However, because both types of cartilage lack a significant blood supply, isolated injuries to these structures are not likely to result in bloody fluid. Both meniscal and chondral (articular cartilage) injuries can result in a localized collection of fluid. It facilitates movement while also protecting the integrity of the bones. The other - articular cartilage - provides a smooth glassy surfacing at the ends of many bones.
The medial (innermost) meniscus and lateral (outermost) meniscus are composed of fibrocartilage and serve to create a better fit for the femur and tibia at the knee and act as shock absorbers. There are two types of cartilage in the knee (view image). This is known as synovitis and can result from overuse. If the synovium becomes inflamed, causing pain and swelling, it too can cause joint effusion. Damage to the highly vascularized synovial membrane can also result in hemorrhage into the joint. Trauma to the knee that causes fracture or tearing of ligaments - such as the ACL or PCL - can cause that fluid to be bloody. Some of these may be from sudden trauma, while others may be due to more chronic conditions.
THE IMPLICATIONS OF KNEE-JOINT EFFUSION: BLOODY VERSUS NON-BLOODYĪny number of pathologies can result in fluid buildup.
Possible causes of edema include trauma from a contusion (bruise), soft tissue injury such as muscle strains or inflammation of a bursa.
