Lower Limb — MCQs

Lower Limb Indian Medical PG Practice Questions and MCQs

Question 301: A serious complication of fractures of the femoral neck is avascular necrosis of the femoral head. This usually results from rupture of which artery?

A. Acetabular branch of obturator
B. Deep circumflex iliac
C. Descending branch of lateral circumflex femoral
D. Medial circumflex femoral (Correct Answer)

Explanation: The blood supply to the head of the femur is derived from three main sources: the trochanteric anastomosis (retinacular arteries), the cruciate anastomosis, and the artery of the ligamentum teres. The **Medial Circumflex Femoral Artery (MCFA)** is the most significant contributor. It gives off **superior and inferior retinacular branches** that pierce the joint capsule and run along the femoral neck to reach the head. In intracapsular fractures of the femoral neck, these retinacular vessels are frequently torn or compressed, leading to ischemia and subsequent **Avascular Necrosis (AVN)**. **Analysis of Options:** * **Option A (Acetabular branch of obturator):** This artery travels within the ligamentum teres. While it supplies the head in children, it becomes insufficient to maintain viability in adults. * **Option B (Deep circumflex iliac):** This is a branch of the external iliac artery supplying the iliac crest and abdominal wall; it does not contribute to the femoral head. * **Option C (Descending branch of lateral circumflex femoral):** This branch travels inferiorly to participate in the genicular anastomosis around the knee. While the *lateral* circumflex femoral artery does contribute to the trochanteric anastomosis, the *medial* artery is the dominant source for the head. **Clinical Pearls for NEET-PG:** * **Intracapsular vs. Extracapsular:** AVN is a risk in *intracapsular* fractures (neck) but rarely in *extracapsular* fractures (intertrochanteric) because the latter occur distal to the retinacular vessel insertion. * **Garden Classification:** Used to predict the risk of AVN based on the degree of displacement in femoral neck fractures. * **Cruciate Anastomosis:** Formed by the Medial circumflex femoral, Lateral circumflex femoral (transverse branch), First perforating, and Inferior gluteal arteries.

Question 302: The talus bone articulates with all of the following EXCEPT:

A. Calcaneum
B. Tibia
C. Navicular
D. Cuboid (Correct Answer)

Explanation: The **talus** is a unique bone in the foot as it has no muscular or tendinous attachments and is covered largely by articular cartilage. It serves as the primary link between the leg and the foot. ### **Why Cuboid is the Correct Answer** The talus does **not** articulate with the cuboid. The cuboid bone is located on the lateral side of the midfoot and articulates posteriorly with the **calcaneus** (at the calcaneocuboid joint) and anteriorly with the 4th and 5th metatarsals. There is no direct contact between the talus and the cuboid. ### **Analysis of Incorrect Options** * **Tibia (Option B):** The superior surface (trochlea) of the talus articulates with the distal end of the tibia to form the **ankle joint** (talocrural joint). This is a hinge joint responsible for dorsiflexion and plantarflexion. * **Calcaneum (Option A):** The talus articulates with the calcaneus inferiorly at two points: the **subtalar joint** (posteriorly) and the **talocalcaneonavicular joint** (anteriorly/medially). These joints allow for inversion and eversion. * **Navicular (Option C):** The rounded head of the talus articulates anteriorly with the posterior surface of the navicular bone. ### **High-Yield Clinical Pearls for NEET-PG** * **Blood Supply:** The talus has a retrograde blood supply, primarily via the **Artery of the Tarsal Canal** (branch of the posterior tibial artery). Fractures of the neck of the talus carry a high risk of **Avascular Necrosis (AVN)**. * **Attachments:** It is the only bone in the foot with **no muscle attachments**. * **Joint Type:** The ankle joint is a synovial joint of the **hinge** variety. Synovial fluid provides nutrition for the articular hyaline cartilage, which lacks a direct blood supply [1]. * **Keystone:** The talus acts as the "keystone" of the **medial longitudinal arch** of the foot.

Question 303: The blood supply to the femoral head is mostly by which artery?

A. Lateral circumflex femoral artery
B. Medial circumflex femoral artery (Correct Answer)
C. Artery of ligamentum teres
D. Obturator artery

Explanation: The blood supply to the femoral head is a high-yield topic in NEET-PG, as it explains the risk of avascular necrosis (AVN) following femoral neck fractures. ### **Explanation** The **Medial Circumflex Femoral Artery (MCFA)** is the primary source of blood to the femoral head. It gives off **retinacular arteries** (mainly the posterosuperior and posteroinferior groups) that pierce the joint capsule and run along the neck to reach the head. These vessels provide the vast majority of the blood supply required for the viability of the femoral head in adults. ### **Why other options are incorrect:** * **Lateral Circumflex Femoral Artery (LCFA):** While it contributes to the extracapsular arterial anastomosis around the hip, its branches (mainly the ascending branch) provide significantly less blood to the head compared to the MCFA. * **Artery of Ligamentum Teres:** This is a branch of the **Obturator artery**. In adults, it is often rudimentary and supplies only a small area around the fovea capitis. It is insufficient to maintain the viability of the head if the retinacular vessels are damaged. * **Obturator Artery:** It gives rise to the artery of the ligamentum teres but does not provide direct significant perfusion to the femoral head. ### **Clinical Pearls for NEET-PG:** 1. **Avascular Necrosis (AVN):** Intracapsular fractures of the femoral neck frequently tear the retinacular branches of the **MCFA**, leading to AVN. 2. **Cruciate Anastomosis:** The MCFA and LCFA participate in the cruciate anastomosis of the thigh, connecting the internal iliac and profunda femoris systems. 3. **Pediatric Variation:** In children, before the epiphyseal plate closes, the artery of the ligamentum teres plays a more significant role in supplying the femoral head.

Question 304: The neck of a femoral hernia is located at which anatomical landmark?

A. Saphenous opening
B. Above and medial to the pubic tubercle
C. Below and lateral to the pubic tubercle (Correct Answer)
D. Mid inguinal point

Explanation: ### Explanation The anatomical location of the neck of a femoral hernia is a high-yield concept for distinguishing it from an inguinal hernia. [1] **Why Option C is Correct:** A femoral hernia occurs when abdominal contents protrude through the **femoral ring** into the femoral canal. [1] The femoral canal is located in the most medial compartment of the femoral sheath. Anatomically, the femoral ring (the neck of the hernia) lies **below and lateral to the pubic tubercle**. This relationship is the primary clinical landmark used to differentiate it from an inguinal hernia. [1] **Analysis of Incorrect Options:** * **Option A (Saphenous opening):** This is where the femoral hernia becomes superficial after passing through the femoral canal. While the hernia *presents* here, the "neck" is located deeper at the femoral ring. * **Option B (Above and medial to the pubic tubercle):** This describes the neck of an **Inguinal Hernia**. Remembering this distinction is crucial for physical examination. [1] * **Option D (Mid-inguinal point):** This is the landmark for the femoral artery (halfway between the ASIS and pubic symphysis). The femoral canal is medial to the femoral vein, making it much more medial than this point. **NEET-PG High-Yield Pearls:** 1. **Boundaries of the Femoral Ring:** Anteriorly (Inguinal ligament), Posteriorly (Pectineal ligament/Cooper’s ligament), Medially (Lacunar ligament), and Laterally (Femoral vein). 2. **Strangulation:** Femoral hernias have the highest risk of strangulation because the femoral ring is narrow and rigid (especially the sharp edge of the lacunar ligament). [1] 3. **Epidemiology:** More common in **females** due to a wider pelvis and larger femoral canal. 4. **Cloquet’s Node:** A lymph node found within the femoral canal that may be enlarged and mimic a femoral hernia.

Question 305: Venous flow in the lower limb veins in the standing position depends upon all except:

A. Arterial blood pressure (Correct Answer)
B. Presence of deep fascial planes
C. Compression of calf muscles
D. Presence of perforators

Explanation: ### Explanation Venous return from the lower limbs against gravity (in the standing position) is a complex physiological process. The correct answer is **Arterial blood pressure** because, by the time blood reaches the venous end of the capillary bed, the pressure is significantly dissipated (approx. 10–15 mmHg) [2]. This residual pressure is insufficient to overcome the hydrostatic pressure of the column of blood in a standing individual. #### Why the other options are essential for venous flow: * **Compression of calf muscles (C):** Known as the **"Peripheral Heart,"** the contraction of the gastrocnemius and soleus muscles compresses the deep veins (which are thin-walled and valved), propelling blood upward [1]. * **Presence of deep fascial planes (B):** The deep fascia (fascia lata and crural fascia) is tough and inelastic. It acts as a restrictive sleeve, ensuring that when muscles contract, the pressure is directed inward to compress the veins rather than bulging the skin outward. * **Presence of perforators (D):** These veins connect the superficial system to the deep system. They contain valves that ensure **unidirectional flow** from superficial to deep veins [1]. During muscle relaxation, they allow blood to refill the deep veins, which is then pumped upward during the next contraction. #### High-Yield Clinical Pearls for NEET-PG: * **Soleus Muscle:** Often specifically called the "Peripheral Heart" because it contains large venous sinuses (soleal sinuses) that lack valves and act as reservoirs [1]. * **Varicose Veins:** Occur due to **valvular incompetence** in the perforators or at the saphenofemoral junction, leading to the reversal of flow (deep to superficial) [3]. * **DVT (Deep Vein Thrombosis):** Stasis of blood in the soleal sinuses during prolonged immobility is a major risk factor for DVT. * **Muscle Pump Components:** The three essential components are the **muscles** (power), **valves** (direction), and **deep fascia** (containment).

Question 306: Which of the following is true about attachments at the ischial tuberosity?

A. Origin of semitendinosus from the superolateral area
B. Origin of semimembranosus from the superolateral area (Correct Answer)
C. Origin of the long head of biceps from the superolateral area
D. Origin of the adductor magnus from the superolateral area

Explanation: The **ischial tuberosity** is a critical high-yield landmark in lower limb anatomy, serving as the primary origin for the "hamstring" muscles. To master this, the tuberosity is divided into upper and lower functional areas by a transverse ridge. ### 1. Analysis of the Correct Option The **upper (superior) area** is further divided by an oblique ridge into two parts: * **Superolateral area:** This gives origin to the **semimembranosus** muscle. * **Inferomedial area:** This provides a common origin for the **long head of biceps femoris** and the **semitendinosus**. Therefore, **Option B** is correct as the semimembranosus specifically arises from the superolateral aspect of the upper part. ### 2. Analysis of Incorrect Options * **Options A & C:** Both the **semitendinosus** and the **long head of biceps femoris** originate from the **inferomedial** part of the upper area, not the superolateral area. * **Option D:** The **adductor magnus (ischiocondylar/hamstring part)** originates from the **lateral part of the lower area** of the ischial tuberosity. ### 3. NEET-PG High-Yield Clinical Pearls * **The "True" Hamstrings:** To be a true hamstring, a muscle must originate from the ischial tuberosity, be supplied by the tibial nerve, and cross both the hip and knee joints. (Note: The short head of biceps is *not* a true hamstring). * **Avulsion Fractures:** In athletic adolescents, forceful contraction of the hamstrings can lead to an avulsion fracture of the ischial tuberosity. * **Weaver’s Bottom:** Inflammation of the ischial bursa (located between the gluteus maximus and the tuberosity) is known as ischial bursitis, often caused by prolonged sitting on hard surfaces. * **Nerve Relation:** The **sciatic nerve** lies lateral to the ischial tuberosity as it descends into the thigh.

Question 307: Which nerve is most likely to be injured in a posterior dislocation of the hip joint?

A. Superior gluteal nerve
B. Inferior gluteal nerve
C. Sciatic nerve (Correct Answer)
D. Pudendal nerve

Explanation: **Explanation:** **1. Why the Sciatic Nerve is the Correct Answer:** The **sciatic nerve** is the largest nerve in the body and exits the pelvis through the greater sciatic foramen, passing directly **posterior** to the acetabulum and the hip joint. In a posterior dislocation (the most common type of hip dislocation, often due to "dashboard injuries"), the head of the femur is forced out of the acetabulum in a backward direction [1]. This displacement puts direct pressure on or causes a traction injury to the sciatic nerve [1]. Approximately 10–15% of posterior hip dislocations are associated with sciatic nerve palsy, most commonly affecting the **common peroneal division**. **2. Why the Other Options are Incorrect:** * **Superior Gluteal Nerve (A):** This nerve exits the greater sciatic foramen *above* the piriformis muscle. While it is posterior to the hip, it is situated too superiorly to be the primary nerve injured during a standard posterior dislocation. * **Inferior Gluteal Nerve (B):** This nerve exits *below* the piriformis but is primarily distributed to the gluteus maximus. While it is in the vicinity, it is less frequently involved than the massive sciatic nerve trunk. * **Pudendal Nerve (D):** This nerve exits the pelvis and immediately enters the perineum via the lesser sciatic foramen. It is located more medially and is protected by the sacrospinous ligament, making it an unlikely candidate for injury in hip dislocations. **3. NEET-PG High-Yield Pearls:** * **Mechanism:** Posterior dislocation typically occurs when the hip is **flexed, adducted, and internally rotated** (e.g., knees hitting the dashboard) [1]. * **Clinical Presentation:** The limb appears **shortened, adducted, and internally rotated** [1] (Contrast this with a neck of femur fracture, where the limb is externally rotated). * **Nerve Component:** If the sciatic nerve is injured, the **common peroneal (fibular) division** is more susceptible than the tibial division, leading to foot drop. * **Complication:** Avascular necrosis (AVN) of the femoral head is a critical late complication due to disruption of the retrograde blood supply (medial circumflex femoral artery) [1].

Question 308: The ischial tuberosity provides attachment to which muscle?

A. Obturator internus
B. Quadratus femoris
C. Gluteus maximus
D. Adductor magnus (Correct Answer)

Explanation: **Explanation:** The **ischial tuberosity** is a large, bony swelling on the posterior part of the superior ramus of the ischium. It serves as a major site for muscle attachments, specifically the "hamstring" group and the adductor magnus. **Why Adductor Magnus is correct:** The Adductor Magnus is a hybrid muscle consisting of two parts. The **Ischial (Hamstring) part** originates directly from the inferolateral part of the ischial tuberosity. It is often tested in NEET-PG because it shares the same origin and nerve supply (tibial part of the sciatic nerve) as the true hamstrings. **Analysis of Incorrect Options:** * **Obturator internus:** It originates from the internal surface of the obturator membrane and the surrounding bony margins of the obturator foramen, not the tuberosity. Its tendon passes through the lesser sciatic notch. * **Quadratus femoris:** It originates from the **lateral border** of the ischial tuberosity (just above the hamstring origin) and inserts into the quadrate tubercle of the femur. While close, it is distinct from the main tuberosity surface. * **Gluteus maximus:** It originates from the gluteal surface of the ilium, sacrum, and coccyx. It does not originate from the ischial tuberosity; rather, it **covers** the tuberosity when the hip is extended. **High-Yield Clinical Pearls for NEET-PG:** * **Hamstring Origin:** The ischial tuberosity is the common origin for Semitendinosus, Semimembranosus, and the Long head of Biceps Femoris. * **Weaver’s Bottom:** Inflammation of the ischial bursa (located between the gluteus maximus and the ischial tuberosity) is known as Ischial Bursitis. * **Pudendal Nerve:** The pudendal nerve and internal pudendal vessels pass medial to the ischial tuberosity as they enter the pudendal (Alcock’s) canal.

Question 309: A young patient presents with loss of sensation in the sole of the foot and paralysis of the medial side of the plantar muscles of the foot. Most likely nerve involvement is?

A. Common peroneal nerve
B. Deep peroneal nerve
C. Superficial peroneal nerve
D. Tibial nerve (Correct Answer)

Explanation: ### Explanation **1. Why Tibial Nerve is Correct:** The **Tibial nerve** (a branch of the Sciatic nerve) descends through the popliteal fossa and passes behind the medial malleolus into the foot. It terminates by dividing into the **Medial and Lateral Plantar nerves**. * **Sensory:** These branches provide cutaneous innervation to the entire **sole (plantar surface)** of the foot. * **Motor:** They supply all the intrinsic muscles of the sole. Therefore, a lesion of the Tibial nerve (specifically at or above the tarsal tunnel) results in sensory loss on the sole and paralysis of the plantar muscles. **2. Why Other Options are Incorrect:** * **Common Peroneal Nerve (CPN):** This nerve supplies the anterior and lateral compartments of the leg. Injury leads to "Foot Drop" and sensory loss on the dorsum of the foot, not the sole. * **Deep Peroneal Nerve:** A branch of the CPN, it supplies the anterior compartment muscles (dorsiflexors) and the skin of the **first web space**. It does not supply the sole. * **Superficial Peroneal Nerve:** Also a branch of the CPN, it supplies the peroneal muscles (evertors) and the skin of the majority of the **dorsum of the foot**. **3. Clinical Pearls for NEET-PG:** * **Tarsal Tunnel Syndrome:** Compression of the Tibial nerve behind the medial malleolus, leading to pain and paresthesia in the sole. * **Reflex:** The Tibial nerve mediates the **Ankle Jerk (S1, S2)**. * **Mnemonic for Sole Innervation:** The Medial Plantar nerve is analogous to the Median nerve in the hand (supplies 1st lumbrical and thenar-like muscles), while the Lateral Plantar nerve is like the Ulnar nerve. * **Injury Site:** The Tibial nerve is most commonly injured by deep lacerations in the popliteal fossa or posterior dislocations of the knee.

Question 310: Which neurovascular structure passes through both the greater and lesser sciatic foramen?

A. Pudendal nerve (Correct Answer)
B. Sciatic nerve
C. Superior gluteal nerve
D. Inferior gluteal nerve

Explanation: The pelvic outlet is divided by the sacrospinous and sacrotuberous ligaments into the **greater sciatic foramen (GSF)** and **lesser sciatic foramen (LSF)**. The GSF serves as the exit from the pelvis to the gluteal region, while the LSF serves as the entrance from the gluteal region to the perineum. ### Why the Pudendal Nerve is Correct The **Pudendal nerve** (S2-S4) and the **Internal pudendal vessels** follow a unique "hook-like" course. They exit the pelvis through the GSF (inferior to the piriformis muscle), cross the ischial spine, and immediately re-enter the pelvis through the LSF to reach the perineum via Alcock’s canal. *Note: The Nerve to the Obturator Internus also follows this specific path.* ### Why Other Options are Incorrect * **Sciatic Nerve:** The largest nerve in the body; it exits the pelvis through the GSF (inferior to piriformis) and continues down the posterior thigh. It **does not** re-enter the LSF. * **Superior Gluteal Nerve:** Exits the GSF **above** the piriformis muscle to supply the gluteus medius, minimus, and tensor fasciae latae. * **Inferior Gluteal Nerve:** Exits the GSF **below** the piriformis to supply the gluteus maximus. ### NEET-PG High-Yield Pearls * **The "PIN" Mnemonic:** Structures passing through both GSF and LSF are the **P**udendal nerve, **I**nternal pudendal vessels, and **N**erve to obturator internus. * **Piriformis Muscle:** Known as the "Key to the Gluteal Region" because it divides the GSF into supra-piriform and infra-piriform compartments. * **Clinical Correlation:** The pudendal nerve is targeted for a **Pudendal Nerve Block** during vaginal delivery; the landmark used is the **ischial spine**, where the nerve passes between the two foramina.

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Lower Limb — MCQs

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