Related Experiment Video
Updated: Jun 19, 2026

Knee Arthrocentesis in Adults
Published on: February 25, 2022
THE HYDROGEN ION CONCENTRATION OF JOINT EXUDATES IN RHEUMATIC FEVER AND OTHER FORMS OF ARTHRITIS
1Hospital of The Rockefeller Institute for Medical Research.
Abstract:
1. The hydrogen ion concentration of joint exudates aspirated from patients ill with acute rheumatic fever, arthritis of undetermined origin, and bacterial arthritis was determined. The hydrogen ion concentrations of the joint exudates from patients with acute rheumatic fever approximated the normal reaction of blood, varying from pH 7.27 to 7.42. Exudates from patients with arthritis of undetermined origin varied in pH from 7.33 to 7.47. The pH of a joint effusion occurring in a patient with myocardial insufficiency was 7.34. Bacteriologically, all of these fluids were sterile by ordinary means of cultivation. An exudate aspirated from a knee infected with Staphylococcus aureus had a pH of 6.69, while that from a patient having an arthritis due to Streptococcus hoemolyticus was also acid, having a pH of 6.19. 2. Since a definitely acid medium is necessary for the liberation of free salicylic acid and since all of the joint fluids from patients with acute rheumatic fever were slightly alkaline, no free salicylic acid could possibly exist in such joint fluids following the administration of salicylates.
Related Concept Videos
Rheumatic Heart Disease I: Introduction
Rheumatic Heart Disease II: Clinical Manifestations and Diagnostic Studies
Inflammatory Response II: Inflammatory Exudate and Tissue Repair
The typical wound exudate is odorless, transparent, straw-colored, thin, and watery. Exudate, however, can differ depending on the state of wound healing. Likewise, the exudate's...
Polyprotic Acids
Structural Joints: Synovial Joints
Acute Inflammation III: Local and Systemic Effects