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?

Question

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?

Quizplus · Accepted Answer

11ec160b_35e7_d658_9249_916ac62786fd_MD0001_00 This patient has a comminuted patella fracture. The patella is a large sesamoid bone that facilitates knee extension, protects the joint from direct injury, and improves nourishment of the distal femur articular cartilage. The quadriceps tendon inserts at the superior pole of the patella and wraps distally around the patella to become the patellar tendon, which inserts at the tibial tuberosity. Patella fractures are most commonly due to a direct blow to the anterior aspect of the knee (eg, landing on a flexed knee in a fall, striking the knee against the dashboard in a frontal motor vehicle collision). The patella can also be fractured indirectly due to excessive force transmitted through the quadriceps tendon (eg, landing on the feet after falling from a height). Patients develop acute swelling (often with an associated effusion), focal tenderness, inability to extend the knee against gravity, and a palpable gap in the extensor mechanism. (Choice A) The posterior cruciate ligament (PCL) protects against excessive posterior knee movement and is the least frequently injured knee ligament. PCL injury results in a positive posterior drawer test (increased backward movement of the tibia against a fixed femur). (Choice B) The medial collateral ligament (MCL) protects against valgus stress on the knee and excessive external tibial rotation. MCL injury occurs after a lateral blow to the knee or indirect stress from excessive lower leg rotation or abduction. Patients have excessive joint widening on valgus stress (eg, the femur is held in a fixed position while an abducting [lateral] force is applied to the lower leg/foot). (Choice C) The anterior cruciate ligament (ACL) controls anterior knee movement and prevents excessive tibial rotation. ACL injury often occurs due to sudden acceleration or deceleration in noncontact athletic injuries. Patients have laxity of forward movement of the tibia against a fixed femur (anterior drawer test). (Choice E) Knee flexors include the hamstring muscles (biceps femoris, semitendinosus, semimembranosus), gracilis, gastrocnemius, and sartorius. Hamstring injury can decrease hip extension and knee flexion. However, these muscles do not involve the patella. Educational objective: Patella fractures are most commonly due to a direct impact to the anterior aspect of the knee. Signs include an acutely swollen knee, focal patella tenderness, inability to extend the knee against gravity, and a palpable gap in the extensor mechanism. __________ References: Patellar fractures in adults. (http://www.ncbi.nlm.nih.gov/pubmed/21464213)

A 46-Year-Old Woman Is Brought by Ambulance to the Emergency