case_images: PMC10629506_01
case_images: Comparative images: (A) Two sets of ankle radiographs (MRI A-1, Plain XR A-2) AP and lateral views first in 2018 showed mild ankle joint effusion (red arrow) and small tibial plafond subchondral cystic changes (yellow arrow). (B) 2022 follow-up radiographs (Plain XR B-1, MRI B-2) showed progressive changes with multiple large subchondral cysts involving the ankle joint opposing articular surfaces (blue arrows) as well as secondary osteoarthritis with osteophyte formation (green arrow) and reduced ankle joint space. Ankle MRI-selected images coronal PD FS are illustrating the progression of the articular pathology, increase the number of subchondral cysts.
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case_images: Physical examination was unremarkable without any effusion or other findings suggestive of hemarthrosis; labs results showed normal platelet count, prothrombin time (PT), and activated partial thromboplastin time (aPTT); plain ankle radiography did not show any definite significant bone or articular pathology (Figure 1A); depending on these findings, there was no suspicion of an acute injury like hemarthrosis, and the patient was discharged with pain killers.  Ankle MRI showed 2018 mild ankle joint effusion and synovitis, with focal mass-like synovial proliferation noted at the anterior ankle recess, showing mild enhancement and blooming artifacts (Figure 1A). The images (Figure 1B) again demonstrated the same subarticular cystic-like changes with no interval changes.
case_images: MRI of the ankle joint: sagittal T2WI, sagittal gradient sequence and coronal PDWI, show intra-articular synovial low signal intensity (yellow arrow) demonstrating blooming artifact on the gradient sequence (red arrows) in the anterior and posterior recess of the ankle joint consistent with blood degradation products related to repeated episodes of hemarthrosis. Again, secondary osteoarthritic changes are noted with multiple cystic changes/geodes with surrounding marrow oedema. Findings are consistent with siderotic chronic synovitis.
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case_images: Tibiotalar hemophilic arthropathy with opposing subarticular pseudocyst formation and chondromalacia was observed (Figure 2). 