What is the Knee Joint?

The knee joint is made up of three bones:

• Femur (thigh bone)
• Tibia (shin bone)
• Patella (kneecap)

These bones are covered with a smooth layer called articular cartilage. This cartilage helps the bones move smoothly against each other with minimal friction and decreases the amount of load the underlying bone endures.

What is a Cartilage Injury?

A cartilage injury is when there’s damage to this smooth coating layer, similar to chipped paint on your walls. This kind of injury can happen to anyone, but it’s more common in people over 40 and can also affect younger people after accidents.

Causes of Cartilage Injuries

Most cartilage injuries happen suddenly, like when you twist your knee awkwardly or fall on it. If the bone beneath the cartilage is also hurt, it’s called an osteochondral injury.

Types of Cartilage Damage

1. Focal Damage: A specific area of cartilage is damaged (like a pothole in a street).
2. Diffuse Damage: The cartilage thins out over a larger area (like a worn-out road).

Cartilage injuries are graded:

• Grade 0: Normal healthy cartilage
• Grade I: Mild damage such as softening of the cartilage
• Grade II: partial thickness injury less than 50% of the depth
• Grade III: High grade partial thickness greater than 50% of the depth
• Grade IV: Severe damage, where the cartilage is completely gone.

Symptoms of Cartilage Injuries

• Pain: Usually a dull ache that can get sharper, especially when moving.
• Stiffness: The knee may feel tight and hard to move.
• Reduced Range of Motion: It might be tough to bend or straighten the knee fully.
• Crepitus: You might hear or feel a grinding noise in the knee.
• Catching or Locking: The knee might get stuck if there’s a loose piece of cartilage.
• Swelling: The knee may fill with fluid.

How are Cartilage Injuries Diagnosed?

1. Physical Exam: The doctor will check how well you can move your knee and look for swelling or tenderness.
2. Imaging: X-rays help show cartilage damage through loss of normal joint space, while an MRI gives a clearer picture of the injury.
3. Knee Arthroscopy: This is a procedure where a tiny camera is put into the knee to see the injury directly.