis longus**, and the posterior tibial artery and nerve. 1. **Why Foot Inversion is the Correct Answer:** In compartment syndrome, **passive stretching** of the muscles within the affected compartment causes exquisite pain—often the earliest and most sensitive clinical sign [1]. The primary muscles of the deep posterior compartment (specifically the Tibialis posterior) are responsible for **foot inversion** and plantar flexion. Therefore, passive movement in the opposite direction—**passive eversion** or stretching during movements that tension these tendons—elicits severe pain and functional weakness. In the context of this specific question, the weakness manifests during the active attempt of the muscle's primary action (inversion) due to ischemic pain and pressure. 2. **Analysis of Incorrect Options:** * **Foot Abduction/Adduction:** These are primarily midtarsal joint movements. While Tibialis posterior contributes to adduction, it is not the primary diagnostic stretch trigger for this compartment. * **Plantar flexion:** This is the *active* action of the posterior compartment. Passive *dorsiflexion* (the opposite) would typically be the maneuver used to elicit pain, rather than passive plantar flexion. **NEET-PG High-Yield Pearls:** * **The 6 P’s of Compartment Syndrome:** Pain (out of proportion), Pallor, Paresthesia, Pulselessness, Paralysis, and Poikilothermia. * **Earliest Sign:** Pain on passive stretching of the involved muscles [1]. * **Nerve Involved:** The **Tibial nerve** runs in this compartment; compression leads to sensory loss on the sole of the foot. * **Treatment:** Urgent **fasciotomy** is the definitive management to prevent muscle necrosis and Volkmann’s ischemic contracture [1].

Question 200: Which of the following ligaments does NOT resist hyperextension of the hip?

A. Ischiofemoral ligament
B. Pubofemoral ligament
C. Iliofemoral ligament
D. Sacroiliac ligament (Correct Answer)

Explanation: **Explanation:** The hip joint is a stable ball-and-socket joint reinforced by three strong extracapsular ligaments: the **iliofemoral, pubofemoral, and ischiofemoral ligaments**. These ligaments are arranged in a "spiral" fashion such that they become **taut during extension** and relax during flexion. **Why the Sacroiliac Ligament is the correct answer:** The **Sacroiliac (SI) ligament** is not a ligament of the hip joint. It connects the sacrum to the ilium, functioning to stabilize the sacroiliac joint and transmit weight from the axial skeleton to the lower limbs. It has no role in the range of motion or stability of the femoroacetabular (hip) joint itself. **Analysis of Incorrect Options:** * **Iliofemoral Ligament (Y-ligament of Bigelow):** The strongest ligament in the body. It prevents hyperextension and helps maintain an erect posture without constant muscular activity. * **Pubofemoral Ligament:** Located anteroinferiorly, it limits hyperextension and excessive abduction. * **Ischiofemoral Ligament:** Located posteriorly, it is the weakest of the three but tightens during extension and internal rotation, resisting hyperextension. **NEET-PG High-Yield Pearls:** * **Iliofemoral Ligament:** Often tested as the "strongest ligament in the body." It is shaped like an inverted 'Y'. * **Screw-home mechanism of the hip:** Extension "screws" the femoral head into the acetabulum by tightening these three ligaments, providing maximum stability. * **Ligamentum Teres:** An intracapsular ligament that carries the **acetabular branch of the obturator artery** (crucial for supplying the head of the femur in children).

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Lower Limb — MCQs

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