The patella, also known as the kneecap or kneepan, is a thick, circular-triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as mice, cats, and birds, but not in whales, most reptiles nor amphibians such as frogs.
In humans, the patella is the largest sesamoid bone in the body. Babies are born with a patella of soft cartilage which begins to ossify into bone at about three years of age.
Due to its construction and function, the knee joint is a joint susceptible to damage. The knee joint consists of a large bone (the femur) in the upper leg and the shin bone (tibia) and calf bone (fibula) in the lower leg. To ensure a better joint between the bones of the lower leg and the upper leg, two menisci are located between the two halves of the leg. An inner (medial) and an outer (lateral) meniscus. The menisci are made from cartilage and as well as a control function, also have an important task in shock absorbance.
At the front of the knee is the kneecap or patella. The kneecap is embedded in the tendon of the knee’s large extensor. The bones of the upper and lower leg are held together by the capsula on the inside and outside, supported by ligaments (inner = medial collateral ligament) (outer = lateral collateral ligament). Right at the centre of the joint, the upper and lower leg are held together by the cruciate ligaments.
An acute injury to the knee occurs generally as a result of an uncontrolled movement (as a result of which the coordination between the upper leg and the lower leg fails to function), a collision with another player, or a fall. In any of these events, the ligaments and/or menisci may be damaged. Such injuries must always be examined by a sport physiotherapist, sport physician and/or orthopaedic specialist.
The primary functional role of the patella is knee extension. The patella increases the leverage that the tendon can exert on the femur by increasing the angle at which it acts.
It is attached to the tendon of the quadriceps femoris muscle, which contracts to extend/straighten the knee. The patella is stabilized by the insertion of the horizontal fibres of vastus medialis and by the prominence of the lateral femoral condyle, which discourages lateral dislocation during flexion. The retinacular fibres of the patella also stabilize it during exercise.
Patella allows uniaxial movements of legs that is back and straightning movements in 180 degree angle
The kneecap is prone to injury because of its particularly exposed location, and fractures of the patella commonly occur as a consequence of direct trauma onto the knee. These fractures usually cause swelling and pain in the region, bleeding into the joint (hemarthrosis), and an inability to extend the knee. Patella fractures are usually treated with surgery, unless the damage is minimum and the extensor mechanism is intact.