The effects of ankylosing spondylitis are cumulative as inflammation causes vertebral bone erosion, tissue scarring, and worsening symptoms. This process can eventually lead to new bone formation and spinal joint fusion.
Lower back pain that gets worse with rest and radiates down the buttock and thigh is a typical early symptom of ankylosing spondylitis.
This article provides an overview of the development and progression of ankylosing spondylitis.
How Ankylosing Spondylitis Affects Joints
Ankylosing spondylitis is a condition that affects mainly the fibrous tissue junctions where ligaments and tendons attach to bone, called entheses. Entheses are also referred to as insertion sites, osteotendinous junctions, or osteoligamentous junctions. There are two types of entheses:
- Fibrous entheses, in which the fibrous tissue of the tendon or ligament attaches to the bone.
- Fibrocartilaginous entheses, in which the connection between tendon or ligament and bone is augmented with fibrocartilage. The stiff fibrocartilage helps absorb some of the physical stress experienced at these connections.