SWOLLEN KNEE IN A RUNNER - A DIAGNOSTIC PUZZLE.

Introduction: Ankylosing Spondylitis (AS) is a chronic and progressive inflammatory disease that affects the axial skeleton. Peripheral joints and extra-articular structures may also be affected. It usually presents in men in their second or third decade and leads to reduced spinal mobility and back pain. Ankylosing Spondylitis presents a strong association with histocompatibility antigen HLA-B27. Case Report: We present the case of a 43-year-old male, a runner, who presented to the orthopedics yard with complaints of disabling pain and swelling of the right knee. MRI showed inflammatory adhesions and inflamed synovial folds. Four days later he presented to the rheumatology department for further investigations. The knee ultrasound revealed significant fluid accumulation with synovial proliferation and Doppler signal grade two. Examination of the fluid drawn from the knee articulation showed no crystals and no positive culture, ruling out gout and septic arthritis. Differential diagnosis also excluded Reactive Arthritis, as laboratory results revealed negative anti-Chlamydii and negative anti-Mycoplasma antibodies. Anamnesis revealed an episode of lumbar pain four years prior, interpreted as an L5-S1 discopathy, and treated with Nonsteroidal anti-inflammatory drugs (NSAIDs). The clinical exam indicated flattening of the lumbar lordosis, positive patellar reflex, and global tumefaction of the right knee. The pelvic X-ray revealed bilateral sacroiliitis stage II/III. Blood work demonstrated raised ESR (70) and raised C-reactive protein (6.8), pointing towards a case of marked inflammatory syndrome. The patient did not complain of limited mobility or pain in the spine but soon began to develop dactylitis and tendinitis, suggestive of AS. HLAB27 positive, and findings of active and chronic lesions demonstrated by the MRI confirmed the diagnosis. Discussions : Underdiagnosed inflammatory lumbago is a reason for late diagnosis of ankylosing spondylitis (8 years on average). This delay is often responsible for the occurrence of ankylosing lesions. The atypical onset of AS can represent a diagnostic challenge, therefore it is important to have this thought especially in young men with musculoskeletal disorders. Monoarthritis can have multiple causes that require a differential diagnosis, among them being AS. In this case, the patient's hobby, running, and the atypical onset of the symptoms represented diagnostic pitfalls, and the subsequent appearance of other extraskeletal manifestations outlined a diagnostic puzzle. Conclusions: This case underscores the importance of conducting a detailed anamnesis when it comes to a young patient with a history of back pain, as it may be the key to early diagnosis and treatment. [ABSTRACT FROM AUTHOR]