What is the main difference between a cartilage injury and a ligament injury in the knee?

The knee consists of several essential structures, including bones, cartilage, and ligaments, in addition to fluids, muscles, and tendons that aid its movement. When any of these components are injured or diseased, knee problems can arise, causing pain and difficulty walking [1]. Although cartilage and ligament injuries occur in the same joint, there are fundamental differences between them regarding their function, the nature of the injury, and treatment methods.

The function of cartilage and ligaments in the knee

Cartilage is a flexible tissue that covers the ends of bones within the joint, acting as a cushion to absorb shock and facilitate smooth joint movement [1]. Ligaments are strong bands of connective tissue that connect bones to one another, providing stability to the joint and preventing excessive or abnormal movement. For example, the anterior cruciate ligament (ACL) connects the shinbone (tibia) to the thighbone (femur) [2].

The nature of the injuries

The nature of cartilage injuries differs from ligament injuries:

• Cartilage injuries: These often occur as a result of gradual cartilage wear, a common condition known as osteoarthritis (degeneration). Cartilage can wear away over time, causing pain and swelling [1]. Acute cartilage injuries, such as a meniscus tear, may also occur due to a sudden twisting movement or direct trauma.
• Ligament injuries: These usually occur as a result of a sudden movement or a severe sprain that exceeds the ligament's ability to stretch, leading to a partial or complete tear [1]. An anterior cruciate ligament (ACL) injury is very common in sports activities that involve sudden twisting movements [1]. A ligament injury may cause a feeling of knee instability or the knee giving way during physical activities [2].

Symptoms and treatment

Although both injuries can cause pain and difficulty walking, some symptoms may be more prominent in one than the other. Ligament injuries, especially to the ACL, often cause a sensation of knee instability or the knee "giving way," which may be followed by swelling and sharp pain [2]. Conversely, symptoms of cartilage wear (osteoarthritis) may develop gradually and include pain, swelling, and joint stiffness [1].

Treatment for knee problems depends on the underlying cause [1]. In cases of severe ligament injuries, such as an ACL tear, a doctor may recommend surgical ligament reconstruction to ensure knee stability and prevent a subsequent meniscus tear [2]. This surgery involves replacing the torn ligament with tissue from the patient's own body or from a donor [2]. As for cartilage injuries, treatments can range from physical therapy and lifestyle changes to surgical interventions in some cases.

When should you see a doctor?

You should consult a doctor regarding knee pain if you suffer from severe pain, noticeable swelling, an inability to bear weight on the knee, or if you feel that your knee is unstable or that it "gives way" [1]. Early diagnosis helps determine the nature of the injury and establish an appropriate treatment plan. Examinations may include magnetic resonance imaging (MRI) or X-rays [1].

For more information on common knee injuries, you can visit Common Knee Injuries: The Difference Between Cartilage, Ligaments, and Osteoarthritis (Arabic).

Medical references

• Knee Injuries and Disorders
• ACL reconstruction