18th January 2024

Differential diagnoses

Crystal arthropathy – this includes gout and pseudogout, which are common causes of an acute hot joint. Their clinical features are extremely difficult to differentiate from septic arthritis as the patient may even have a fever/raised inflammatory markers. Joint aspiration is vital in these cases, showing uric acid crystals (negatively birefringent) in gout; and calcium pyrophosphate crystals (positively birefringent) in pseudogout.
Reactive arthritis – this is often confused with gonococcal septic arthritis but is a different condition entirely. Reactive arthritis is an inflammatory process usually triggered by a systemic genitourinary or gastrointestinal infection. In reactive arthritis, the joint aspirate is sterile. It may present in a mono- or poly-articular manner.
Injury – this is important to consider prior to a joint aspiration, particularly if the patient is unable to give an accurate history, e.g. due to young age or confusion. If in doubt, perform a radiograph prior to aspiration.
Lyme arthritis caused by infection with Borrelia burgdorferi – this is not a true septic arthritis as it is a systemic infection which results in joint inflammation. It usually causes polyarthralgia and joint inflammation many months after the original infection.

Complete Guide to Clinical Genetics ST3 Application and Recruitment (2027)

Written by Medibuddy. Last updated: October 2026. Clinical Genetics is

Recruitment paused: NHS England is not running Clinical Radiology ST3+ recru

Written by Medibuddy. Last updated: October 2026. If you’re planning

Our mobile app allows you to access your interview and exam question banks wherever you are.