Background/Purpose: Arthrocentesis has emerged as a highly valuable diagnostic and therapeutic intervention for rheumatic diseases since first standardized by Hollander in the 1950’s. Successful arthrocentesis of the knee, to decompress the effusive knee and provide objective material for laboratory analysis, is contingent upon obtaining sufficient synovial fluid. As a Quality Improvement process within the Division of Rheumatology, we introduced constant compression of the knee during arthrocentesis and determined whether quality measures including aspiration success and fluid volume were improved.

Methods: This Quality Improvement project was performed within the Rheumatology Division at the University of New Mexico Health Sciences Center and assessed quality improvement of intra-procedural constant compression during knee arthrocentesis in terms of overall success, outcome and quality among individual patients. All patients undergoing knee arthrocentesis for therapeutic/diagnostic reasons were sequentially included and classified prior to the procedure as to either non-effusive (dry) vs. effusive knees as per physical examination. The more effective conventional lateral knee arthrocentesis techniques alone were undertaken rather than the less effective medial approaches. Initially the patient underwent arthrocentesis with an elastomeric knee brace placed loosely around the knee with syringe exchange maneuvers performed as required to decompress large effusions if present. Upon termination of synovial fluid return using the conventional method, the elastomeric brace was securely tightened without disturbing either arthrocentesis needle or syringe and arthrocentesis was again attempted. Quality outcome measures included: 1) trace yield of synovial fluid with initial arthrocentesis, 2) diagnostic yield of synovial fluid (defined as ≥0.25 ml) with and without compression, 3) total synovial yield in milliliters (ml) with and without compression. Pierson Chi squares two by two table analysis was performed on categorical data calculating both p values and confidence intervals. Measurement data was analyzed using the Student t-Test calculating both p values and confidence intervals as well.

Results: There were no complications encountered by the 113 patients in the cohort including, but not limited to infection, significant bruising or other hemorrhage. At least trace synovial fluid was obtained in 83.3%. However, diagnostic synovial fluid (at least 0.25 ml) was obtained in 31.9% without compression and 46.6% with compression (p=0.0001, z for 95% CI= 1.96, Pierson). Absolute volume of arthrocentesis fluid yield without compression was 3.7±6.6 ml versus 6.6±13.0 with compression (p=0.018, 95% CI -5.5881 <-2.9< -0.2119) corresponding to a mean 2.9±6.1 ml (80%) increase in synovial fluid yield. In the subset of 87 patients with a palpably dry knee at least trace synovial fluid was obtained in 79% of patients. Diagnostic synovial fluid (at least 0.25 ml) was obtained in 13.8% without compression and 42.5% with compression (p=0.0001, z for 95% CI= 1.96). In the palpably dry knee absolute volume of arthrocentesis fluid without compression was 0.3±0.9 ml versus 1.1±2.1 ml with compression (p=0.001, 95% CI -1.2801 <-0.8< -0.3199). This corresponds to a mean 0.8±1.6 ml (266%) increase in synovial fluid yield. In the subset of 26 patients with a palpably effusive knee, at least trace synovial fluid was obtained in 100% of patients. Diagnostic synovial fluid (at least 0.25 ml) was obtained in 96% without compression and 100% with compression (p=0.2, z for 95% CI= 1.96). In the palpably effusive knee absolute volume of arthrocentesis without compression was 15.4±14.1 ml versus 25.7±15.9 ml with compression (p=0.008, 95% CI –18.4686 <-10.3< -2.1314) corresponding to a mean 10.3±9.2 ml (67%) increase in synovial fluid yield.

Conclusion: The quality and success of knee arthrocentesis can be markedly improved through the application of constant compression using a circumferential knee brace. The overall success of diagnostic/therapeutic arthrocentesis can be significantly increased with markedly improved fluid yield compared to conventional arthrocentesis in both the clinically non-effusive and effusive knee. The increased synovial fluid return and arthrocentesis also provides additional value through confirmation of accurate intraarticular needle placement. As complete arthrocentesis has been demonstrated to improve subsequent intraarticular injection outcomes, constant compression with an elastomeric knee brace is a simple and economical quality improvement maneuver that can be incorporated into clinical musculoskeletal practice and injection clinics.  

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/improvement-in-knee-arthrocentesis-via-constant-compression/