We present the case of a previously well 18 year old female who presented with an acute onset swollen painful right ankle with an overlying non-blanching purpuric rash. There were no associated systemic features. Ankle joint aspirate grew Neisseria Meningitides. She was treated with intravenous third generation cephalosporin's and surgical washout of the joint with improvement. Primary meningococcal arthritis (PMA) is rare and mostly associated with the knee joint. Presentation of meningococcal disease in this manner is easily missed or misdiagnosed as gonococcal disease or overlying cellulitis.

Primary meningococcal arthritis is a rare form of septic arthritis. It can be misdiagnosed as an overlying cellulitis or as a gonococcal rash. Physicians should be aware of the possibility of this microorganism presenting as a septic arthritis, and understand the importance of joint aspiration at the centre of diagnosis.

The extension facet angle (EFA) of the medial compartment of the knee has been implicated as a potential mechanical cause for anteromedial knee osteoarthritis.

We developed a novel sagittal plane flexion osteotomy of the medial tibiofemoral compartment. We then performed a cadaveric study to study the effect of the osteotomy on the intra-articular knee pressures under axial load mimicking the stance phase of gait. A Tekscan K400 pressure sensor was inserted submeniscally into the joint and 700N applied using an Instron machine. A topographical map of the pressure areas was then assessed pre- and post-osteotomy for the 10 cadaveric knees specimens.

We found that the intra-articular pressures are greatest in the anteromedial compartment in the native knee and after the osteotomy the area of highest pressure moves posterolaterally spread over a greater surface area.

We conclude that a flexion osteotomy of the medial compartment reduces intra-articular knee pressures concentrated anteromedially in full extension and may be beneficial in patients with an elevated EFA with anteromedial symptoms.