2024-04-172024-04-172024-03-21https://hdl.handle.net/20.500.12503/32734Background: Synovial osteochondromatosis is a benign, uncommon, and interesting disorder that presents challenges in diagnosis and treatment. It is a complication of the synovial membrane of joints, tendon sheath, and bursae that can cause dysfunction most commonly in the knee, hip, or shoulder that has the potential of transforming into chondrosarcoma. While the exact etiology of a primary synovial osteochondromatosis is still in question, hypotheses point toward the metaplasia of the synovial membrane and the detachment of cartilaginous fragments as potential causation. The cause of secondary synovial osteochondromatosis is associated with an underlying joint pathology or condition that triggers development such as osteoarthritis, rheumatoid arthritis, or traumatic joint injuries Patients with this condition usually present with a history of pain in the joint affected, swelling, crepitus, and limited range of motion (ROM).The pain is usually aching in nature and is exacerbated by weight-bearing activities such as prolonged periods of walking or standing. Case Information: A 62-year-old female with a past medical history of hypertension and hypothyroidism presented to the clinic with a chief complaint of bilateral knee pain and effusions, which was diagnosed as osteoarthritis based on clinical exam and past X-rays. The patient had been experiencing moderate relief from bilateral steroid injections that were administered approximately every four to six months. As for diagnostic imaging, she had two MRI scans of her left knee; the first in 2020 and the second in 2023. The differential diagnosis formulated in the clinic after the MRI scan (Fi [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10705034/figure/FIG1/]was pigmented villonodular synovitis (PVNS), rheumatoid arthritis (RA), or synovial chondromatosis. Conclusions: Although synovial osteochondromatosis is generally a benign condition, transformation to chondrosarcoma is still a possibility. Imaging may assist in identifying the loose bodies floating in the joint space, but this becomes much more difficult if the loose bodies are radiotransparent (chondromatosis). Calcified nodules (osteochondromatosis) are relatively less difficult to view on X-ray. T2 weighted MRI imaging can help identify synovial hyperplasia which can help clue clinicians in with other physical exam findings. Although an arthroscopy with histopathology is the gold-standard diagnostic modality, it is important to keep in mind that one or even two different types of imaging modalities may not be sufficient for synovial osteochondromatosis to make the differential. As seen in our case, it took three years after the pain from the onset of chondromatosis for suspicion to arise on MRI. Sometimes patients may not be so fortunate by the time it is noticed and, although uncommon, the formation of chondrosarcoma may already be in progress. If left untreated, patients can also develop severe osteoarthritis. Clinicians must not hesitate to diversify the imaging modalities in which they order, as a diagnosis may become more apparent in one versus the other. Another lesson to take from our case is to stay vigilant in regard to who can present with synovial osteochondromatosis. Although our patient did fit the expected location of the disease (larger joint, the knee in this case), she did not fit the expected gender or age group in which these processes arise.enposter