Swelling in one, or both of the knees is not uncommon in people from teenagers to the elderly. The knees are some of the most interesting joints in the body because they contain an especially complex configuration of soft tissue alignments. People notice swelling in the knees because of injury, force trauma, and even nutritional factors. Swelling can occur within the knee joints themselves, or between the skin and bony structures. It can be accompanied by pain, or a general feeling of stiffness and pervasive warmth. Athletic And Occupational Injury The vast majority of swelling in the knees is a result of blunt trauma exerted laterally on the joint. Knees are designed with triangular ligament structures that allow the legs to bend along the lines of the body, and support the body's weight. In activities where there is the possibility of non-vertical collision, or “side strikes,” the ligaments of the knees can detach and initiate joint swelling. The tissues of the knees are semi-vascular, so any trauma can cause the gradual accumulation of water, mucous, blood, and other fluids around the joint. Most injuries of this sort are felt right away, and accompanied by a noticeable “pop” feeling and sound. The action is followed by excruciating pain and almost immediate swelling patterns. In some cases, like repetitive motion work-related stress, this type of knee injury is undetected. Swelling will appear and gradually get worse. This is a sign that the tiny sacks of fluid, or bursa, supporting the knee have been aggravated enough to signal fluid retention. Arthritis Whether genetically induced, or aged and use-related, knee arthritis is notorious for causing swelling. Arthritis shifts the natural shape of the knee's bony structures causing friction and an immune response. As the condyle ends of the bones change, they prompt the body to rush fluids into the knee to curb inflammation and pressure. Radical arthritic immune responses can produce extreme swelling with a decreased ability to move the knees in a full range of motion. Extreme pain often accompanies this type of chronic swelling. Tearing Aside from sports and work-related ligament tears, the “floating” structures of the knee can be damaged and cause swelling. One of the most notorious parts of the knee this happens to is the meniscus. The meniscus is a cup-shaped cartilage pad that is responsible for absorbing weight-bearing functions of the knee. During actions like lifting heavy objects and walking with loads, the meniscus slides freely between the joint in a forward and backward motion. Sometimes, quick motions and weight pressure will not allow the meniscus to slide back into its normal position. As a result, the bones of the knee will shear and cut the meniscus. This trauma will cause a fluid retention response and reduce the normal range of motion in the joint. Meniscus tears are very common for people who lift weights and spend time on ladders. Nutritional Factors Gout and psudeogout can cause great inflammation and swelling in the knee. These conditions arise from poor dietary habits, or the presence of chemicals in the body. Like kidney and urinary tract stones, tiny crystals can form within the knee joints. There is no way for the knee to transport these structures away from the joint, so they continue to build. Even a microscopic accumulation of gout and psudeogout crystalline deposits will interfere with the knee's function. This will sometimes result in incredibly voluminous and obstructive water and fluid gain within and around the knees. Slight fluid gain around the knees is acceptable for active individuals. Most joint fluid retention is not painful and will dissipate with anti-inflammatory OTC medication, therapeutic braces, and a reduction in activity. Excessive “water on the knee” is an indication that there is a major injury, or physiological problem. Without seeking expert medical advice about fluid in and around knees, a person risks exasperating existing damage and permanently losing degrees of function. Some problems with knees that cause swelling will require surgery and movement therapies. Most, if caught in time, will only require education about adopting different methods of movement and enjoying favorite physical activities.