The patella, commonly known as the kneecap, is a small, flat, triangular bone located at the front of the knee. It is a component of the complex knee joint, enabling various movements and providing protection.
Anatomy and Location
The patella is classified as a sesamoid bone, meaning it is embedded within a tendon. It is the largest sesamoid bone in the human body. This bone sits within the quadriceps tendon, which extends from the thigh muscles, and connects to the tibia (shin bone) via the patellar ligament. Its position is anterior to the femur (thigh bone) and tibia, articulating with the femur to form the patellofemoral joint. The patella has a triangular shape, with its pointed apex facing downwards and its broader base at the top where the quadriceps tendon attaches.
Function and Importance
The patella enhances the mechanical advantage of the quadriceps muscle group. By acting as a fulcrum, it alters the angle at which the quadriceps tendon pulls on the tibia, increasing the leverage and efficiency of knee extension. This allows for powerful straightening of the leg, necessary for activities such as walking, running, jumping, and climbing.
Beyond its role in movement, the patella also serves as a protective shield for the front of the knee joint. Its position safeguards underlying knee structures, including the end of the femur, from direct impact or trauma. This dual function of improving mechanical efficiency and offering protection is important for maintaining knee health and mobility.
Common Conditions Affecting the Patella
Several conditions can affect the patella, leading to pain and impaired knee function. Patellar dislocation occurs when the kneecap slips out of its normal position, often moving to the side of the knee. This injury results from a direct blow, a sudden twisting motion of the knee, or anatomical predispositions.
A patellar fracture is a break in the kneecap. These fractures can happen from a direct fall onto the knee, a strong impact, or a forceful quadriceps muscle contraction that pulls the bone apart. Symptoms include pain, swelling, and difficulty or inability to straighten the leg.
Patellofemoral pain syndrome (PFPS) describes pain located under or around the kneecap. It is commonly known as “runner’s knee” and is associated with overuse, muscle imbalances, or improper kneecap tracking within its groove. Pain typically worsens with activities like climbing stairs, squatting, or prolonged sitting with bent knees.
Patellar tendinitis, also referred to as “jumper’s knee,” is an inflammation or irritation of the patellar tendon, which connects the patella to the shin bone. This condition is an overuse injury, seen in athletes involved in sports that require repetitive jumping or running. The repetitive stress creates tiny tears in the tendon, leading to pain and tenderness just below the kneecap.