Joint aspiration: The dry tap
- W Neal Roberts, Jr, MD
W Neal Roberts, Jr, MD
- Chief of Rheumatology
- University of Lousiville
- Curtis W Hayes, MD
Curtis W Hayes, MD
- Professor of Radiology
- Virginia Commonwealth University
- Section Editor
- Daniel E Furst, MD
Daniel E Furst, MD
- Section Editor — Treatment Issues in Rheumatology
- Professor of Rheumatology, University of Washington, Seattle
- Professor of Rheumatology, Washington University of Florence, Florence, Italy
- Professor of Rheumatology, University of California in Los Angeles (Emeritus)
- Director of Research, Pacific
In occasional patients, a joint that has obvious fluid on physical examination yields a “dry tap” during diagnostic arthrocentesis, even after the needle has been redirected and is clearly in the joint space. This problem comes up with surprising frequency with respect to the knee and also occurs with joints that are more difficult to tap, such as ankle and shoulder. The proper approach to a dry tap in an individual patient has to take into account, above all, the degree of suspicion of a septic joint. When joint fluid is necessary for diagnosis, consideration should be given both to the differential diagnosis of the causes of a dry tap and to a change in technique which this differential implies.
CAUSES OF A DRY TAP
There are three major explanations for a dry tap after extraarticular placement of the needle tip is excluded (table 1):
●Mistaken physical diagnosis
●Blockage of the bevel of the needle by plica, fat, or debris
●Very high viscosity fluid or true lipoma arborescens
- Roberts WN, Hayes CW, Breitbach SA, Owen DS Jr. Dry taps and what to do about them: a pictorial essay on failed arthrocentesis of the knee. Am J Med 1996; 100:461.
- Feller JF, Rishi M, Hughes EC. Lipoma arborescens of the knee: MR demonstration. AJR Am J Roentgenol 1994; 163:162.
- Hardaker WT, Whipple TL, Bassett FH 3rd. Diagnosis and treatment of the plica syndrome of the knee. J Bone Joint Surg Am 1980; 62:221.
- Schumacher HR Jr. Synovial fluid analysis and synovial biopsy. In: Textbook of Rheumatology, Kelly WN, Harris ED Jr, Ruddy S, Sledge CB (Eds), WB Saunders Company, Philadelphia 1993. p.562.
- Katz WA. Knees and legs. In: Diagnosis and Management of Rheumatic Diseases, 2nd, Katz WA (Ed), JB Lippincott, Philadelphia 1988. p.153.
- Manger B, Kalden JR. Joint and connective tissue ultrasonography--a rheumatologic bedside procedure? A German experience. Arthritis Rheum 1995; 38:736.