A 57-year-old man presented with a painful soft-tissue swelling at the right ankle for several months. There was no history of acute trauma or previous malignancy.
Magnetic resonance imaging (MRI), including post-gadolinium images, and ultrasound were performed.
MRI demonstrates a soft tissue mass at the posterior talocrural joint capsule. The lesion is slightly heterogeneous and is of low signal intensity on T1-weighted images (Fig. 1) and intermediate signal intensity on fat-suppressed T2-weighted images (Fig. 2). Gradient echo sequences show no blooming artefacts (Fig. 3). After IV administration of gadolinium contrast, there is marked enhancement of the lesion (Fig. 4). Note also a talocrural joint effusion and subtle bone erosion and bone marrow oedema at the talus and fibula.
Ultrasound confirms the presence of a soft tissue mass with increased power Doppler at the periphery (Fig. 5).
Additional blood testing shows a serum urate level of 9.1 mg/dL, which is above the upper reference limit of 6.0 mg/dL [1].
Gout is a common arthritis caused by deposition of monosodium urate (MSU) crystals within joints following chronic hyperuricaemia. It affects 1-2% of adults in developed countries and predominantly affects middle-aged and elderly men [2].
Acute gouty arthritis initially involves one single joint in the lower limbs, usually the first metatarsophalangeal joint. The affected joint is erythematous, warm, swollen, and tender. Untreated gout mostly resolves within a few days. Subsequent attacks frequently last longer, affect multiple joints, and spread to the upper limbs, especially the elbows and hands [2].
When left untreated, acute attacks of gout can lead to chronic gout, which is characterized by chronic destructive asymmetric polyarticular involvement with low-grade joint inflammation and tophus formation. A tophus consists of a soft tissue mass composed of MSU crystals surrounded by chronic mononuclear and giant-cell reactions. It may cause bone erosion and tissue remodelling. Tophi are frequently seen around the ear, olecranon, Achilles tendons, toes, fingers and knees [2].
Until recently, the definite diagnosis of gout required demonstration of MSU crystals in synovial fluid or tophus aspirates. However, the new 2015 gout classification criteria from the American College of Rheumatology and the European League Against Rheumatism state that, when the examination of synovial fluid or tissue samples is not feasible, a diagnosis of gout can be supported by a combination of clinical, laboratory and imaging findings. Laboratory findings include a serum urate level > 6.0 mg/dL. Imaging findings include well-defined cortical erosions with sclerotic margins and overhanging edges on conventional radiography, and/or the presence of MSU crystal deposition on ultrasound or dual-energy computed tomography [1].
Magnetic resonance imaging (MRI) is usually not needed to diagnose gout and is usually nonspecific. MRI is not able to directly demonstrate MSU crystals. Tophi are observed on MRI as amorphous and sometimes nodular regions of low-intensity signal on T1-weighted images, variable intensity on T2-weighted images and variable, patchy enhancement after intravenous contrast [3].
In our patient, concomitant cortical erosions and tophus formation at the first metatarsophalangeal joint (Fig. 6) and the history of alcohol abuse were further indicators of gout.
The main differential diagnosis is pigmented focal villonodular synovitis (PVNS). However, the age of the patient and absence of blooming artefacts on gradient echo sequences make a diagnosis of PVNS less likely [4]. Another differential diagnosis is synovial chondromatosis, which generates typical chondroid signal characteristics on MRI including high signal intensity on T2-weighted images [5].
Tophaceous gout of the posterior talocrural joint
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1. There is soft tissue swelling around the right ankle joint. MRI images show abnormal signals in the local soft tissue.
2. The lesion presents as a soft tissue nodule exhibiting relatively low signal intensity on T1-weighted images and heterogeneous signal on T2-weighted images (possibly low or mixed signal), with irregular enhancement following contrast administration.
3. Focal cortical bone erosion is observed adjacent to the joint surface, accompanied by sclerotic margins and an “overhanging rim” sign, indicating a chronic erosive process.
4. Similar changes around the first metatarsophalangeal joint and the ankle suggest previous or concurrent lesions (as shown).
5. Given the patient’s medical history, the morphology of local soft tissue masses and bone erosion is consistent with gouty tophus formation.
Considering the patient’s history, the imaging findings (signal characteristics of the soft tissue nodules, features of bone erosion), along with elevated serum uric acid and alcohol abuse history, the most likely diagnosis is Gouty Arthritis (with gouty tophus formation).
If further confirmation is needed, joint aspiration for synovial fluid analysis or puncture/biopsy of the gouty tophus can be performed to detect urate crystals.
1. Pharmacological Therapy
・During acute attacks, non-steroidal anti-inflammatory drugs (NSAIDs) or colchicine may be used to relieve symptoms;
・In chronic management, medication such as allopurinol or febuxostat can be considered to lower serum uric acid levels, with regular monitoring of liver and renal function;
・For recurrent severe attacks or large tophi affecting joint function, surgical intervention (such as tophus debridement or arthroscopic removal) may be considered.
2. Lifestyle Management
・Maintain a healthy body weight, limit alcohol consumption, reduce high-purine foods, and ensure adequate fluid intake;
・Regularly monitor serum uric acid levels to prevent recurrence.
3. Rehabilitation and Exercise Prescription (FITT-VP)
・Frequency: Engage in light to moderate exercise 3-5 times per week;
・Intensity: After acute inflammation subsides, start with isometric muscle exercises around the joint and range-of-motion exercises, gradually increasing resistance by about 10-20% per month;
・Time: Begin with 10-15 minutes per session, progressing to 30 minutes or more as tolerated;
・Type: Focus on low-impact exercises such as swimming, cycling, or light weight-bearing movements for the lower limbs; avoid excessive weight-bearing or intense activities during acute phases;
・Progression: Increase exercise volume and weight-bearing gradually as joint pain and inflammation improve, ensuring a stepwise enhancement of joint stability and muscle strength;
・Precautions: If joint swelling or significant pain occurs, reduce or stop exercising and seek medical advice if necessary.
4. Example of Individualized Training
・Weeks 1-2: Primarily focus on small-range ankle joint exercises (dorsiflexion and plantar flexion), 8-10 repetitions per session, 2-3 sets per day.
・Weeks 3-4: With improved range of motion, incorporate resistance band exercises for lower-extremity muscle strengthening (e.g., resisted ankle dorsiflexion), 10-15 repetitions per session, 2-3 sets per day.
・Long-term Adaptation Phase: Once function is stable, add light aerobic activities (e.g., walking on flat ground or using a stationary bike) at moderate intensity for 20-30 minutes.
This report is a reference analysis based on the patient's current medical history and imaging findings. It should not substitute for in-person evaluation or professional medical advice. If you have any questions or if your condition changes, please consult a specialist and undergo further examination.
Tophaceous gout of the posterior talocrural joint
