Correspondence

Acute Monoarthritis

N Engl J Med 1994; 330:221-222January 20, 1994

Article

To the Editor:

The excellent review article on acute monoarthritis by Baker and Schumacher (Sept. 30 issue)1 contains an erroneous statement. In discussing how to differentiate acute arthritis of the elbow from acute olecranon bursitis by physical examination, the authors state that “in septic olecranon bursitis, the swelling and erythema can extend nearly to surround the elbow; if full flexion is retained, there is unlikely to be a true arthritis.”

In fact, both acute arthritis and acute bursitis hurt during flexion. The critical point in distinguishing the two processes, in addition to the local findings, is whether passive extension is unimpaired -- a feature of subcutaneous bursitis but not of arthritis. These findings may relate to shifts of cavitary pressures and tissue stretching with motion. Intraarticular pressures in the elbow and in the knee are lowest at 30 to 75 degrees of flexion2. Additional flexion or extension sharply increases the cavitary pressures. In contrast, pressures in the olecranon and prepatellar bursae are lowest from full extension to approximately 60 degrees of flexion3. Further flexion steeply increases the pressures. Furthermore, in the olecranon bursa (and probably in the prepatellar bursa, since they have a similar anatomical arrangement), the bursal sac is compressed and deformed in flexion and resumes its relaxed ovoid configuration in extension4. I can recall more than one time when a careful assessment of passive extension helped establish the source of inflammation around the elbow and knees.

Juan J. Canoso, M.D.
New England Medical Center, Boston, MA 02111

4 References

1. 1

   Baker DG, Schumacher HR Jr. Acute monoarthritis. N Engl J Med 1993;329:1013-1020
   Full Text | Web of Science | Medline

2. 2

   Eyring EJ, Murray WR. The effect of joint position on the pressure of intra-articular effusion. J Bone Joint Surg Am 1964;46:1235-1241
   Web of Science | Medline

3. 3

   Canoso JJ. Intrabursal pressures in the olecranon and prepatellar bursae. J Rheumatol 1980;7:570-572
   Web of Science | Medline

4. 4

   Saini M, Canoso JJ. Traumatic olecranon bursitis: radiologic observations. Acta Radiol 1982;23:255-258
   Web of Science

Author/Editor Response

The authors reply:

To the Editor: We thank Dr. Canoso for picking up an error that crept into our manuscript during editing. The paragraph in question started out by emphasizing the importance of looking for evidence of a flexion contracture (the loss of full ability to extend the elbow) as a clue to joint effusion. Unfortunately, the meaning was reversed during the final editing process to correct our grammar, and we missed the change. We take some consolation from the fact that this gaffe allowed Canoso to expand in such a scholarly way on the mechanisms involved. We hope that anyone who tore out this article as a review will correct it; we will correct the error in the many reprints that we are sending out.

H. Ralph Schumacher, Jr., M.D.
University of Pennsylvania School of Medicine, Philadelphia, PA 19104

Daniel G. Baker, M.D.
Medical College of Pennsylvania, Philadelphia, PA 19129