This page provides a summary of the key findings of the IFOAC paper International Foot and Ankle Osteoarthritis Consortium review and research agenda for diagnosis, epidemiology, burden, outcome assessment and treatment.

If you are interested in increasing your knowledge of OA, we also recommended ATLAS (Arthritis Training, Learning and Upskilling), which is a free resource developed by the Australian Government. Click here for details.

Diagnosis and clinical assessment of foot OA

Imaging diagnosis

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Traditionally, the diagnosis of OA through radiographic methods has relied on the Kellgren and Lawrence (KL) system. However, it's important to note that this system was initially developed for knee OA and may not be entirely suitable for diagnosing OA in the foot and ankle. In response to this limitation, the La Trobe Foot Atlas was created to facilitate the radiographic diagnosis of OA in specific foot and ankle joints, including the first metatarsophalangeal (MTP) joint, first cuneiform-metatarsal joint, second cuneiform-metatarsal joint, talonavicular joint, and navicular-first cuneiform joint. This atlas employs both dorsoplantar and lateral radiographic projections, separately grading the presence of osteophytes and joint space narrowing (JSN) on a scale from 0 (absent) to 3 (severe osteophyte or joint fusion). Radiographic OA (rOA) is defined as a score of ≥2 for osteophytes or JSN on either dorsoplantar or lateral views. The overall score has shown moderate-to-excellent reliability for both intra- and inter-rater assessments.

More recently, the La Trobe Foot Atlas has been expanded to include ankle joint images, and a separate atlas has been created specifically for rOA of the ankle and rearfoot. Like the original atlas, the ankle/rearfoot atlas assesses osteophytes and JSN using mortise and lateral projections for the tibiotalar, talofibular, and subtalar joints. The authors of this atlas have also proposed a modified KL grading system for all three joints, resulting in an overall score ranging from 0 (no OA) to 4 (definite osteophyte with severe JSN). Intra-rater reliability for most features on the ankle/rearfoot atlas has been found to be good-to-excellent, although inter-rater reliability varies from fair to excellent.

Magnetic resonance imaging (MRI) scoring systems are also being developed to assess the various tissues within the entire joint complex of the foot and ankle. For instance, a semiquantitative MRI scoring system for the first MTP joint has shown excellent intra-rater and inter-rater reproducibility. A similar scoring system has been developed for subtalar and talonavicular joints, demonstrating excellent overall intra-rater and inter-rater correlation. Preliminary examinations of the hindfoot, midfoot, and MTP joints using MRI have revealed good intra-rater reliability and fair inter-rater reliability when features across subregions are collectively scored. An MRI scoring system for ankle OA has exhibited 'substantial' to 'almost perfect' intra-rater and inter-rater reproducibility.

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Additionally, other imaging modalities, such as ultrasound and weight-bearing computerized tomography (CT), may offer supplementary benefits. Ultrasound has proven to be a reliable tool for evaluating synovial hypertrophy, joint effusion, and power Doppler signal, but further research is necessary to determine its potential for assessing cartilage damage and osteophytes. A formal CT scoring system for foot and ankle OA has yet to be developed.

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Clinical diagnosis

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Clinical definitions for OA in joints such as the knee, hip, and hand have been established for many years. However, there is currently no widely accepted clinical definition for foot and ankle OA. In research settings, symptomatic radiographic foot OA (srOA) is often defined by the presence of both observed radiographic OA and pain in the corresponding area. Whether a stand-alone clinical definition for foot and ankle OA is necessary or even possible is a subject of debate, but having an agreed-upon definition could potentially reduce the reliance on imaging for diagnosis. The need for separate clinical definitions for different regions of the foot and ankle also remains uncertain.

In the case of the foot, there is a shortage of evidence-based clinical diagnostic criteria. One previous study developed a clinical diagnostic rule for identifying radiographic OA in the first metatarsophalangeal (MTP) joint. This rule included factors such as the presence of longstanding pain, a palpable dorsal joint osteophyte, crepitus, hard end-feel, and restricted range of motion, and it exhibited good diagnostic accuracy, with excellent sensitivity and specificity for predicting radiographic OA at the joint.

However, diagnosing midfoot OA is more challenging due to the proximity of the midfoot joints, making it difficult to isolate and assess for tenderness, stiffness, and deformity. Clinical assessments involving measures of foot posture, range of motion, and palpable dorsal osteophytes have been shown to perform poorly in identifying radiographic OA in people with midfoot pain. Diagnosis of midfoot OA often relies on palpation of the suspected joint, sometimes with provocation tests, in conjunction with diagnostic imaging, typically plain radiographs. While local anesthetic injections can help determine which joints are symptomatic, their utility is questionable due to the small joint spaces and the potential for leakage into adjacent joints. Specific and validated clinical tests for assessing the presence of OA in the midfoot joints are lacking, with the diagnostic performance of tests like the 'piano key' test remaining undetermined.

Ankle OA, too, lacks a clinical definition. Clinicians often rely on a combination of clinical signs and symptoms such as pain, stiffness, and palpable tenderness, sometimes with imaging, to make a diagnosis. Ankle OA is frequently linked to post-traumatic factors, and there have been suggestions to consider post-traumatic ankle OA as a distinct entity, possibly necessitating a separate clinical definition.