A 25-year-old man comes to the physician because of left knee pain for 2 weeks. The pain started while playing basketball after suddenly hearing a popping sound. He has been unable to run since this incident. The patient appears healthy and well-nourished. His temperature is 37°C, pulse is 67/min, and blood pressure is 120/80 mm Hg. Examination of the left knee shows medial joint line tenderness. Total knee extension is not possible and a clicking sound is heard when the knee is extended. An x-ray of the left knee shows no abnormalities. Which of the following is the most appropriate next step in management?

A 36-year-old woman comes to the physician because of new onset limping. For the past 2 weeks, she has had a tendency to trip over her left foot unless she lifts her left leg higher while walking. She has not had any trauma to the leg. She works as a flight attendant and wears compression stockings to work. Her vital signs are within normal limits. Physical examination shows weakness of left foot dorsiflexion against minimal resistance. There is reduced sensation to light touch over the dorsum of the left foot, including the web space between the 1st and 2nd digit. Further evaluation is most likely to show which of the following?

A 27-year-old man is brought to the emergency department because of left shoulder pain and inability to move the shoulder for the past 45 minutes. The patient noticed these symptoms after he had a generalized tonic-clonic convulsion. His last seizure was 4 months ago. Examination shows that the left arm is adducted and internally rotated. The anterior left shoulder is flattened with prominence of the coracoid process. The right upper extremity shows no abnormalities. Sensation over the lateral surface of both shoulders is normal. Radial pulses are palpable bilaterally. Oropharyngeal examination shows a tongue laceration. Which of the following is the most appropriate next step in the management of this patient?

A 25-year-old woman is brought to the emergency department after being involved in a rear-end collision, in which she was the restrained driver of the back car. On arrival, she is alert and active. She reports pain in both knees and severe pain over the right groin. Temperature is 37°C (98.6°F), pulse is 116/min, respirations are 19/min, and blood pressure is 132/79 mm Hg. Physical examination shows tenderness over both knee caps. The right groin is tender to palpation. The right leg is slightly shortened, flexed, adducted, and internally rotated. The remainder of the examination shows no abnormalities. Which of the following is the most likely diagnosis?

An inconsolable 18-month-old girl is brought to the emergency department after falling from a bed. Vital signs are within normal limits. Examination of the right forearm reveals a mild swelling distally with an angulation deformity. Her radial arm pulses are strong and symmetric. A lateral x-ray of the right wrist shows a greenstick fracture with severe angulation deformity. An anteroposterior radiograph reveals a discontinuity of the cortex on the lateral side of the distal radius with a 20° medial angulation deformity. Which of the following is the most appropriate next step in management?

A 12-year-old boy is brought to the physician because of a 6-day history of gradually worsening left knee pain. The pain is exacerbated by movement and kneeling. There is no pain at rest and no history of trauma to the knee. He is concerned because his soccer tryouts are in a few days. Vital signs are within normal limits. Examination shows mild swelling and tenderness to palpation of the left anterior, superior tibia. Extension of the left knee against resistance reproduces the knee pain; flexion is limited by pain. There is no local erythema or effusion of the left knee. A lateral view of an x-ray of his left knee is shown. Which of the following is the most likely underlying cause of this patient's symptoms?

A 56-year-old man comes to the physician because of lower back pain for the past 2 weeks. The pain is stabbing and shooting in quality and radiates down the backs of his legs. It began when he was lifting a bag of cement at work. The pain has been getting worse, and he has started to notice occasional numbness and clumsiness while walking.Peripheral pulses are palpable in all four extremities. Neurological examination shows 5/5 strength in the upper extremities and 3/5 strength in bilateral foot dorsiflexion. Sensation to light touch is diminished bilaterally over the lateral thigh area and the inner side of lower legs. Passive raising of either the right or left leg causes pain radiating down the ipsilateral leg. Which of the following is the most appropriate next step in management?

A 64-year-old man with osteoarthritis of the knee comes to the physician for evaluation of weakness in his foot. Physical examination shows a swelling in the popliteal fossa. There is marked weakness when attempting to invert his right foot. He is unable to curl his toes. Further evaluation of this patient is most likely to show decreased sensation over which of the following locations?

A previously healthy 13-year-old boy is brought to the physician because of a 4-week history of dull pain in the left hip. He is able to bear weight on the left hip but has severe pain when walking that has progressively worsened for the past 2 days. The pain does not radiate. His temperature is 37.1°C (98.9°F). Physical examination shows restricted internal rotation and abduction of the left hip; the left groin is tender to palpation. When walking, he stands on his right leg for longer than his left leg, and he swings his left leg longer than his right leg. His leukocyte count is 7000/mm3 and erythrocyte sedimentation rate is 13 mm/h. Which of the following is the most likely underlying cause of this patient's condition?

A 23-year-old man is brought to the emergency department because of severe right shoulder pain and inability to move the shoulder for the past 30 minutes. The pain began after being tackled while playing football. He has nausea but has not vomited. He is in no apparent distress. Examination shows the right upper extremity externally rotated and slightly abducted. Palpation of the right shoulder joint shows tenderness and an empty glenoid fossa. The right humeral head is palpated below the coracoid process. The left upper extremity is unremarkable. The radial pulses are palpable bilaterally. Which of the following is the most appropriate next step in management?

A 13-year-old boy is brought to the physician because of growing pains. One week before the pain started, the patient was hit in the thigh by a baseball, which caused his leg to become red and swollen for several days. Vital signs are within normal limits. Examination shows marked tenderness along the left mid-femur. His gait is normal. Laboratory studies show a leukocyte count of 21,000/mm3 and an ESR of 68 mm/h. An x-ray of the left lower extremity shows multiple lytic lesions in the middle third of the femur, and the surrounding cortex is covered by several layers of new bone. A biopsy of the left femur shows small round blue cells. Which of the following is the most likely diagnosis?