A person may easily injure his knee joints because they are the primary weight-bearing joints of a person's body. Injuries may be prevented by strengthening the muscles around the knee joint and by avoiding repetitive movements of the knee such as bending, jumping and twisting. Symptoms of a knee injury include pain, warmth and tenderness around the knee, clicking sounds and an inability to flex, extend and bear weight on the knee.
Types
The knee is actually composed of three different joints. There is a joint between the shin bone, or tibia, and the thigh bone, or femur. The second knee joint is between the femur and the kneecap, or patella. The third joint in the knee is between the tibia and the smaller bone of the leg, the fibula.
Function
The primary function of the tibiofemoral knee joint is to bear the weight of the body and extend and flex the knee. The patellofemoral knee joint protects the anterior surface of the tibiofemoral joint and improves the movement of the quadriceps muscle during knee extension, according to Sandra Shultz, Ph.D., and colleagues, in their book "Examination of Musculoskeletal Injuries." The function of the tibofibular joint is to decrease the movement of the tibia and fibula when the leg twists at the knee.
Features
The knee joints are composed of connective tissues such as ligaments, menisci and bursae. Ligaments hold the bones of the knee joints together. The menisci lying on top of the tibia absorb shock and stabilize and lubricate the tibiofemoral joint. The bursae surrounding the knee joints are pillow-like sacs filled with fluid and help to prevent friction when the knees are in motion. The knee joint is also filled with synovial fluid, lubricating the knees.
Muscles
The muscle group acting on the knee joints to straighten the knees is the quadriceps. The quad muscle is actually composed of four different muscles converging into a single common tendon, the patellar tendon. This tendon completely surrounds the patella as it crosses the knee joints. The hamstring muscle group is made up of three different muscles which flex or bend the knees.
Injuries
Common injuries to a person's knee joints include bursitis or an inflammation of a bursa. Bursae become inflamed from excessive kneeling, bending, running and cycling. The anterior cruciate ligament can be injured if a person lands off-balance while the legs are straight or when he cuts or pivots quickly while the foot is planted on the ground. A menisci may tear when squatting or twisting at the same time. Menisci may also tear simply by getting up from a chair because menisci weaken with age, according to American Academy of Orthopaedic Surgeons.
References
- "Examination of Musculoskeletal Injuries"; Sandra Shultz, Ph.D., Peggy Houglum, Ph.D., and David Perrin, Ph.D.; 2005
- Sports Injury Clinic: Proximal Tibiofibular Joint Dislocation
- Ortho Info: American Academy of Orthopedic Surgeons: Meniscal Tears
