Intra‐articular pressure characteristics of the knee joint: An exploratory study

Abstract

Inflammation-predominant osteoarthritis is an important clinical type of osteoarthritis, with synovitis suggested as its distinct pathophysiology. We investigated whether the synovium's mechanical properties in knees differed by osteoarthritis and other clinical parameters through retrospectively analyzing intra-articular pressure-volume characteristics. We analyzed 60 knees that were administered intra-articular corticosteroids while undergoing pressure monitoring. McMurray's test, pain complaints at end-range knee flexion, Kellgren-Lawrence classification from standing anteroposterior radiographs, and suprapatellar effusion from ultrasound constituted clinical parameters.Pressure-volume profiles-phasic changes in pressure by volume infusion, the volume of Phase 1-the potential volume of the synovial space, the pressure at 45 ml infusionintra-articular pressure at a standardized volume, and the slope of Phase 2-synovial stiffness were compared with clinical parameters. All graphs were biphasic. Knees with suprapatellar effusion or radiologically definite osteoarthritis (Kellgren-Lawrence grade ≥2), had a lower Phase 1 volume. Knees with definite radiographic osteoarthritis also showed higher pressures at 45 ml and Phase 2 slopes (171.11 ± 94.35 mmHg and 5.08 ± 3.07 mmHg/ml, respectively) than those without (101.88 ± 58.12 mmHg and 2.84 ± 1.27 mmHg/ml, respectively). The Phase 2 slope was higher for knees with positive provocative tests than in those with negative provocative tests, although not statistically significant. The synovium stretched earlier in knees with effusion or radiologically definite osteoarthritis. Intra-articular pressure and synovial stiffness were significantly higher in patients with radiologically definite osteoarthritis. The synovium's mechanical characteristics are altered by osteoarthritis of the knee joint. Intra-articular pressure characteristics could be utilized for synovial evaluation clinically.

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“…(4). In addition, due to the fact that SKJ usually has no special early clinical symptoms other than paroxysmal swelling and pain, most patients do not pay attention to the treatment, resulting in disease progression into a severe stage at the time of diagnosis (5). At this time, SKJ will not only be accompanied by severe pain and symptoms such as severe limitation of joint motion and quadriceps femoris atrophy, but also the invasion of articular cartilage due to changes in synovial membrane morphology, increasing the possibility of disability (6).…”