Osteoarthritis (OA) of the ankle is the progressive damage to the articular surface of the ankle joint including cartilage and subchondral bone which usually leads to pain joint stiffness and functional loss.
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Epidemiology
Ankle osteoarthritis is uncommon in the general population and prevalence is estimated at ~1% 1.
Risk factors
Activities with an increased risk of ankle osteoarthritis include 1:
- football (soccer)
- dancing
Other risk factors include 1:
Associations
Ankle osteoarthritis is primarily associated with previous traumatic events as well as chronic ankle instability or subtalar instability 1. The latency between a significant trauma and development of end-stage osteoarthritis is very variable with an average of about 21 years 1.
Clinical presentation
The typical complaint is pain and impaired function of the ankle joint. Pain might be described as weather dependant or occur at night, it might be closely related to sportive activities and remaining hours to days after cessation 1. Joint instability and pain-related psychological stress are additional symptoms.
Pathology
Osteoarthritis is characterized by progressive joint alteration, due to a combination of mechanical, inflammatory and metabolical factors affecting the hyaline cartilage, the subchondral bone, the joint capsule and the synovium as well as the surrounding ligaments 1.
Etiology
Unlike in knee or hip osteoarthritis, primary osteoarthritis of the ankle is rare and secondary osteoarthritis is much more common including the following causes 1:
- previous trauma, fractures or ligamentous injuries
- osteochondral lesions, osteonecrosis of the talus
- overuse
- inflammatory joint disease, e.g. rheumatoid arthritis, gout or septic arthritis
- hemochromatosis, hemophilia, neuropathic disease
- idiopathic/unknown
Radiographic features
Like in other joints osteoarthritis of the ankle is characterized by osteophyte formation joint space narrowing, subchondral sclerosis and subchondral cyst formation, remodeling of the articular surfaces or deformity in more advanced stages 3,4.
Plain radiograph
Weight-bearing AP and lateral views of the ankle and mortise views are done for the assessment of osteoarthritis. The Saltzmann view can be acquired for the evaluation of hindfoot alignment 1.
The medial, superior tibiotalar space and tibiofibular joint space are evaluated.
The Kellgren and Lawrence score has been modified for the ankle joint 4:
- grade1: osteophytes of questionable significance on the medial or lateral malleolus, rare tibial sclerosis, no joint space narrowing
- grade 2: osteophytes on the medial malleolus, no joint space narrowing
- grade 3: osteophytes on the medial and/or lateral malleolus, moderate joint space narrowing <50%
- grade 3a: talar tilt <2°
- grade 3b: talar tilt ≥2°
- grade 4: osteophytes on medial and lateral malleoli as well as tibiotalar joint margins, severe (>50%) joint space narrowing, constant tibiotalar sclerosis
It is considered reliable and has been shown to correlate with clinical symptoms 4. Kellgren and Lawrence grade ≥1 is consistent with ankle osteoarthritis.
A grading of different features of osteoarthritis can be also achieved by using the OARSI atlas 3.
MRI
In addition to osteophyte formation, joint space narrowing and subchondral sclerosis and subchondral cysts as well as kissing lesions MRI can detect joint effusion, synovitis and bone marrow edema as a possible cause of pain.
It can also detect underlying etiologies including ligament and tendon injuries osteochondral lesions as well as ankle impingement syndromes or signs of previous surgery 5.
CT/MR arthrography
CT arthrography is the imaging modality of choice in cartilage evaluation in the postoperative ankle joint to rule out early osteoarthritis.
MR arthrography can be used in situations where there are no metallic components.
Radiology report
The radiological report should include a description of the following:
- presence and the location of osteophyte formation
- joint space narrowing and joint space width
- subchondral sclerosis
- presence of subchondral cysts and/or bone erosion
- other findings e.g. subchondral fractures, signs of osteonecrosis, avulsions
The MRI report should mention the following additional feature:
- cartilage injury
- subchondral bone marrow edema
- joint effusion, synovitis
- ligament tears
Treatment and prognosis
The main objectivities in the treatment of ankle osteoarthritis are pain control and functional maintenance or restoration like in other joints. Non-operative management involves patient education, lifestyle and activity modifications including weight loss, physical therapy and pain management e.g. with acetaminophen and nonsteroidal anti-inflammatory drugs 6. Surgical management includes distraction arthroplasty, conventional arthroplasty and arthrodesis 7.
Differential diagnosis
Clinical conditions that can mimic the clinical presentation or the imaging appearance of ankle osteoarthritis include the following: