The Density and Distribution of Capillaries Around a Synovial Cavity

Abstract

The interpretation of trans‐synovial fluxes requires a knowledge of the number of capillaries present around the joint cavity, and their depths below the surface of the joint lining. Measurements of capillary numbers, depths and dimensions were therefore carried out by light microscopy on synovial tissue sections from five rabbit knees. In addition the surface area of synovial tissue lining the joint was estimated, and the thickness of the synovium measured. Synovial capillary density was found to be uneven, with respect to both anatomical location in the joint cavity and depth below the synovial surface. The large area of synovium over areolar or adipose tissue was highly vascular (67000–83000 capillaries.cm−2 section; mean intercapillary distance 35–55, µm; 228–329 cm2 endothelium.cm−3 synovium). The small area of synovium over tendons was of very low vascularity (2000 capillaries.cm−2 section). From these data and a previous estimate of net filtration capacity, mean synovial endothelial conductivity was estimated as ∼ 16 x 10−7 cm.s−1.mmHg−1. The depth distribution of the capillaries was extremely skewed, with a sharp peak at 6–11 µm depth. The rapid decay in capillary density at depths 〉 6–11 µm was partly due to an uneven density of capillaries within the synovium itself; and partly due to a lower density in subsynovial tissues. It was concluded that most synovium has a rich capillary bed which is very superficially located and that the depth of periarticular tissue which is effective in exchange processes with the joint cavity is less than 25 µm.

Vascularization and Innervation of the Canine Wrist Joint Synovial Membrane.

“…These studies have reported that vascular density varies with the type of synovium and the most vascular synovium is the areolar type. A high capillary density within 25 ,um of the synovial surface has also been noted in rabbit (Knight and Levick 1983) and human (Wilkinson and Edwards 1989) synovium. The present observations using vascular corrosion cast allowed us to demonstrate a three dimensional distribution pattern of the blood vessels in the Synovial fold.…”

Lymphatic drainage in the muscle and subcutis of the arm after breast cancer treatment

“…Since the rate of lymph and interstitial fluid formation is closely coupled to capillary filtration rate in the steady state [24,25], the findings indicate a faster generation of interstitial fluid by capillary filtration in muscle. While differences in the Starling forces may contribute to this, the most obvious explanation is that the numerical density of blood capillaries in skeletal muscle (300-1,000/mm 2 ) is *3 times that in adipose subcutis [26][27][28]. The difference in k and the greater mass of muscle indicates that the subfascial compartment generates most of the lymphatic 'load' (volume per unit time) reaching the axilla.…”

Influence of Actin Cytoskeleton on Intra-articular and Interstitial Fluid Pressures in Synovial Joints

“…The vertical depth of the tip was calculated as h ⅐ sin , where was the angle of insertion (ϳ45°) and h the distance advanced obliquely, as read from the micromanipulator scale in micrometers. Since the arithmetic mean thickness of rabbit synovium in the suprapatellar pouch is 16 -19 m, and that of the subsynovium is ϳ100 m (Knight and Levick, 1983;Levick and McDonald, 1989a), measurements taken at tip depths of Ͻ10 m were classified as synovial interstitial pressures and those at 20 -35 m were classified as subsynovial interstitial pressures. The region between 10 and 20 m was ignored due to the uncertainty over tissue type near the synovium/subsynovium boundary during a blind penetration.…”