Causes / typical injury mechanism: Arthritis of the ankle typically results from previous traumatic injury, but it can also be caused by primary osteoarthritis or secondary degenerative conditions. Secondary degenerative causes are less common and include rheumatoid arthritis and hemochromatosis.

Septic arthritis of the ankle is rare and distinguishable from other forms of ankle arthritis due to its acute onset and association with fever.

Classic history and presentation: A typical presentation for ankle arthritis will be a patient in their 50s presenting with gradually, progressively worsening ankle pain that is worse with activity. Medical history will usually involve previous traumatic injury to the ankle (fracture or ligamentous damage). The patient may also present with reduced range of motion or visible deformity.

Prevalence:

• Most commonly occurs in adults in their 50s for posttraumatic arthritis and adults in their 60s for primary degenerative osteoarthritis, with roughly equal prevalence between sexes.
• One percent of adults have some degree of arthritis of the ankle.

Risk factors:

• Previous ankle trauma
• History of rheumatoid arthritis or a family history of arthritis

Pathophysiology:

• The pathophysiology of primary degenerative ankle arthritis involves the progressive degeneration of articular cartilage. Aging, mechanical stress, and potential underlying inflammatory conditions all likely play roles in this degeneration.
• The pathophysiology of traumatic ankle arthritis typically involves joint degeneration and injury from fractures of the malleolus, tibial shaft, or tibial plafond. Previous fracture of the malleolus is the most common, seen in around 40% of ankle arthritis patients.
• In both primary degenerative osteoarthritis and posttraumatic arthritis, degeneration of cartilage leads to bone-bone contact, osteophyte formation, and other anatomical deformities, causing pain and reduced range of motion.

Grade / classification system: Ankle arthritis can be classified by the van Dijk system based on radiographic evaluation of the ankle joint. Other systems, such as the Takakura and Kellgren systems, can also be used; however, the van Dijk system has been found to have slightly better reliability.

van Dijk classification system –

• Grade 0: normal joint or subchondral sclerosis
• Grade I: osteophytes without joint space narrowing
• Grade II: joint space narrowing with or without osteophytes
• Grade III: (sub)total disappearance or deformation of the joint space