What causes ankylosis of joints?

Causes of Joint Ankylosis

Joint ankylosis results from chronic inflammatory arthritis (particularly spondyloarthropathies and erosive inflammatory conditions), post-traumatic injury, septic arthritis, and severe erosive osteoarthritis, with the specific cause and location varying by disease pattern and joint involvement.

Inflammatory Arthropathies

Spondyloarthropathies

• Ankylosing spondylitis is the prototypical cause of spinal and sacroiliac joint ankylosis, characterized by progressive fusion that typically begins in the sacroiliac joints and ascends the spine 1.
• The disease is strongly associated with HLA-B27 and leads to ossification of spinal ligaments and facet joint fusion, creating the classic "bamboo spine" appearance 1.
• Peripheral joint ankylosis can occur in spondyloarthropathies, though less commonly than axial involvement 1.

Rheumatoid Arthritis

• Wrist ankylosis develops in approximately 10.6% of RA patients on MRI, significantly higher than the 0.8% detected on conventional radiographs 2.
• Ankylosis in RA is associated with longer disease duration and severe disease, typically occurring after years of chronic inflammation 2.
• Proximal interphalangeal (PIP) joint ankylosis can occur as autofusion, representing an endpoint of severe joint destruction 3.
• The wrist typically shows progressive joint space narrowing in a pericapitate or carpometacarpal distribution, with ankylosis developing after 1.5–3 years of disease onset 1.

Adult-Onset Still's Disease (AOSD)

• Pericapitate ankylosis develops in 25% of AOSD patients with the characteristic pattern of intercarpal and carpometacarpal joint space narrowing 1.
• AOSD also causes ankylosis of distal interphalangeal joints, intertarsal joints, and cervical zygapophyseal joints 1.
• The chronic articular form of AOSD carries particularly high risk for progressive ankylosis 1.

Erosive Osteoarthritis

• Erosive hand osteoarthritis targets interphalangeal joints and can progress to marked bone attrition, instability, and bony ankylosis 1.
• This subset shows subchondral erosion that may advance to complete fusion, typically with more severe pain and functional impairment than non-erosive osteoarthritis 1.
• Ankylosis in erosive OA is specific to this subtype and distinguishes it from nodal osteoarthritis 1.

Infectious Causes

Septic Arthritis

• Neonatal septic arthritis, particularly of the temporomandibular joint, can result in complete ankylosis if undiagnosed or inadequately treated 4, 5.
• Common causative organisms include Staphylococcus aureus, Neisseria gonorrhoeae, and Haemophilus influenzae 4.
• When occurring during early childhood, septic arthritis leads to severe functional disability and facial deformity in TMJ cases 4, 5.

Post-Traumatic Ankylosis

• Direct joint injury or indirect trauma consequences can cause partial or total hip joint ankylosis, representing a severe and permanent handicap 6.
• Post-traumatic ankylosis results from altered joint mechanics, prolonged immobilization, intra-articular fractures, or heterotopic ossification 6.
• The pathogenesis does not fundamentally differ from other etiologies, making prevention through early mobilization and appropriate fracture management critical 6.

Clinical Pitfalls and Considerations

Key diagnostic distinctions:

• Psoriatic arthritis may target distal interphalangeal joints or affect single rays, mimicking erosive osteoarthritis 1.
• Hemochromatosis primarily targets metacarpophalangeal joints and wrists, a different pattern than typical osteoarthritis 1.
• Gout may superimpose on pre-existing osteoarthritis, complicating the clinical picture 1.

Imaging considerations:

• Plain radiographs remain the gold standard for detecting established ankylosis, showing complete joint space obliteration and bony bridging 1.
• MRI is superior for detecting early ankylosis, particularly in the wrist, identifying cases missed on conventional radiography 2.
• In ankylosing spondylitis, patients with spinal ankylosis have high risk of unstable fractures from minor trauma, requiring high clinical suspicion and CT imaging when symptomatic 1.