Cartilage
A firm but flexible connective tissue that cushions joints, forms structural frameworks (ears, nose, trachea), and provides smooth surfaces for bone movement. Articular cartilage in joints has limited capacity to heal once damaged, making its preservation a central goal in orthopedic longevity.
Cartilage is a specialized connective tissue composed of chondrocytes (cartilage cells) embedded in an extracellular matrix of collagen fibers, proteoglycans, and water. It is avascular — it has no blood supply — which gives it both its unique mechanical properties and its limited capacity for repair.
Types of Cartilage
Hyaline Cartilage
The most common type. Forms the smooth, glassy articular surfaces of joints (articular cartilage), the tracheal rings, and the growth plates (physes) in developing bones. Hyaline cartilage provides low-friction surfaces for joint movement and distributes mechanical loads across the joint.
Fibrocartilage
Contains more collagen fibers and is tougher than hyaline cartilage. Found in the menisci of the stifle (knee), intervertebral discs, and the pubic symphysis. Fibrocartilage handles compression and tensile forces simultaneously.
Elastic Cartilage
Contains elastic fibers in addition to collagen, making it more flexible. Found in the ear pinnae and epiglottis. Less clinically significant in orthopedic disease but important for structural function.
Articular Cartilage and Joint Health
Articular cartilage is 2-5mm thick in canine joints and serves as the bearing surface that allows near-frictionless movement. Its composition is approximately 65-80% water, 10-20% collagen (primarily type II), and 5-10% proteoglycans (primarily aggrecan). This structure creates a hydrated, compressible surface that absorbs impact and distributes load.
The critical limitation of articular cartilage is its inability to heal effectively. Because it lacks blood vessels, nerves, and lymphatics, the repair mechanisms available to other tissues are absent. Damage to articular cartilage — from trauma, developmental abnormalities (hip dysplasia, elbow dysplasia, OCD), or chronic overload — tends to be permanent and progressive.
Why Cartilage Loss Matters for Longevity
Cartilage degeneration leads to osteoarthritis, the most common cause of chronic pain and mobility loss in aging dogs. Once the cartilage surface is lost, bone-on-bone contact produces pain, inflammation, and progressive joint deterioration. This is why cartilage-protective strategies — weight management, controlled exercise, joint supplementation with glucosamine and chondroitin, and early intervention for developmental joint disease — are central to orthopedic longevity planning.
Cartilage Support Strategies
- Maintain lean body weight to reduce joint loading
- Avoid repetitive high-impact activity during skeletal growth
- Provide controlled, low-impact exercise (swimming, leash walks) throughout life
- Consider joint supplements with potential chondroprotective effects
- Address developmental joint abnormalities early, before secondary cartilage damage progresses