The present study introduces a new method to measure the SPE with the use of MRI. The evaluation of the functional engagement of the patella with the femoral trochlea in the sagittal plane can serve as a supplementary tool to the existing methods of evaluating patellar height, and may help to better identify the cases where inadequate engagement is recorded despite the absence of patella alta, so that the need for tibial tuberosity osteotomy may be re-assessed.

AEI is a new index to measure LPD. It can be obtained in all cases because it is obtained from two different MRI views. The normal value is close to 1. It can be used to measure patellar instability on the axial plane in patients with OPI, especially in the most severe cases.

We describe the third case of prosthetic infection due to Erysipelothrix rhusiopathiae. The patient, a 68-yearold woman, had had total knee arthroplasty 12 months before diagnosis. She had been in contact with swine at home. We review the seven previous reports of septic arthritis due to E. rhusiopathiae. CASE REPORTA 68-year-old woman was referred to the orthopedic ward for total replacement of the right knee due to severe internal condyle osteonecrosis. She had a medical history of gout, chronic eczema of the lower limbs, and alcoholism with consequent cognitive disorders. A tricompartmental posterior stabilized cemented knee artroplasty, containing gentamicin, was performed. The patient did not experience any problems during the first 6 months of follow-up. The international knee scoring (IKS) system score was 80/200 before surgery and increased to 163/200 6 months after surgery. Soon after, the patient complained of eczema-like skin lesions on the lower limb, involving the site of surgical incision. During this period, neighbors reported seeing the patient feeding her neighbor's swine through the wire enclosure. The patient's general practitioner prescribed an intramuscular corticosteroid because of intense itching. Within weeks of receiving this treatment, she complained of swelling and pain in the right knee and received amoxicillinclavulanate. A radiography of the knee was normal. One month later, seropurulent fistulization of the right knee was observed at the distal end of the surgical incision site, and the patient was referred to the hospital. On admission, flexion of the right knee was reduced to 90°. The patient was not febrile. No cardiac murmurs, skin rash, or lymph node enlargement was found. The peripheral white blood cell count was 6,100 cells/mm 3 , and the C-reactive protein concentration was 74 mg/liter. Radiography revealed advanced osteolysis of the tibia, femur, and patella. Blood cultures remained sterile. Twelve months after right knee arthroplasty, surgical arthrotomy was carried out, yielding a sanguinepurulent "chocolate-like" fluid. Synovial resection was performed, revealing large geodes resulting from osteolysis in the femur, tibia, and patella. The prosthesis was removed and replaced by a vancomycin-and gentamicin-impregnated spacer. Intravenous rifampin and vancomycin treatment was started. Eleven peroperative samples were sent to the laboratory. All Gram staining tests were negative. Cultures were grown on blood agar plates under aerobic and anaerobic conditions and on chocolate agar plates incubated under 5% CO 2 . Cultures were negative on day 2. On day 4, four samples yielded pinpoint colonies. Microscopic observations of these first cultures revealed thin, short, cylindrical Gram-positive rods. Subcultures were set up for potential confirmation of Lactobacillus or Corynebacterium. These subcultures yielded enterococcus-shaped colonies on day 2. Bacteria were confirmed to be rod shaped but were longer and thinner than those observed in the initial cultures. On the basis of t...

Results clarified the relation between degenerative meniscus lesions and osteoarthritis, in terms of meniscal incompetence. Meniscal extrusion should be seen as an arthrogenic degenerative meniscus lesion. We recommend a management strategy based on terrain and imaging data (X-ray and MRI), with the aim of providing patient relief while conserving cartilage.

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