This article discusses two rare cases of intra-labral pigmented villonodular synovitis (PVNS) of the hip. The hip joint represents the second most common location of pigmented villonodular synovitis, second to the knee [1]. The majority of hip PVNS cases either diffusely involve the synovium or are focal lesions within the joint. The lesions and synovium show foci of low signal intensity related to hemosiderin deposition, a finding that differentiates PVNS from other causes of synovial proliferation. Our case report presents two rare manifestations of PVNS lesions localized within the hip labrum. This presentation could easily be mistaken for a cyst by imaging modality. Despite the rarity of this condition, we highlight the importance of questioning the possibility of intra-labral PVNS, when patients have persistent hip pain not responding to therapy and atypical imaging findings. Highlighting this rare presentation is crucial for establishing the correct diagnosis, guiding treatment, and obtaining the best clinical outcome.

OBJECTIVE: The current study aims to report the radiologic and clinical appearance of a rare anatomical variation of the knee medial synovial plica along with its response to conservative and surgical treatment.
METHODS: This report portrays a 29-year-old male patient with anteromedial gradual onset right knee pain, aggravated when descending stairs or prolonged sitting. Physical examination revealed medial parapatellar local tenderness, a palpable click in this area when the knee was extended, and hamstring tightness. Magnetic resonance imaging showed a duplicated medial plica, characterized by a high-intensity signal of the infrapatellar fat pad medial portion, after which a presumptive diagnosis of medial plica syndrome was proposed. After conservative treatment failure, the patient underwent standard knee arthroscopy that revealed a superior low profile and an inferior high profile medial plica, and hypertrophy of the medial portion of the infrapatellar fat pad. Both plicae and fat pad were resected with a mechanical shaver until no contact between the femoral trochlea and the fat pad was observed during full range of motion. At 4 weeks postoperatively, symptoms completely resolved, and the patient was allowed to return to full activity with no recurrences at 1 year follow-up.
CONCLUSIONS: The current study presented a rare anatomical variation of the knee medial synovial plica that was symptomatic and recalcitrant to conservative treatment. This case report may be useful for radiologists and orthopaedic surgeons to differentiate this special plica type and consider its response to conservative and surgical treatment during patient management.

Synovial osteochondromatosis (SOC) is a rare, benign condition of unknown etiology characterized by the formation of cartilaginous loose bodies. This often leads to early osteoarthritis with decreased range of motion and pain. Clinical presentation most often is reported as monoarticular pain affecting the knee or less commonly the hip shoulder or elbow. Diagnosis can be confirmed on x-ray imaging where the characteristic synovial bodies will be identified. Management with early debridement of the synovium will often be curative but more complex cases may require further surgical management. We present a 33-year-old male presented with localized left knee pain. Given the history of new-onset pain, left knee x-rays were obtained that revealed a displaced patella with multiple ossific densities around the left knee which were suspicious for a new diagnosis of SOC. Due to its nonspecific symptoms and imaging, the diagnosis of SOC is often delayed or missed. Therefore, prompt diagnosis and treatment are important in order to avoid irreversible cartilage destruction in the joint, prevent the development of chronic pain, and reduce the risk of malignant transformation.

Complex degenerative tears of the medial meniscus in the knee are usually treated using meniscectomy. However, this procedure increases the risk of osteoarthritis, while other treatments aimed at meniscal repair remain challenging due to the high possibility of failure. The use of synovial mesenchymal stem cells (MSCs) is an attractive additional approach for meniscal repair, as these cells have high proliferative and chondrogenic potential. In this case report, we surgically repaired a complex degenerative tear of the medial meniscus and then transplanted autologous synovial MSCs. We evaluated clinical outcomes at 2 years and assessed adverse events. We enrolled patients with clinical symptoms that included a feeling of instability in addition to pain caused by their complex degenerative tears of the medial meniscus. Two weeks after surgical repair of the torn meniscus, autologous synovial MSCs were transplanted onto the menisci of five patients. The total Lysholm knee score, the Knee Injury and Osteoarthritis Outcome Scale scores for \"pain,\" \"daily living,\" \"sports activities,\" and the Numerical Rating Scale were significantly increased after 2 years. Three adverse events, an increase in c-reactive protein, joint effusion, and localized warmth of the knee were recorded, although these could have been due to the meniscal repair surgery. This first-in-human study confirmed that the combination of surgical repair and synovial MSC transplantation improved the clinical symptoms in patients with a complex degenerative tear of the medial meniscus. No adverse events occurred that necessitated treatment discontinuation. These findings will serve as pilot data for a future prospective study.

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