Most of these symptoms are caused by stagnant blood in the muscles, fascia and other soft tissues. Venous blood sampling is a frequent adjunct to clinical testing, and the thicker veins near the medial elbow joint are usually selected for venipuncture. When the blood is drawn, the soft tissue is loose, the vein is too thick, and the elasticity is relatively large, resulting in easy bleeding in the process of hemostasis, with the blood remaining under the skin and generally only bruising and slight pain when pressing on the area. If the local bleeding does not stop and other fluids leak out, the fluids will penetrate deep into the fascia and muscle spaces, and these fluids will form a local inflammatory reaction, stimulating the surrounding soft tissues to become slightly inflamed as well. Inflammation usually leads to local adhesions of varying degrees, and when the soft tissues such as fascia and muscles slide during arm movement, the inflammation and adhesions will stimulate local painful symptoms.