Knee osteoarthritis is a group of heterogeneous pathologies, but physical properties of stiffened synovia were less investigated. Intra-articular pressure changes according to volume infusion were investigated. Early synovial tension, high intra-articular pressure and stiffened synovium was observed in the presence of suprapatellar effusion or radiologically definite osteoarthritis. The development and consequences of stiffened synovia should be investigated further to elucidate their contributions to pain, disability, and disease progression, and in-clinic pressure monitoring could be utilized for its evaluation and treatment.

(A) A bovine nucleus pulposus (NP) explant bioreactor chamber. (B) In the volume controllable chamber, the NP tissue volume can be locked physically to an equilibrated pressure to prevent tissue swelling. Enzymes, biomaterials, and fluids containing cells or growth factors can be injected via the injection port. (C) Tissue can be measured biomechanically with a tensile tester.