11th June 2024

A 45-year-old lady presents with a 1-year history of left knee pain

A 45-year-old lady presents with a 1-year history of left knee pain. She reports this has progressively worsened over the last year. She is finding it difficult to weight-bear, mobilising with the help of a frame. She also reports a 4-month history of anorexia, night sweats and weight loss. She was born and raised in Eritrea and is an avid traveller. She has been in the UK for 8 months.

An MRI of the knee shows narrowing of the joint space and severe subchondral erosion and destruction. T1-Flair showed hyperintense lesions with complete destruction of the cartilage medially with periarticular enhancement suggestive of a collection. Joint aspiration showed WCC of 10,000/mm3, gram stain and microscopy negative.

Which investigation is most likely to lead to a diagnosis?

Select the SINGLE most appropriate option from the list below. Select ONE option only.