A synovial joint is built for smooth, low-friction movement under load. Each part has a job, and each can be a source of pain and swelling.
Articular cartilage
Smooth hyaline cartilage covers the bone ends so they glide. It has no blood supply or nerves, so it heals poorly once damaged.
Capsule and synovial membrane
A fibrous capsule encloses the joint and is lined by the synovial membrane. The membrane makes synovial fluid, a thin, slippery liquid that lubricates and nourishes the cartilage.
Ligaments
Ligaments are bands of tough tissue that connect bone to bone and block movement in the wrong direction. Tendons, which attach muscle to bone, also cross the joint and help hold it steady.
Bursae and menisci
Bursae are small fluid sacs that cushion tendons where they rub over bone. Some joints, like the knee, also have fibrocartilage pads (menisci) that deepen the socket and spread the load.
| Part | Made of | Job |
|---|---|---|
| Articular cartilage | Hyaline cartilage | Smooth gliding surface |
| Synovial membrane | Thin lining tissue | Makes synovial fluid |
| Ligament | Dense connective tissue | Connects bone to bone |
| Bursa | Fluid-filled sac | Reduces friction |
At the bedside
Fluid inside the capsule (an effusion) swells the whole joint, while bursitis swells a small area over a bony point. A hot, red, swollen joint needs its fluid tested to rule out infection or crystals.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).