A 24-year-old man comes to the urgent care clinic due to severe right knee pain. He was playing football with friends earlier that afternoon when he was tackled from the right side. He felt a pop and had difficulty walking and pivoting, but he is able to ambulate slowly. On physical examination, the patient has pain when externally rotating the right tibia with the right knee bent at a 90-degree angle. Pain and moderate laxity are demonstrated with valgus stress testing of the knee. There is no significant effusion. Plain film of the knee is normal. What is the most likely diagnosis?

Question

A 24-year-old man comes to the urgent care clinic due to severe right knee pain.  He was playing football with friends earlier that afternoon when he was tackled from the right side.  He felt a pop and had difficulty walking and pivoting, but he is able to ambulate slowly.  On physical examination, the patient has pain when externally rotating the right tibia with the right knee bent at a 90-degree angle.  Pain and moderate laxity are demonstrated with valgus stress testing of the knee.  There is no significant effusion.  Plain film of the knee is normal.  What is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c1d2_06a0_8f63_4d845a0c81f9_MD0005_00 Medial collateral ligament (MCL) tear is a common knee injury that is typically caused by a valgus (abductor) stress to the partially flexed knee. It typically occurs following a blow to the lateral knee with the foot fixed but may also be seen following a severe twisting injury (eg, skiing). MCL tears may occur in isolation or can be associated with injury to the medial meniscus. MCL tears are characterized by tenderness at the medial knee and laxity when the foot is forced into abduction with the knee stationary (valgus stress test). Acute effusion/hemarthrosis is uncommon unless there is concurrent injury to the anterior cruciate ligament. Due to local swelling and muscle spasm, examination findings may be unclear if the patient is examined more than 30 minutes after the injury; in such cases, repeat examination at a later date may reveal the full extent of the injury. X-ray is not needed unless there is concern for additional bony injury, and MRI is generally reserved for patients being considered for surgical intervention. Patients with uncomplicated MCL tears can be managed nonoperatively with rest, ice, compression, and elevation (RICE measures) and analgesics, with progressive return to activity as tolerated. (Choice A) Anterior cruciate ligament tears occur during rapid pivots, deceleration, or direction changes, or from a blow to the knee with a significant twisting force. Rapid-onset hemarthrosis is common. Examination shows laxity with the anterior drawer or Lachman maneuver. (Choice B) Lateral collateral ligament injury is associated with tenderness and pain along the lateral joint line and is most frequently caused by an injury involving dramatic varus (adductor) stress. (Choice D) Posterior cruciate ligament injury is often caused by hyperextension or by a blow to the anterior aspect of the proximal tibia with the knee flexed. It is usually associated with little pain or alteration in range of motion, but the posterior drawer test is positive. (Choice E) Prepatellar bursitis is most frequently caused by trauma from a fall or secondary to prolonged friction and pressure from repetitive kneeling ("housemaid's knee"). Educational objective: Medial collateral ligament injuries commonly occur when a force is applied to the knee from the lateral to medial direction during skiing or contact sports. Examination shows valgus laxity. Most patients are managed nonoperatively. References: Treatment of medial collateral ligament injuries. (http://www.ncbi.nlm.nih.gov/pubmed/19264708)

A 24-Year-Old Man Comes to the Urgent Care Clinic Due