Treatment options are limited in those with end-stage hemophilic arthropathy. Total knee arthroplasty (TKA) serves as a therapeutic and definitive treatment for hemophilic arthropathy, yet patients with hemophilia (PWH) are at increased risk of recurrent hemarthrosis following TKA. Standardized treatment of recurrent effusion (RE) after TKA has not been well-established. In this case presentation, a 62-year-old male with hemophilia A presented with RE after TKA for end-stage hemophilic arthropathy. After undergoing conservative management and an infectious workup, the patient was referred to interventional radiology for geniculate artery embolization (GAE). Four arteries near hemostasis were achieved. The patient's outcomes were evaluated using the Western Ontario and McMaster Osteoarthritis Index (WOMAC). At the three-month follow-up from embolization, the patient had an 83% decrease in the WOMAC score and no recurrence of effusion.

Intermittent hydrarthrosis (IH), also termed periodic synoviosis or periodic benign synovitis, is a rare cause of recurrent, self-limited joint effusion-most frequently involving the knee-with striking periodicity and complete intercritical recovery. Despite being recognized for decades, IH remains underdiagnosed and is often mistaken for palindromic rheumatism, crystal-induced arthritis, septic arthritis, proliferative synovial disorders, and autoinflammatory syndromes. Historical descriptions emphasized a benign, non-destructive course, minimal systemic inflammation, and a lack of specific biomarkers [1, 2]. More recent reports suggest that, in a subset of patients, IH may overlap with autoinflammatory mechanisms, including associations with MEFV mutations and clinical responses to colchicine or IL-1 blockade [3-6]. This narrative review synthesizes available evidence on terminology, clinical spectrum, diagnostic work-up, hypothesized pathophysiology, differential diagnosis, and therapeutic options, and proposes a pragmatic approach for clinicians.

Gout is a metabolic disorder caused by abnormalities in purine metabolism and/or impaired uric acid excretion. It is characterized by the deposition of monosodium urate crystals in joints or connective tissues, leading to recurrent episodes of acute arthritis. Gout can be categorized into two major types based on its etiology: primary and secondary. The majority of gout cases are associated with impaired uric acid excretion. The natural course of gout can be divided into three stages: (1) asymptomatic phase; (2) acute arthritis phase and intercritical phase; (3) chronic gouty arthritis and tophaceous phase. Acute gouty arthritis typically presents with sudden, severe joint pain, accompanied by redness, swelling, warmth, and tenderness of the affected joint and surrounding soft tissues. When large joints are involved, joint effusion may occur. Acute gouty arthritis often develops at night or in the early morning, is self-limiting, and usually resolves within two weeks. The most common site of acute gout flare-ups is the first metatarsophalangeal joint, followed by the midfoot, ankle, knee, wrist, fingers, and elbow joints. Acute gout attacks rarely affect the axial joints. Pain in these affected areas is often accompanied by limited function, significantly impacting a patient' s daily activities and quality of life. Uncommon sites of gout involvement, as well as gout with normal serum uric acid levels, can easily lead to misdiagnosis. Therefore, a comprehensive diagnosis requires a detailed medical history, physical examination, laboratory tests, and imaging studies. This case report describes a 19-year-old male who was admitted with recurrent anterior chest pain. The diagnosis at another hospital suggested ankylosing spondylitis. Physical examination revealed significant tenderness, redness, and swelling of the bilateral sternoclavicular joints, with local warmth and mildly restricted movement. MRI of the sacroiliac joints showed no significant abnormalities, and serum uric acid levels were normal. Chest dual-energy CT scans revealed multiple tophi in the sternum, bilateral clavicles, scapulae, multiple ribs, and along the edges of the sternum. Based on the patient' s medical history, physical findings, and imaging studies, a diagnosis of gout was confirmed. Treatment included urate-lowering therapy, pain management, and dietary adjustments. During a two-year follow-up period, the patient did not experience recurrent anterior chest pain, and multiple serum uric acid tests consistently showed levels below 300 μmol/L. Repeat chest dual-energy CT scans indicated significant reduction of tophi in the sternoclavicular joints and other affected areas.

PurposeTo establish MRI-based normative reference values for medial and lateral meniscal extrusion in asymptomatic Korean adults and to assess compartmental differences using absolute and proportional indices.MethodsA retrospective study of 38 independent knees from asymptomatic adults (mean age, 30.6 ± 4.5 years; 13 male, 25 female) was performed using a single-knee-per-subject protocol. Knees with trauma, ligament injury, significant effusion, meniscal tears, meniscotibial abnormalities, cartilage defects, or bone marrow lesions were excluded. Mid-coronal 1.5-T fat-suppressed proton density MRI was used to measure absolute extrusion and calculate the Meniscal Extrusion Index (MEI). Upper reference values were determined using mean + 2 SD and the 95th percentile. Compartments were compared using paired t-tests.ResultsMean medial meniscal extrusion (MME) was 1.86 ± 0.64 mm (95% CI, 1.65-2.07), with a mean + 2 SD of 3.13 mm and a 95th percentile of 2.84 mm. Mean lateral meniscal extrusion (LME) was 1.40 ± 0.59 mm (95% CI, 1.20-1.59), with a mean + 2 SD of 2.58 mm and a 95th percentile of 2.40 mm. Medial extrusion was greater than lateral extrusion (p = 0.0029; Cohen's d = 0.52). Mean medial and lateral MEI values were 22.5% ± 8.9% and 15.4% ± 9.2%, respectively.ConclusionsMild meniscal extrusion is present in structurally intact knees. Medial values approaching 3 mm and lateral values approaching 2.6 mm may represent normal anatomical variation. Interpretation should incorporate compartment-specific reference limits and proportional indices such as the MEI.

Mucoid degeneration (MD) of the anterior cruciate ligament (ACL) is an underdiagnosed condition marked by glycosaminoglycan infiltration within the ligament fibers. Its appearance on magnetic resonance imaging (MRI) can closely mimic an ACL tear, leading to diagnostic errors with major clinical consequences. We report a 54-year-old woman with a 6-month history of chronic knee pain and a sensation of heaviness, without any trauma. Physical examination showed a mildly positive anterior drawer test, interpreted as pain-limited rather than indicative of true instability, with a negative Lachman test. MRI revealed a thickened ligament with diffuse high signal intensity on proton density fat-saturated sequences, a celery stalk appearance on sagittal images, and a markedly thickened, crescent-shaped axial appearance of the hypertrophied ligament filling the intercondylar notch. The fibers appeared preserved and parallel to the Blumensaat line. Additional findings included near-complete filling of the intercondylar notch, intraosseous cysts at both the femoral and tibial ACL footprints, a Stoller grade III signal in the anterior horn of the lateral meniscus consistent with a meniscal tear, and a small joint effusion. The patient was managed conservatively with non-steroidal anti-inflammatory drugs and physiotherapy, with significant pain reduction and near-complete recovery of knee extension at six to eight weeks of follow-up. This case illustrates the imaging features that distinguish mucoid degeneration from ligamentous rupture on MRI, since misdiagnosis can lead to unnecessary surgery.

A male in his 70s with a remote history of a left total knee arthroplasty presented with acute left knee pain and swelling. He was a farmer with significant exposure to domestic and feral swine. CT of the knee showed a large complex left knee effusion and knee aspiration was concerning for infection. He underwent a debridement, antibiotics, and implant retention (DAIR) surgical procedure. Synovial fluid and operative cultures ultimately yielded Erysipelothrix rhusiopathiae, likely acquired from his animal exposures. He completed six weeks of intravenous daptomycin, followed by oral cefadroxil to complete a total of six months of antimicrobial therapy from the time of surgery. He had an excellent functional outcome with no recurrent infection at two years.

A 13-year-old boy presented with acute right knee pain, significant effusion, and a complete loss of active extension following a football injury. Radiographs demonstrated patella alta and increased density within the infrapatellar fat pad. Intraoperative exploration revealed a rare "triple injury" triad: a displaced inferior pole patellar sleeve fracture, a distal patellar tendon avulsion from the tibial insertion, and near-complete medial and lateral retinacular disruption. Surgical reconstruction was performed using suture-tape fixation with anchors for the patellar sleeve, tendon reinsertion utilizing Krakow sutures with screw augmentation, and primary retinacular repair. Following a structured postoperative rehabilitation program, the patient achieved an excellent functional outcome with restored full range of motion. This case highlights a complex multilevel extensor mechanism disruption in a skeletally immature patient and the surgical approach used for anatomical restoration.

Arthrogenic muscle inhibition (AMI) is a key neurophysiological mechanism that impairs voluntary quadriceps activation following total knee arthroplasty (TKA), potentially limiting functional recovery despite technically successful surgery. This review aims to synthesize current evidence on the neurophysiological mechanisms underlying AMI and to propose a mechanism-based rehabilitation framework targeting these inhibitory processes.