A 37-year-old man is brought to the emergency department after being attacked with a knife. Physical examination shows a 4-cm laceration in the midline of the right forearm. An MRI of the right arm shows damage to a nerve that runs between the superficial and deep flexor digitorum muscles. Loss of sensation over which of the following areas is most likely in this patient?
Q72
A 3629-g (8-lb) newborn is examined shortly after spontaneous vaginal delivery. She was delivered at 40 weeks' gestation and pregnancy was uncomplicated. Her mother is concerned because she is not moving her left arm as much as her right arm. Physical examination shows her left arm to be adducted and internally rotated, with the forearm extended and pronated, and the wrist flexed. The Moro reflex is present on the right side but absent on the left side. Which of the following brachial plexus structures is most likely injured in this infant?
Q73
An 8-year-old boy is brought to the emergency department after falling from a trampoline and landing on his left arm. On presentation, he is found to be holding his left arm against his chest and says that his arm is extremely painful just above the elbow. Radiographs are obtained showing the finding in figure A. The boy's arm is reduced and placed into a splint pending surgical fixation. If this patient's fracture is associated with a nerve injury, which of the following actions would he most likely be unable to perform in the emergency department?
Q74
An 18-year-old man comes to the physician because of severe left shoulder pain after a basketball match. During the game, the patient sustained an injury to the posterior part of his outstretched arm after being blocked by a defender. Examination shows no gross deformity of the left shoulder. Palpation of the shoulder elicits mild tenderness. Internal rotation of the arm against resistance shows weakness. These findings are most specific for injury to which of the following muscles?
Q75
A 44-year-old woman comes to the physician for the evaluation of right knee pain for 1 week. The pain began after the patient twisted her knee during basketball practice. At the time of the injury, she felt a popping sensation and her knee became swollen over the next few hours. The pain is exacerbated by walking up or down stairs and worsens throughout the day. She also reports occasional locking of the knee. She has been taking acetaminophen during the past week, but the pain is worse today. Her mother has rheumatoid arthritis. The patient is 155 cm (4 ft 11 in) tall and weighs 75 kg (165 lb); BMI is 33 kg/m2. Vital signs are within normal limits. Examination shows effusion of the right knee; range of motion is limited by pain. There is medial joint line tenderness. Knee extension with rotation results in an audible snap. Further evaluation is most likely to show which of the following?
Q76
A 16-year-old girl presents with episodes of sharp pain in her left upper limb. She says her symptoms gradually onset a few months ago and have progressively worsened. She describes her pain as severe and feeling like “someone stabbing me in my arm and then the pain moves down to my hand”. She says the pain is worse after physical activity and improves with rest. She also says she has some vision problems in her left eye. The patient is afebrile, and her vital signs are within normal limits. On physical examination, there are no visible deformities in the shoulders or upper extremities. Palpation of her left upper limb reveals tenderness mainly near her neck. Mild left-sided ptosis is present. There is anisocoria of her left pupil which measures 1 mm smaller than the right. The right upper limb is normal. A plain radiograph and an MRI are ordered (shown in the image). Which of the following focal neurologic deficits would most likely be seen on the left hand of this patient?
Q77
A 72-year-old woman presents with left lower limb swelling. She first noticed her left leg was swollen about 2 weeks ago. She denies any pain and initially thought the swelling would subside on its own. Past medical history is significant for hypertension and hyperlipidemia. She is a smoker with a 35 pack-year history and an occasional drinker. She takes chlorthalidone, lisinopril, atorvastatin and a multivitamin. On physical examination, her left leg appears larger than her right with 2+ pitting edema up to her knee. She also has a few distended superficial veins along the posterior aspect of her left leg. Lower extremities have 2+ pulses bilaterally. The ultrasound of her left lower thigh and leg shows an obstructing thrombosis of the distal portion of the femoral vein. Which of the following veins serve as collateral pathways to help mitigate the consequences of this patient's condition?
Q78
A 61-year-old woman comes to the physician for a follow-up examination 1 week after undergoing right-sided radical mastectomy and axillary lymph node dissection for breast cancer. She says that she has been unable to comb her hair with her right hand since the surgery. Physical examination shows shoulder asymmetry. She is unable to abduct her right arm above 90 degrees. When she pushes against a wall, there is protrusion of the medial aspect of the right scapula. Injury to which of the following nerves is the most likely cause of this patient's condition?
Q79
A 19-year-old collegiate football player sustains an injury to his left knee during a game. He was running with the ball when he dodged a defensive player and fell, twisting his left knee. He felt a “pop” as he fell. When he attempts to bear weight on his left knee, it feels unstable, and "gives way." He needs assistance to walk off the field. The pain is localized diffusely over the knee and is non-radiating. His past medical history is notable for asthma. He uses an albuterol inhaler as needed. He does not smoke or drink alcohol. On exam, he has a notable suprapatellar effusion. Range of motion is limited in the extremes of flexion. When the proximal tibia is pulled anteriorly while the knee is flexed and the patient is supine, there is 1.5 centimeter of anterior translation. The contralateral knee translates 0.5 centimeters with a similar force. The injured structure in this patient originates on which of the following bony landmarks?
Q80
A 45-year-old male presents to his primary care provider with an abnormal gait. He was hospitalized one week prior for acute cholecystitis and underwent a laparoscopic cholecystectomy. He received post-operative antibiotics via intramuscular injection. He recovered well and he was discharged on post-operative day #3. However, since he started walking after the operation, he noticed a limp that has not improved. On exam, his left hip drops every time he raises his left foot to take a step. In which of the following locations did this patient likely receive the intramuscular injection?
Upper/Lower Limb US Medical PG Practice Questions and MCQs
Question 71: A 37-year-old man is brought to the emergency department after being attacked with a knife. Physical examination shows a 4-cm laceration in the midline of the right forearm. An MRI of the right arm shows damage to a nerve that runs between the superficial and deep flexor digitorum muscles. Loss of sensation over which of the following areas is most likely in this patient?
A. Medial aspect of the forearm
B. Fingertip of the index finger (Correct Answer)
C. Dorsum of the thumb
D. Palmar surface of the little finger
E. Lateral aspect of the forearm
Explanation: ***Fingertip of the index finger***
- The nerve running between the superficial and deep **flexor digitorum muscles** in the forearm is the **median nerve**.
- The median nerve supplies sensation to the **palmar aspect of the thumb, index, middle, and radial half of the ring finger**, including their fingertips.
*Medial aspect of the forearm*
- Sensation to the medial aspect of the forearm is primarily supplied by the **medial antebrachial cutaneous nerve**, a branch of the brachial plexus.
- This nerve is located superficially and is not typically associated with the deep flexor muscles.
*Dorsum of the thumb*
- The dorsum of the thumb is primarily innervated by the **radial nerve** and its superficial branch.
- The median nerve's sensory distribution does not extend to the dorsum of the thumb.
*Palmar surface of the little finger*
- Sensation to the palmar surface of the little finger is supplied by the **ulnar nerve**.
- The ulnar nerve runs medial to the median nerve and innervates the ulnar side of the hand.
*Lateral aspect of the forearm*
- Sensation to the lateral aspect of the forearm is mainly supplied by the **lateral antebrachial cutaneous nerve**, which is a continuation of the musculocutaneous nerve.
- This area is generally not affected by median nerve injuries in the forearm.
Question 72: A 3629-g (8-lb) newborn is examined shortly after spontaneous vaginal delivery. She was delivered at 40 weeks' gestation and pregnancy was uncomplicated. Her mother is concerned because she is not moving her left arm as much as her right arm. Physical examination shows her left arm to be adducted and internally rotated, with the forearm extended and pronated, and the wrist flexed. The Moro reflex is present on the right side but absent on the left side. Which of the following brachial plexus structures is most likely injured in this infant?
A. Upper trunk (Correct Answer)
B. Axillary nerve
C. Lower trunk
D. Long thoracic nerve
E. Posterior cord
Explanation: ***Upper trunk***
- The symptoms described, including the arm being **adducted, internally rotated**, with the forearm extended and pronated, and a **flexed wrist**, are characteristic of **Erb-Duchenne palsy**, an injury to the **upper trunk** of the brachial plexus (C5-C6 nerve roots).
- The absence of the **Moro reflex** on the affected side further indicates an injury to the **upper brachial plexus**, as these roots contribute to the reflex arc.
*Axillary nerve*
- An injury to the **axillary nerve** would primarily affect the **deltoid** and **teres minor muscles**, leading to weakness in **shoulder abduction** and external rotation.
- While shoulder abduction is impaired in this case, the more widespread deficits affecting multiple arm movements point to a more proximal brachial plexus injury rather than an isolated axillary nerve lesion.
*Lower trunk*
- Injury to the **lower trunk** (C8-T1 nerve roots) typically results in **Klumpke's palsy**, characterized by weakness or paralysis of the **intrinsic hand muscles** and **flexors of the wrist and fingers**, leading to a "claw hand" deformity.
- The described presentation does not align with the classic features of Klumpke's palsy.
*Long thoracic nerve*
- An injury to the **long thoracic nerve** would cause **paralysis of the serratus anterior muscle**, leading to **scapular winging** (the medial border of the scapula protruding posteriorly, especially when pushing against a wall).
- This symptom is not described in the patient's presentation.
*Posterior cord*
- The **posterior cord** gives rise to the axillary and radial nerves. Injury to the posterior cord would affect muscles innervated by these nerves, including the **deltoid, triceps**, and **extensors of the wrist and fingers**.
- While some of these movements (e.g., forearm extension) are affected, the specific "waiter's tip" posture strongly points to an upper trunk injury, which involves a broader distribution of muscles than just those supplied by the posterior cord.
Question 73: An 8-year-old boy is brought to the emergency department after falling from a trampoline and landing on his left arm. On presentation, he is found to be holding his left arm against his chest and says that his arm is extremely painful just above the elbow. Radiographs are obtained showing the finding in figure A. The boy's arm is reduced and placed into a splint pending surgical fixation. If this patient's fracture is associated with a nerve injury, which of the following actions would he most likely be unable to perform in the emergency department?
A. Elbow flexion
B. Finger extension
C. Finger crossing
D. Shoulder abduction
E. Thumb flexion (Correct Answer)
Explanation: ***Thumb flexion***
- This clinical scenario describes a **supracondylar humerus fracture**, the most common elbow fracture in children and the most commonly injured nerve is the **anterior interosseous nerve (AIN)**, a branch of the median nerve.
- The **AIN** innervates the **flexor pollicis longus (FPL)**, which is responsible for **flexion of the thumb interphalangeal (IP) joint**.
- Injury to the AIN results in **inability to flex the thumb tip**, which is tested by having the patient make an "OK" sign - they cannot form a circle with thumb and index finger.
- This makes **thumb flexion** the most likely impaired action in this scenario.
*Elbow flexion*
- **Elbow flexion** is primarily mediated by the **musculocutaneous nerve** (supplying biceps and brachialis) and the radial nerve (supplying brachioradialis).
- These nerves are not typically injured in supracondylar humerus fractures.
*Finger extension*
- **Finger extension** is controlled by the **radial nerve** via the posterior interosseous nerve.
- While radial nerve injury can occur with supracondylar fractures (second most common nerve injury), it is less frequent than **AIN injury**.
*Finger crossing*
- **Finger crossing** (adduction and abduction of fingers) is controlled by the **ulnar nerve**, which innervates the interossei muscles.
- Ulnar nerve injury is the least common nerve complication of supracondylar fractures.
*Shoulder abduction*
- **Shoulder abduction** is controlled by the **deltoid muscle**, innervated by the **axillary nerve**.
- The axillary nerve originates from the proximal brachial plexus and is not involved in elbow-region injuries.
Question 74: An 18-year-old man comes to the physician because of severe left shoulder pain after a basketball match. During the game, the patient sustained an injury to the posterior part of his outstretched arm after being blocked by a defender. Examination shows no gross deformity of the left shoulder. Palpation of the shoulder elicits mild tenderness. Internal rotation of the arm against resistance shows weakness. These findings are most specific for injury to which of the following muscles?
A. Infraspinatus
B. Deltoid
C. Supraspinatus
D. Teres minor
E. Subscapularis (Correct Answer)
Explanation: ***Subscapularis***
- The **subscapularis** is the primary muscle responsible for **internal rotation** of the arm. Weakness in this movement against resistance is a key indicator of its injury.
- Injury can occur with a **sudden force** applied to an **outstretched arm**, especially with a posterior impact, as this can force the humerus into excessive external rotation and anterior translation, tearing the subscapularis.
*Infraspinatus*
- The **infraspinatus** is primarily involved in **external rotation** of the arm; its injury would lead to weakness in external rotation, not internal rotation.
- It also assists in **shoulder abduction**, but its main isolated action is external rotation.
*Deltoid*
- The **deltoid** muscle is the main abductor of the arm and also assists in **flexion and extension**, depending on which fibers are active.
- Injury to the deltoid would typically result in weakness with **arm abduction** and possibly a visible deformity, which is not noted here.
*Supraspinatus*
- The **supraspinatus** is primarily responsible for the **initiation of arm abduction** (first 15-20 degrees) and stabilizing the humeral head.
- While it is a common rotator cuff injury, its damage would manifest as pain and weakness during abduction, not internal rotation.
*Teres minor*
- The **teres minor** is another muscle involved in **external rotation** of the arm and also helps to stabilize the shoulder joint.
- Its injury would present with weakness in external rotation, similar to the infraspinatus, and not internal rotation.
Question 75: A 44-year-old woman comes to the physician for the evaluation of right knee pain for 1 week. The pain began after the patient twisted her knee during basketball practice. At the time of the injury, she felt a popping sensation and her knee became swollen over the next few hours. The pain is exacerbated by walking up or down stairs and worsens throughout the day. She also reports occasional locking of the knee. She has been taking acetaminophen during the past week, but the pain is worse today. Her mother has rheumatoid arthritis. The patient is 155 cm (4 ft 11 in) tall and weighs 75 kg (165 lb); BMI is 33 kg/m2. Vital signs are within normal limits. Examination shows effusion of the right knee; range of motion is limited by pain. There is medial joint line tenderness. Knee extension with rotation results in an audible snap. Further evaluation is most likely to show which of the following?
A. Hyperintense line in the meniscus on MRI (Correct Answer)
B. Trabecular loss in the proximal femur on x-ray
C. Posterior tibial translation on examination
D. Erosions and synovial hyperplasia on MRI
E. Anterior tibial translation on examination
Explanation: ***Hyperintense line in the meniscus on MRI***
- This patient's symptoms of a **popping sensation**, rapid swelling, pain with stairs, and **locking of the knee** after a twisting injury are highly suggestive of a **meniscal tear**.
- An MRI with a **hyperintense line within the substance of the meniscus extending to the articular surface** is the classic finding for a meniscal tear.
*Trabecular loss in the proximal femur on x-ray*
- **Trabecular loss** in the proximal femur on X-ray is characteristic of **osteoporosis**, a condition affecting bone density.
- While this patient is a woman, there are no other clinical signs pointing to osteoporosis, and it would not explain the acute knee injury symptoms.
*Posterior tibial translation on examination*
- **Posterior tibial translation** on examination (positive posterior drawer test) indicates damage to the **posterior cruciate ligament (PCL)**.
- While a knee injury, the symptoms of initial popping, rapid swelling, and locking are more characteristic of a meniscal tear or ACL injury than an isolated PCL tear.
*Erosions and synovial hyperplasia on MRI*
- **Erosions and synovial hyperplasia** on MRI are classic findings in **inflammatory arthropathies** like **rheumatoid arthritis**, which primarily affect the joint lining (synovium).
- Although the patient's mother has rheumatoid arthritis, there is no indication of chronic inflammatory arthritis, and the patient's acute injury symptoms are not consistent with this.
*Anterior tibial translation on examination*
- **Anterior tibial translation** on examination (positive anterior drawer test or Lachman test) indicates damage to the **anterior cruciate ligament (ACL)**.
- While an ACL injury can cause a pop and swelling, the prominent symptom of **locking** is more specifically associated with meniscal tears where a torn piece of cartilage intermittently blocks joint movement.
Question 76: A 16-year-old girl presents with episodes of sharp pain in her left upper limb. She says her symptoms gradually onset a few months ago and have progressively worsened. She describes her pain as severe and feeling like “someone stabbing me in my arm and then the pain moves down to my hand”. She says the pain is worse after physical activity and improves with rest. She also says she has some vision problems in her left eye. The patient is afebrile, and her vital signs are within normal limits. On physical examination, there are no visible deformities in the shoulders or upper extremities. Palpation of her left upper limb reveals tenderness mainly near her neck. Mild left-sided ptosis is present. There is anisocoria of her left pupil which measures 1 mm smaller than the right. The right upper limb is normal. A plain radiograph and an MRI are ordered (shown in the image). Which of the following focal neurologic deficits would most likely be seen on the left hand of this patient?
A. Numbness over the thenar area of her left hand
B. Numbness over her left thumb
C. Numbness over her left little finger (Correct Answer)
D. Numbness over her left index finger
E. Numbness over the dorsal aspect of her left hand
Explanation: ***Numbness over her left little finger***
- The patient's symptoms, including sharp upper limb pain, worsening with activity, vision problems in the left eye, mild left-sided ptosis, and left pupillary anisocoria, are highly suggestive of **Pancoast tumor**.
- A Pancoast tumor, located in the **superior sulcus of the lung**, often involves the lower trunk of the **brachial plexus (C8-T1 nerve roots)**, leading to sensory deficits in the distribution of the **ulnar nerve**, which supplies the little finger.
*Numbness over the thenar area of her left hand*
- Numbness in the thenar area is primarily associated with **median nerve** innervation, typically from **C5-C7 nerve roots**.
- While a Pancoast tumor can affect various parts of the brachial plexus, the presence of **Horner's syndrome** (ptosis, miosis, anhidrosis) strongly points to **T1 involvement**, making ulnar nerve distribution (C8-T1) more likely.
*Numbness over her left thumb*
- Sensory innervation of the thumb is primarily by the **median nerve (C6-C7)**, with some contribution from the radial nerve.
- This distribution would be less common with the specific constellation of symptoms, especially the oculosympathetic involvement, which points to **C8-T1 nerve root damage**.
*Numbness over her left index finger*
- The index finger receives sensory innervation predominantly from the **median nerve (C6-C7)**.
- The clinical presentation, particularly the Horner's syndrome pointing to **T1 nerve root involvement**, makes sensory deficits in the ulnar nerve distribution (C8-T1) more probable than those of the median nerve.
*Numbness over the dorsal aspect of her left hand*
- The dorsal aspect of the hand is primarily innervated by the **radial nerve (C5-C7)** and superficial branch of the radial nerve.
- This distribution does not align with the patient's presentation of **C8-T1 nerve root involvement** from the Pancoast tumor affecting the lower trunk of the brachial plexus.
Question 77: A 72-year-old woman presents with left lower limb swelling. She first noticed her left leg was swollen about 2 weeks ago. She denies any pain and initially thought the swelling would subside on its own. Past medical history is significant for hypertension and hyperlipidemia. She is a smoker with a 35 pack-year history and an occasional drinker. She takes chlorthalidone, lisinopril, atorvastatin and a multivitamin. On physical examination, her left leg appears larger than her right with 2+ pitting edema up to her knee. She also has a few distended superficial veins along the posterior aspect of her left leg. Lower extremities have 2+ pulses bilaterally. The ultrasound of her left lower thigh and leg shows an obstructing thrombosis of the distal portion of the femoral vein. Which of the following veins serve as collateral pathways to help mitigate the consequences of this patient's condition?
A. Giacomini vein
B. Fibular vein
C. Accessory saphenous vein
D. Perforator veins (Correct Answer)
E. Deep femoral vein
Explanation: ***Perforator veins***
- **Perforator veins** connect the **superficial venous system** to the **deep venous system**, normally allowing blood to flow from superficial to deep veins through one-way valves.
- In cases of **deep vein thrombosis (DVT)**, when the deep venous system is obstructed, these veins can serve as **important collateral pathways**, allowing blood to be rerouted from the obstructed deep system to the superficial system, thereby preventing excessive venous engorgement and helping to reduce severe edema.
- This explains the **distended superficial veins** seen on examination in this patient—blood is being diverted through perforators to the superficial system.
*Giacomini vein*
- The **Giacomini vein** is a **superficial vein** connecting the small saphenous vein to the great saphenous vein, typically in the popliteal fossa and posterior thigh.
- It primarily shunts blood within the **superficial system** and does not provide significant collateral drainage when the deep venous system is occluded.
*Fibular vein*
- The **fibular vein** (also known as the peroneal vein) is a **deep vein** of the lower leg, running alongside the fibula and draining into the posterior tibial veins.
- While it is part of the deep venous system, the thrombosis in this case is in the **femoral vein** (more proximal), so the fibular vein would drain into the same obstructed system rather than serving as a bypass collateral.
*Accessory saphenous vein*
- The **accessory saphenous vein** is a **superficial vein** that runs parallel to and is a tributary of the great saphenous vein in the thigh.
- It is part of the superficial system and does not provide a collateral pathway **from** the obstructed deep system, though it may carry increased flow if perforators are diverting blood to the superficial system.
*Deep femoral vein*
- The **deep femoral vein** (profunda femoris vein) is a **deep vein** that drains the deep compartments of the thigh and joins the common femoral vein.
- While it can provide some collateral drainage when the superficial femoral vein (femoral vein) is occluded, it ultimately drains into the **same deep venous system** proximally and is not the primary collateral mechanism connecting superficial and deep systems.
Question 78: A 61-year-old woman comes to the physician for a follow-up examination 1 week after undergoing right-sided radical mastectomy and axillary lymph node dissection for breast cancer. She says that she has been unable to comb her hair with her right hand since the surgery. Physical examination shows shoulder asymmetry. She is unable to abduct her right arm above 90 degrees. When she pushes against a wall, there is protrusion of the medial aspect of the right scapula. Injury to which of the following nerves is the most likely cause of this patient's condition?
A. Long thoracic nerve (Correct Answer)
B. Thoracodorsal nerve
C. Axillary nerve
D. Suprascapular nerve
E. Upper trunk of the brachial plexus
Explanation: ***Long thoracic nerve***
- Injury to the **long thoracic nerve** leads to paralysis of the **serratus anterior muscle**, causing **scapular winging** (protrusion of the medial scapula) especially when pushing against a wall.
- The serratus anterior is crucial for **scapular protraction** and stabilizing the scapula during **abduction of the arm above 90 degrees**, explaining her inability to comb her hair.
*Thoracodorsal nerve*
- The **thoracodorsal nerve** innervates the **latissimus dorsi muscle**, which is responsible for **adduction**, extension, and internal rotation of the arm.
- Injury to this nerve would primarily affect these movements, not shoulder abduction above 90 degrees or scapular winging.
*Axillary nerve*
- The **axillary nerve** innervates the **deltoid muscle** and **teres minor**.
- Damage would primarily result in impaired **arm abduction up to 90 degrees** and loss of sensation over the lateral shoulder, but not scapular winging.
*Suprascapular nerve*
- The **suprascapular nerve** supplies the **supraspinatus** and **infraspinatus muscles**, which are involved in the initiation of arm abduction and external rotation, respectively.
- Injury would cause weakness in these movements and shoulder pain, but not scapular winging.
*Upper trunk of the brachial plexus*
- Injury to the **upper trunk of the brachial plexus** (C5-C6) affects several nerves and muscles, leading to conditions like **Erb's palsy**.
- While it can impair shoulder function and abduction, the specific finding of scapular winging points more directly to long thoracic nerve damage rather than a generalized upper trunk injury, as the long thoracic nerve (C5-C7) is often spared in classic Erb's palsy.
Question 79: A 19-year-old collegiate football player sustains an injury to his left knee during a game. He was running with the ball when he dodged a defensive player and fell, twisting his left knee. He felt a “pop” as he fell. When he attempts to bear weight on his left knee, it feels unstable, and "gives way." He needs assistance to walk off the field. The pain is localized diffusely over the knee and is non-radiating. His past medical history is notable for asthma. He uses an albuterol inhaler as needed. He does not smoke or drink alcohol. On exam, he has a notable suprapatellar effusion. Range of motion is limited in the extremes of flexion. When the proximal tibia is pulled anteriorly while the knee is flexed and the patient is supine, there is 1.5 centimeter of anterior translation. The contralateral knee translates 0.5 centimeters with a similar force. The injured structure in this patient originates on which of the following bony landmarks?
A. Posteromedial aspect of the lateral femoral condyle (Correct Answer)
B. Lateral aspect of the lateral femoral condyle
C. Lateral aspect of the medial femoral condyle
D. Tibial tubercle
E. Medial aspect of the medial femoral condyle
Explanation: ***Posteromedial aspect of the lateral femoral condyle***
- The patient's presentation of a **\"pop\"**, knee instability, and a **positive anterior drawer test** (excessive anterior translation of the tibia) strongly indicates an **anterior cruciate ligament (ACL) tear**.
- The **ACL originates** from the **posteromedial aspect of the lateral femoral condyle** and inserts onto the anterior intercondylar area of the tibia.
*Lateral aspect of the lateral femoral condyle*
- This area is typically associated with the origin of the **lateral collateral ligament (LCL)**, which would present with instability to **varus stress**, not anterior translation.
- Injuries to the LCL do not typically cause the described \"giving way\" sensation in the same manner as an ACL tear.
*Lateral aspect of the medial femoral condyle*
- The medial femoral condyle is primarily associated with the origin of the **medial collateral ligament (MCL)**.
- An MCL injury would typically present with **valgus instability** and pain on the medial side of the knee.
*Tibial tubercle*
- The tibial tubercle is the insertion point for the **patellar tendon**, which is the distal attachment of the quadriceps femoris muscle.
- Injuries here are more commonly associated with conditions like **Osgood-Schlatter disease** in adolescents or patellar tendon ruptures, not typically ACL-like instability.
*Medial aspect of the medial femoral condyle*
- This region is the primary origin for the **medial collateral ligament (MCL)**.
- MCL tears are often caused by **valgus stress** and would result in increased laxity to valgus forces, not anterior tibial translation.
Question 80: A 45-year-old male presents to his primary care provider with an abnormal gait. He was hospitalized one week prior for acute cholecystitis and underwent a laparoscopic cholecystectomy. He received post-operative antibiotics via intramuscular injection. He recovered well and he was discharged on post-operative day #3. However, since he started walking after the operation, he noticed a limp that has not improved. On exam, his left hip drops every time he raises his left foot to take a step. In which of the following locations did this patient likely receive the intramuscular injection?
A. Superomedial quadrant of the buttock (Correct Answer)
B. Superolateral quadrant of the buttock
C. Anteromedial thigh
D. Inferomedial quadrant of the buttock
E. Inferolateral quadrant of the buttock
Explanation: ***Superomedial quadrant of the buttock***
- An injection in the **superomedial quadrant of the buttock** is the most common site for iatrogenic injury to the **superior gluteal nerve**.
- The superior gluteal nerve exits the pelvis through the greater sciatic foramen above the piriformis muscle and runs in the **superomedial** region of the buttock.
- Injury to the superior gluteal nerve results in weakness of the **gluteus medius and minimus muscles**, leading to a **Trendelenburg gait** (hip drops on the contralateral side when lifting that leg), which is consistent with the patient's symptoms.
- This is why the **superolateral quadrant** is recommended for safe IM injections.
*Superolateral quadrant of the buttock*
- The **superolateral quadrant** is the **safest site** for intramuscular gluteal injections precisely because it avoids the superior gluteal nerve.
- This is the recommended injection site to prevent the complication that this patient experienced.
- An injection here would not cause superior gluteal nerve injury or Trendelenburg gait.
*Inferomedial quadrant of the buttock*
- Injections in the **inferomedial quadrant** put the **sciatic nerve** at significant risk of injury.
- Sciatic nerve injury would lead to symptoms affecting the posterior thigh and lower leg, such as **foot drop, loss of ankle reflexes, or paresthesias in the posterior leg and foot**, not isolated hip abductor weakness.
*Inferolateral quadrant of the buttock*
- This area is close to the **sciatic nerve** and **inferior gluteal nerve**.
- Inferior gluteal nerve injury would affect the **gluteus maximus**, leading to difficulty with hip extension (trouble climbing stairs, rising from a chair), not a Trendelenburg gait.
- Sciatic nerve injury would present with foot drop and sensory deficits.
*Anteromedial thigh*
- Injections in the **anteromedial thigh** could injure the **femoral nerve** or its branches.
- This would cause **quadriceps weakness** with impaired knee extension and difficulty walking (buckling knee), not hip abductor weakness or Trendelenburg gait.
- The femoral nerve does not control hip abduction.