Articular cartilage

What it is

Articular cartilage, also called hyaline cartilage, is made of water, collagen fibres and molecules that hold that water like a sponge. When you load the knee, fluid moves within it, cushioning the bone beneath. It has no blood vessels and no nerves, and gets its nutrition from the joint fluid as you move.

It is different from the menisci, which are separate C-shaped pads of tougher fibrocartilage. People often use the word cartilage for both.

Why it matters for patients

Because it lacks a blood supply, articular cartilage heals poorly. Damage can come from a single injury, such as a twist or a kneecap dislocation that knocks off a piece, or from gradual wear, which is the core of knee osteoarthritis. Cartilage itself does not hurt, so pain comes from the bone beneath, the inflamed lining and swelling.

Symptoms of a cartilage problem include aching with activity, swelling afterwards, grinding, and catching if a loose piece is present.

How it is examined and treated

Standing X-rays show cartilage loss indirectly as joint-space narrowing. MRI shows defects directly. Treatment depends on the size of the defect and your age and goals, ranging from weight management, strengthening and injections to arthroscopic procedures, cartilage restoration in suitable younger patients, and joint replacement for advanced arthritis.