Meniscus tear

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Meniscus tear

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USMLE® Step 1 style questions USMLE

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USMLE® Step 2 style questions USMLE

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A 21-year-old man presents to the clinic to be evaluated for right knee pain. The patient was playing basketball three weeks ago when he suddenly pivoted while running and dribbling to the basket and felt pain in the right knee. Since then, he has experienced pain that worsens with running. In addition, he feels like his knee is “catching” and “giving out”. He is otherwise healthy and does not take any medications. Vital signs are within normal limits. Physical examination of the bilateral knees does not demonstrate effusions or deformities When the examiner grasps the patient's thigh and pulls the tibia forward with the knee at 20° of flexion, there is no anterior translation of the tibia or “soft” end-feel. When the examiner attempts to translate the lower leg posteriorly, there is no “soft” end-feel or excessive posterior translation.. There is tenderness to palpation over the medial right joint line. No pain is elicited when the examiner flexes the right knee to maximal flexion beyond 90° and then extends the knee with internal rotation of the tibia and a varus stress. When the examiner returns the knee to maximal flexion and extends the knee with external rotation of the tibia and a valgus stress  pain and clicking are noted. Radiograph of the knee shows no fracture. Which of the following is the most likely diagnosis?  

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The menisci are crescent-shaped fibrocartilage cushions found in the knee joint.

Normally, there’s the medial and lateral menisci between the femur and the tibia.

So, a meniscus tear, more commonly known as torn knee cartilage, is when one of the menisci of the knee is torn.

This usually occurs due to trauma during contact sports.

The knee is a complex joint, actually it’s a combination of three joints.

These are the femoropatellar joint, between the femur and patella, and the two tibiofemoral joints which are formed by the bony prominences, also called the condyles of the tibia and the femur.

Between the femoral and tibial condyles, there’re the medial and lateral menisci.

The menisci act to absorb compressive force, which can reach up to three times the body weight while walking!

In addition, the menisci have a cup-shaped surface which provides a deeper place for the condyles to fit in improving joint’s stability.

Next, the knee joint is supported by a number of ligaments.

So, within the joint space, there's the anterior cruciate ligament, or ACL, which runs from the anterior middle edge of the tibia to the lateral condyle of the femur, and the posterior cruciate ligament, or PCL, that runs from the middle posterior edge of the tibia to the medial condyle of the femur.

Now, outside the joint space, we’ve got one collateral ligament between the femur and the tibia on each side of the joint, which are the lateral collateral ligament, or LCL, and the medial collateral ligament, or MCL.

The MCL is firmly attached to the medial meniscus, which makes it less mobile compared to the lateral meniscus.

A meniscus tear can occur when the meniscus is violently compressed, called an acute tear, which usually occurs in young athletes.

Acute tears typically occur when the knee is bent and at the same time excessively twisted, like when you’re playing basketball and then you suddenly change direction, trying to crossover another player.

Acute meniscus tears can also occur as a part of the unhappy triad injury.

Summary

Meniscus tear is when one or both of the menisci of the knee joint are torn. Acute tears usually occur in athletes during contact sports, when the menisci are violently compressed. Chronic tears can also occur, often in older people due to wear and tear changes of menisci. Symptoms include pain, swelling, and stiffness, and the diagnosis is mainly based on clinical symptoms, physical exam with an MRI for confirmation. Treatment can be conservative, or by open or arthroscopic surgery.

Sources

  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine" McGraw Hill Education/ Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Meniscal Injuries in the Young, Athletically Active Patient" The Physician and Sportsmedicine (2011)
  6. "Risk Factors for Meniscal Tears: A Systematic Review Including Meta-analysis" Journal of Orthopaedic & Sports Physical Therapy (2013)
  7. "The menisci: basic science and advances in treatment" British Journal of Sports Medicine (2000)
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