A 23-year-old man is brought to the emergency department after sustaining stab injuries in a street fight.  The patient feels lightheaded and dizzy.  Blood pressure is 100/60 mm Hg and pulse is 115/min.  Physical examination shows profuse bleeding from penetrating wounds over the right neck and shoulder area.  Intravenous fluids are administered, and a blood transfusion is initiated.  Urgent surgical exploration is performed, and injured blood vessels are repaired.  Further exploration shows complete transection of a specific nerve, which is indicated by the arrow in the image below:

Which of the following actions is most likely to be impaired as a result of this patient’s nerve injury?

A 45-year-old woman is evaluated for numbness and painful tingling of the right hand.  The symptoms began 2 months ago and are especially prominent after she plays tennis.  On examination, there is diminished sensation in the lateral palm, thenar eminence, and palmar aspect of the first 3½ digits of the right hand.  Electrodiagnostic studies are consistent with median neuropathy in the forearm.  This patient is most likely to have nerve compression between which of the following structures?

A 53-year-old man is evaluated for right hand discomfort.  A month ago, the patient started to experience an intermittent pins-and-needles sensation in his right hand that is worse at night.  He has no neck pain or history of trauma.  The patient has smoked a pack of cigarettes daily for 20 years and has worked as an accountant for the past 30 years.  On physical examination, there is loss of sensation over the right fifth digit.  There is no swelling, redness, or warmth of the hand.  The patient is most likely to have weakness of which of the following movements?

A 63-year-old man comes to the physician’s office due to long-standing osteoarthritis that is refractory to over-the-counter analgesics.  After discussing various treatment options with his physician, the patient is referred to a surgeon for right total hip arthroplasty.  His acute postoperative course is unremarkable.  During a follow-up appointment, the patient reports difficulty walking despite minimal pain.  On examination, he leans to his right side when walking.  When asked to stand on his right leg, the patient’s left hip tilts downward.  Which of the following nerves is most likely injured in this patient?

A 12-year-old boy is brought to the emergency department by his mother due to left hand clumsiness.  Several hours ago, he was climbing a tree but lost his balance and fell, grabbing a branch with his left hand on the way down.  He landed safely on his feet with no head injury or loss of consciousness.  On physical examination, the patient has difficulty performing fine finger movements with his left hand.  Which of the following structures is most likely injured in this patient?

A 68-year-old woman is evaluated for right lower extremity weakness while hospitalized.  The patient was admitted after sustaining a right femoral neck fracture and underwent total hip arthroplasty.  Her operative course was uncomplicated, but the patient experienced right leg weakness postoperatively.  Since the surgery, she has had difficulty with physical therapy and reports numbness of the right leg.  The patient’s other medical conditions include hypertension, type 2 diabetes mellitus, a prior transient ischemic attack, and osteoarthritis.  Right lower extremity examination shows weakness in dorsiflexion, plantar flexion, and knee flexion.  Hip flexion and knee extension are normal.  Sensation to light touch is decreased on the dorsum of the right foot and posterolateral aspect of the right calf.  Ankle reflex is absent on the right.  Which of the following is the most likely cause of this patient’s current findings?

A 69-year-old hospitalized woman is evaluated for new-onset weakness of the right foot.  The patient has a history of chronic hip pain due to osteoarthritis.  Two days ago, she underwent left total hip arthroplasty under general anesthesia while in the right lateral decubitus position.  Since the surgery, she has had difficulty moving her right foot.  Other medical conditions include lumbar spinal stenosis, hypertension, type 2 diabetes mellitus, and a small ischemic stroke with no residual deficit.  On examination of the right lower extremity, the patient is unable to dorsiflex the ankle, evert the foot, or extend the toes.  Sensation is decreased over the dorsum of the right foot.  Injury to which of the following structures is the most likely cause of this patient’s current symptoms?

A 25-year-old man comes to the office due to right arm weakness.  The patient injured his right shoulder several months ago in a motor vehicle collision and has had difficulty raising his arm since.  On examination, there is diminished pinprick and temperature sensation over a small area in the right upper lateral arm and prominent atrophy of the right deltoid with 3/5 strength on right shoulder abduction.  Reflexes and handgrip strength are normal in the upper extremities bilaterally.  This patient most likely injured which of the following nerves?

A 13-year-old boy comes to the office for a postoperative follow-up visit.  He was seen in the emergency department 3 weeks earlier with acute abdominal pain and was found to have acute appendicitis.  The patient underwent urgent appendectomy without any apparent immediate complications and was released home.  Several days later, he started having burning pain at the surgical scar radiating to the suprapubic region but otherwise feels well.  Examination shows a healed surgical incision centered over McBurney point.  There is a loss of sensation over the right suprapubic area.  The cremasteric reflex is normal.  Which of the following nerves is most likely injured in this patient?

A 15-year-old girl is brought to the hospital due to sudden onset of severe left leg pain.  She was practicing for an upcoming gymnastics competition when she felt a popping sensation after landing from a jump and developed anterior left leg pain.  Following the injury, the patient was unable to bear weight on the leg.  Physical examination shows swelling of the left knee with focal tenderness just above the patella.  She is unable to raise the left leg against gravity while in the supine position.  Imaging confirms a complete tear of the quadriceps tendon, but no fractures are identified.  Surgical repair is planned.  Lidocaine injection near which of the following sites is most likely to provide adequate anesthesia for the procedure?

A 56-year-old man is evaluated in the clinic due to worsening lower extremity pain and weakness.  The patient has had hematuria and intermittent burning on urination for the past year.  He has no history of pelvic trauma or surgery.  The patient has smoked a pack of cigarettes daily for the past 35 years.  His urine culture is negative for bacterial growth.  Urine cytology and cystoscopy confirm the diagnosis of transitional cell carcinoma.  Abdominal CT shows an advanced bladder tumor compressing a nerve that passes through the obturator canal.  Which of the following actions would most likely be impaired in this patient?

A 7-year-old boy is brought to the emergency department after injuring his right knee in a bicycle accident.  Physical examination shows a swollen right knee with abrasion of the overlying skin.  Distal motor and sensory innervation is intact, and popliteal and pedal pulses are normal.  No other significant trauma is noted.  X-ray reveals a nondisplaced patellar fracture.  The patient is referred to orthopedics and placed in a leg cylinder cast.  On follow-up a week after cast placement, he has paresthesia and numbness of the dorsum of the right foot with weakness in foot dorsiflexion and eversion.  Which of the following is the most likely site of nerve compression in this patient?

A 55-year-old man is being evaluated for a 4-week history of right shoulder pain.  The pain worsens when actively abducting the shoulder or when lying on the shoulder at night.  The patient also has weakness with abduction and external rotation of the right shoulder.  He has attempted treatment with over-the-counter analgesics with limited relief.  MRI of the shoulder shows a partial rotator cuff tear, and the patient is scheduled for surgical repair.  Immediately before the surgery, he receives anesthesia with an injection between the right anterior and middle scalene muscles in order to block the C3 through C7 nerve roots of the cervical and brachial plexuses.  Which of the following muscles is most likely to be paralyzed due to the anesthesia?

A 20-year-old man is evaluated in the clinic for right arm weakness and numbness.  He pitches for his college baseball team and threw more than usual last week due to a postseason tournament.  Since then, the patient has had difficulty using his right arm, particularly when lifting objects.  He has no history of head, neck, or upper extremity trauma.  On physical examination, there is diminished strength on right elbow flexion and an absent biceps reflex.  This patient is most likely to have sensory loss over which of the following areas?

A 43-year-old woman comes to the office due to acute back pain after dragging a heavy box.  The pain is located in her lower back and radiates down the right posterior thigh to the foot.  The patient describes the pain as “shooting” and grades it 8/10 in intensity.  She has no bowel or bladder symptoms.  The patient has tried over-the-counter analgesics with limited symptomatic relief.  Vital signs are within normal limits.  On physical examination, straight leg raise testing is positive on the right.  Right hip extension is weaker when compared to the left.  Patellar reflexes are 2+ and bilaterally symmetric, but the right Achilles reflex is absent.  Which of the following nerve roots is most likely affected in this patient?

A 25-year-old man fractures his right tibia in a motor vehicle collision.  His right leg is fixed in a cast, and he requires underarm crutches to ambulate.  Two weeks later, the patient comes to the clinic with right upper extremity weakness and numbness.  He has no neck or arm pain.  The patient is concerned because he is right handed and cannot perform his duties as an electrician.  On neurologic examination, there is diminished strength on extension of the right wrist with an absent triceps reflex.  Injury to which of the following nerves is most likely responsible for this patient’s symptoms?

A 29-year-old previously healthy man comes to the hospital with a right leg injury after a cycling accident.  He reports pain in the lower leg and inability to bear weight.  X-ray reveals right tibial and fibular shaft fractures.  The patient undergoes closed reduction and immobilization of the fractures.  Several hours later, he has increasingly severe pain in his right leg.  Physical examination shows increased tension within the anterior compartment.  Which of the following structures is most likely to be compromised by this patient’s acute complication?

A 43-year-old woman comes to the clinic due to pain and tingling in the first three digits of both hands that is worse at night, sometimes preventing her from sleeping.  She has no problems with her legs.  The patient has chronic kidney disease due to IgA nephropathy and receives hemodialysis.  On examination, she has diminished sensation in both hands over the palmar aspect of the thumb, index and middle fingers, and radial half of the ring finger.  Which of the following is the most likely underlying mechanism of this patient’s current symptoms?

A 17-year-old boy is brought to the emergency department due to a lower extremity injury.  The patient was playing football with his friends when he was tackled roughly and “felt something snap” in his right leg.  He avoids bearing weight on the right foot.  Examination shows a large contusion with point tenderness at the proximal lateral right leg.  An x-ray of the leg is shown in the exhibit.  Which of the following would most likely be found on physical examination?

A 20-year-old man comes to the hospital with knee pain after he tripped and landed on his right knee during a soccer game.  The anterior portion of his tibia impacted directly against the ground, and he has been unable to bear weight since the injury.  On physical examination, the patient’s knee appears swollen, and there is excessive posterior displacement of the tibia when pressure is applied to his anterior tibia with the knee in the flexed position.  An axial MRI cross section of the right knee at the level of the tibial plateau is shown below.  Which of the following structures is most likely injured in this patient?

A 19-year-old woman is evaluated in the clinic due to right hand clumsiness.  The patient injured the right upper extremity after falling off her bicycle 6 months ago.  She has since had a pins-and-needles sensation in her right hand that is associated with mild weakness.  The patient is worried because these symptoms interfere with her piano practice and she has a recital in 3 weeks.  Physical examination shows decreased sensation over the fifth digit and a flattened hypothenar eminence.  Triceps reflexes are 2+ and symmetric bilaterally.  The nerve affected in this patient is likely to be injured at which of the following locations?

A 3-year-old boy is brought to the emergency department for refusal to move his right arm.  This afternoon, he tripped while holding hands with his sister, who pulled up on his arm to prevent him from falling.  The patient immediately began to cry and has since refused to move the arm.  On physical examination, he holds the right arm against his abdomen with the elbow flexed and forearm pronated.  The patient cries with any attempted manipulation of the right elbow.  There is no visible swelling or deformity.  Which of the following structures is most likely affected in this patient’s condition?

A 46-year-old gardener comes to the office due to knee pain.  It began abruptly 3 days earlier and improved only minimally with acetaminophen.  The patient spends hours on his knees several times a week while working.  Past medical history is notable for hypertension and seasonal allergies.  His current medications include lisinopril, loratadine, and fluticasone nasal spray.  Examination of the lower extremity shows no visible erythema or abrasions, but there is sharp, localized pain on palpation.  Passive range of motion is normal in all joints, but the patient has severe pain when walking around the room or climbing onto the examination table.  Which of the following bursae is most likely affected in this patient?

A 36-year-old woman is evaluated for several months of tingling and numbness of the right hand and fingers that has progressed to dull, aching pain.  The symptoms initially were intermittent but have become persistent, with the pain worsening overnight.  The patient works as an office secretary and has had difficulty typing and holding the phone due to hand weakness.  On examination, she has weakness of thumb opposition and atrophy of the thenar eminence.  The patient attempted treatment with conservative measures but had no significant improvement and has now been referred for surgery.  During surgery, incision of which of the following structures is most likely to improve this patient’s symptoms?

A 45-year-old man comes to the office due to right ankle pain for the past 2 days.  The patient was running downhill on a dirt trail when he twisted his ankle inward.  Since then, he has had pain and swelling at the right ankle but is able to walk unassisted.  The patient has no other medical conditions and takes no chronic medications.  On examination, there is bluish discoloration over the lateral aspect of the joint.  He has maximal tenderness to palpation at the anterolateral aspect of the ankle joint.  Forced inversion of the foot also increases the pain.  Which of the following structures is most likely injured in this patient?

A 21-year-old man is brought to the emergency department following an assault.  He was attempting to escape and turned away just as his attacker lunged toward him from behind with a knife.  The patient suffered a 4-cm-wide penetrating injury with significant associated blood loss.  Following initial stabilization, he is transferred to the operating room.  Surgical exploration reveals injury to a muscle that assists in internal rotation of the arm and is innervated by the thoracodorsal nerve.  Which of the following muscles depicted in the cadaveric specimen is most likely injured in this patient?

A 46-year-old woman is brought by ambulance to the emergency department following a ground-level fall at home.  She slipped while getting out of the shower and hit her left knee on the tile floor.  The patient developed severe left knee pain and swelling and is unable to ambulate.  Examination shows a contusion and soft tissue swelling at the knee with a large knee effusion.  X-ray of the knee is shown in the image below:

Which of the following examination findings would most likely be seen in this patient?

A 16-year-old girl comes to the office due to several months of left elbow pain.  The pain is worse with activity and limits her exercise.  She has attempted treatment with over-the-counter ibuprofen and acetaminophen but has had only partial relief.  Medical history is notable for seasonal allergies, and current medications include a fluticasone nasal spray.  Further evaluation shows that the patient’s condition is due to a tendon injury.  A long-acting glucocorticoid injection is administered at the most tender spot, as marked in the image below.

Which of the following actions is most likely performed by the affected muscle?

 3-year-old boy is brought to the emergency department after falling off a jungle gym.  The boy tried to catch himself and landed on his outstretched arms.  He did not lose consciousness and has been crying inconsolably since he fell.  Pulse is 140/min; all other vital signs are within normal limits.  Physical examination reveals tenderness and swelling over the anterior portion of his right shoulder with crepitus over the swollen area.  An x-ray of his right shoulder is shown below.

Tension from which of the following muscles is most likely responsible for displacement of the distal bone fragment?

A 16-year-old high school quarterback comes to the office due to left shoulder pain.  One week ago, he suffered an injury during a football game.  The patient was running with the football when another player tackled him to the ground, causing him to land directly on the posterior aspect of his left shoulder.  He developed severe pain immediately and did not return to the game.  The patient has had persistent shoulder pain since the injury despite using ice and over-the-counter ibuprofen.  He has been unable to resume playing football due to pain and weakness in his shoulder.  On examination, there is diffuse bruising over the posterior aspect of the left shoulder.  Abduction of the left arm is normal, but external rotation against resistance is weak and painful.  Which of the following muscles is most likely injured?

 20-year-old college football quarterback is evaluated in the emergency department for acute right shoulder pain.  The patient sustained a blow to the arm an hour ago after he was tackled midthrow during a championship game.  On physical examination, there is flattening of the right deltoid muscle and insensitivity of the overlying skin to pinprick.  Peripheral pulses in the upper extremities are intact.  Which of the following injuries is most likely responsible for this patient’s findings?

A 34-year-old woman comes to the physician complaining of easy fatigability.  She lives alone and works as an accountant.  Her menstrual cycles are regular and her last menstrual period was 2 weeks ago.  She does not smoke or consume alcohol.  Her blood pressure is 150/90 mm Hg and pulse is 82/min.  During her physical examination, she sits up from the supine position without using her hands.  Which of the following muscles contributes most to the described movement?

A 43-year-old man comes to the office due to difficulty walking.  The patient was seen at an outpatient clinic 2 days ago and received a right-sided deep intramuscular injection.  He had no trouble walking at the time of the appointment but started having problems later that day.  The patient has no history of trauma or pain at the injection site.  Physical examination is negative for local erythema and swelling, and the patient has full strength against resistance on knee flexion and ankle plantar flexion bilaterally.  When the patient is asked to walk across the room, his left hip drops every time he raises his left foot.  Which of the following locations is the most likely site of this patient’s intramuscular injection?

A 24-year-old man is brought to the emergency department due to right arm pain after a fall.  While rock climbing at a nearby national park, the patient lost his grip and fell approximately 3 m (10 ft) onto the boulders below.  He says, “I landed on my right arm and heard something snap.”  The patient did not strike his head or lose consciousness.  He has no chronic medical conditions and takes no daily medications.  Vital signs are within normal limits.  Physical examination shows extensive bruising over the lateral right arm and a total inability to extend the right wrist.  X-ray reveals a midshaft fracture of the right humerus.  Which of the following arteries is most likely to be injured in this patient?

A 54-year-old woman comes to the emergency department due to a hand injury after a fall.  The patient slipped in the bathroom and fell backwards onto her extended right hand.  She was able to get up but has had right wrist pain and finger numbness since the fall.  Medical history is notable for obesity, hypertension, and type 2 diabetes mellitus.  On examination of her right hand, there is decreased sensation in the palmar aspect of her first three digits and a small bump is noted just below the palm.  Lunate dislocation causing median nerve compression is suspected.  Which of the following marked bones on a normal x-ray is most likely dislocated in this patient?