Non traumatic knee effusion: Pointer or Decoy? The commonly missed relationship of knee swelling with Lumbar disc disease: “The Dervan knee effusion sign”

Introduction: Knee pain and swelling are known amongst orthopedic surgeons as symptoms of a local pathology arising from the knee joint area. It is also often used by patients as an ‘umbrella term’. Although in most cases the causative pathology may be the knee joint itself, however, this umbrella term can cause prejudice among clinicians to look at only locally and not think of a lumbar pathology as a cause of knee pain and swelling. The objective of this pilot study was to make clinicians aware that causes knee pain and swelling may be beyond the anatomical confinements of the knee.

Material and Methods: This is a prospective study in which we evaluated consecutive patients with non-traumatic knee joint pain and effusion coming in our hospital from 1st January to 1st February 2020. Detailed history and clinical examination were taken. After ruling out obvious causes of non-traumatic knee pain and effusion in these patients, we included 38 patients based on our inclusion and exclusion criteria. Written informed consent was taken. They were evaluated for knee joint with radiographs and lumbar spine with radiographs and MRI. Arthrocentesis and synovial fluid evaluation were done.

Results: After synovial fluid examination, 2 patients were found to have subclinical inflammatory arthritis and were excluded out of the study. 36 of the 38 patients had a normal study on arthrocentesis. 2 out of these 36 patients had no abnormalities on spine MRI. Out of the remaining 34, 30 had disc degenerative disease at L45 or L5S1 (25 patient L4-5, 3 patient L5-S1, 4 patients with both L4-5 and L5-S1), 1 patient had a L34 disc degenerative disease, 3 patients had Grade 2 L45 spondylolisthesis with mild or no back pain.

Conclusion: Although a disc degeneration can be seen incidentally in many asymptomatic patients, based on our observations we think that causes like “autonomic” overload can be one of the unheard reasons of knee pain and effusion. The clinician must be aware of possible causes of knee pain and swelling beyond the anatomical confinements of knee and that lumbar spine pathology need also to be ruled out. The clinician must not let prejudice rule his clinical judgement. We don’t claim direct association of lumbar disc degeneration and knee pain and swelling in this study. Further studies are needed.