Cartilage itself doesn't have nerves, so pain arises indirectly when cartilage is damaged.
How Cartilage Damage Causes Pain
When cartilage, the smooth tissue covering the ends of bones in a joint, is damaged or worn away, it can lead to pain through a few key mechanisms:
- Bone Exposure: When cartilage wears away, it can expose the underlying bone. Unlike cartilage, bone does have nerve endings. This exposed bone becomes sensitive and can generate pain signals.
- Joint Lining Irritation (Synovitis): Cartilage damage can irritate the synovium, the membrane lining the joint. This irritation causes inflammation, called synovitis, which is a common source of pain in joint conditions. The inflamed synovium releases chemicals that stimulate pain receptors.
- Bone on Bone Contact: As cartilage deteriorates, bones within the joint can begin to rub directly against each other. This friction causes pain, inflammation, and further damage.
- Loose Cartilage Fragments: Damaged cartilage can break off into small fragments within the joint. These fragments can irritate the synovium and cause pain, clicking, or catching sensations within the joint.
Examples of Conditions Where Cartilage Damage Causes Pain
Common conditions where cartilage damage leads to pain include:
- Osteoarthritis: This is a degenerative joint disease where cartilage gradually wears away over time.
- Chondral Defects: These are localized areas of cartilage damage, often resulting from injury.
- Meniscus Tears: While the meniscus is technically fibrocartilage, tears can lead to instability and abnormal joint mechanics, accelerating cartilage wear and subsequent pain.
In summary, while cartilage itself lacks nerves, its damage triggers pain by exposing bone, irritating the joint lining, causing bone-on-bone contact, and creating loose cartilage fragments.
