Synovial membranes from "non-inflammatory" arthropathies featured neovascularisation and inflammation intermediate between normal and OA synovium. These results expand previous findings that mechanical joint injury may lead to a mild-to-moderate synovitis.

A simple, rapid screening method using alizarin red S stain and ordinary light microscopy to detect microcrystalline or noncrystalline calcium phosphate salts was used on wet drop preparations of synovial fluids. This proved to be helpful in detecting apatite crystal clumps and small calcium pyrophosphate dihydrate (CPPD) crystals missed by polarized light. The staining was positive in 100% of synovial fluids from patients later proven to have apatite and/or CPPD deposition diseases. Apatite and CPPD crystals were commonly found together in the same fluids. In addition, some synovial fluids from patients with osteoarthritis, renal failure dialysis, rheumatoid arthritis, and gout also exhibited positive staining. The correlation of positive alizarin red S staining with radiologic evidence of osteoarthritis suggests that apatite crystals might be related to articular cartilage degeneration in different rheumatic diseases. (1,2).Recently, apatite crystals have been found in synovial fluid from patients with osteoarthritis (OA) and, more rarely, in patients with otherwise unexplained arthritis (3,4). However, individual apatite crystals are not identifiable under ordinary or polarized light because of their minute size (750-2,500 A in length) (5). Their precise identification requires electron microscopic techniques or x-ray diffraction analysis. A semiquantitative radioisotopic technique using 14C ethane-1 hydroxy 1, I diphosphonate (EHDP) binding to detect hydroxyapatite crystals in synovial fluid has been introduced by Halverson and McCarty (6,7). Although large amounts of apatite crystals tend to form aggregates which may appear as shiny but not birefringent clumps in synovial fluid, these shiny clumps are not always observed. At least some similar clumps might be due to protein OJ cell debris (4).These observations had led us to search for simpler methods of apatite identification in joint effusions. This study reports the use of a calcium stain, alizarin red S, on wet drop preparations of synovial fluid as a screening test to detect apatite crystals. The alizarin tests were performed on synovial fluid from patients with a variety of different joint diseases. The presence of alizarin stained clumps correlated with the findings of apatite crystals by transmission electron microscopy (TEM) and with the radiologic grade of OA. MATERIALS AND METHODSAlizarin red S staining techniques. Alizarin red S stain (Harleco, Gibbstown, NJ), 2% solution in distilled water,

Objective. In this in vivo study, we investigated changes in the proteins that coat monosodium urate (MSU) crystals in human synovial fluid samples and rat air pouch fluid samples obtained sequentially during periods of active and resolving inflammation, in order to evaluate whether in vivo findings are consistent with hypotheses on roles of protein coating based on in vitro findings.Methods. Crystals from patients with gout were isolated from joint fluids with acute inflammation, and subsequently from the same joints at the time inflammation was resolving. Crystals were also obtained using the rat subcutaneous air pouch model. Immunogold was used to label proteins coating MSU crystals, for light microscopy (LM) and transmission electron microscopy (TEM) studies.Results. Dense immunogold-silver labeling for IgG was observed under LM on crystals from fluid with acute inflammation, whereas other proteins (apolipoproteins [Apo], fibronectin, fibrinogen, albumin) were not labeled significantly. Apo B became strongly positive on crystals as the inflammation subsided,

Fifty synovial fluid (SF) samples from patients with various types of arthritis were examined promptly after joint aspiration and after storage at room temperature (22°C) or at refrigerator temperature (4°C) for 1 hour, 2 hours, 3 hours, 6 hours, 1 day, and 3 days, then weekly for 3 weeks and monthly for 2 months. We found that the leukocyte count (white blood cell [WBC] count) decreased within a few hours. In 4 SF samples from patients with mild inflammation (initial range 3,150-6,200 WBC/mm3), the WBC count decreased into a "noninflammatory" range (<2,000/mm3) within 5-6 hours. In 3 of 5 SF samples that on the first day were found to be laden with crystals of calcium pyrophosphate dihydrate (CPPD), the crystals were much less abundant and were difficult to recognize by the next day. CPPD crystals dissolved completely in all SF samples by 3-8 weeks of the study. Monosodium urate crystals remained detectable throughout the 8 weeks of study, but they became smaller, less birefringent, and less numerous with time. Clumps of apatite-like crystals persisted for several months. Most SF samples initially negative for apatite-like crystals remained negative over time. New, artifactual crystals, including alizarin red S-positive clumps or star-shaped arrays, plate-like structures, positively birefringent Maltese crosses, and hematoidin crystals, developed with time. Because of these observations, we urge prompt examination of SF specimens to avoid the problems of misdiagnosing borderline inflammatory fluids, missing CPPD crystals that dissolve with time, or over-interpreting the findings because of the new, artifactual crystals.Analysis of synovial fluid (SF) is widely recognized as an important part of the diagnostic evaluation of patients with arthritis and joint effusion (1,2). It is particularly important in diagnosing septic arthritis and crystal-induced arthritis (3), and it allows classification of joint diseases into characteristic groups identified by inflammatory, "noninflammatory," or bloody effusions (4). Examinations of SF samples are often delayed for several hours, and when samples are sent for consultational evaluation, the analysis may be delayed for days. There have been few studies of any of the possible consequences of such delays (3, and our concern was that delayed interpretation might lead to important alterations in the constituents of the SF that could change the clinical impression or diagnosis.To explore this possibility, we sequentially examined 50 SF specimens over a 2-month period. We studied fresh samples of SF and then studied the same fluids after storage at room temperature or in the