Subchondral Bone
The layer of bone located directly beneath the cartilage in joints. Changes to subchondral bone, including sclerosis and cyst formation, are hallmarks of osteoarthritis progression.
Extended Definition
Subchondral bone is the specialized bone tissue that lies immediately beneath articular cartilage in synovial joints. It serves as a critical interface between the cartilage and the deeper cancellous (spongy) bone.
Structure and Function
- Shock absorption - Works with cartilage to distribute mechanical loads
- Nutrient supply - Provides nutrients to the deep layers of cartilage
- Structural support - Maintains the shape and stability of the joint surface
Changes in Osteoarthritis
As OA progresses, subchondral bone undergoes characteristic changes visible on X-rays and MRI:
- Sclerosis - Bone becomes denser and harder
- Cyst formation - Fluid-filled cavities develop
- Bone marrow lesions - Areas of abnormal signal on MRI associated with pain
- Bone remodeling - Shape changes that alter joint mechanics
These changes are why “bone-on-bone” arthritis is so painful—the protective cartilage is gone, and the underlying bone is damaged.
Related Terms
More Anatomy Terms
View allAcetabulum
The cup-shaped socket of the pelvis that holds the head of the femur (thigh bone) in the hip joint.
Articular Cartilage
The smooth, white tissue covering the ends of bones in joints. Its breakdown is the primary feature of osteoarthritis.
Bursae
Small, fluid-filled sacs that act as cushions between bones, tendons, and muscles near joints, reducing friction during movement. Singular form is 'bursa.'
Bursa
Small, fluid-filled sacs that cushion bones, tendons, and muscles near joints. Bursitis (inflammation of a bursa) can cause joint pain similar to arthritis.
Cartilage
A smooth, rubbery connective tissue that covers and protects the ends of bones where they meet to form joints, allowing them to glide smoothly during movement.