The patellar ligament is a band of connective tissue that connects the patella, or kneecap, to the tibia. It forms a vital link in the musculoskeletal system of the lower limb and occasionally is the site of joint injury.
The patellar ligament is a thin, flat band of fibrous connective tissue about 2 to 3 inches (5 to 8 cm) long. It is located in the anterior region of the knee distal to the patella and anterior to the tibia. Like all other ligaments, the patellar ligament is made of dense regular connective tissue with its many collagen fibers running vertically.
On its proximal end, the patellar ligament arises from a wide region of the patella along its anterior and distal surfaces. It crosses the knee anterior to the joint capsule to insert to the tibial tuberosity of the tibia. The tendons of the vastus lateralis and vastus medialis muscles run parallel to the patellar ligament to connect these muscles to the tibia.
The patellar ligament is structurally continuous with the common tendon of the quadriceps femoris muscle, which connects the quadriceps to the patella. At birth, the patella is a small mass of cartilage found within the quadriceps tendon. Throughout early childhood this cartilage mass grows and ossifies, forming the patella and dividing the quadriceps tendon into two distinct structures. The distal structure becomes the patellar ligament as it now connects two bones together.
The patellar ligament plays an important role in the function of the knee joint and the lower limb as a whole. Contraction of the quadriceps femoris muscle group pulls the patella proximally toward the thigh through the quadriceps tendon. The patella, in turn, pulls on the tibia through the patellar ligament to extend the leg at the knee. This action is important for walking and running, but is especially strong during jumping and kicking.
A tear or rupture of the patellar ligament may result from stress to the ligament from jumping or from the impact during a fall. A partial tear will result in pain and irritation in the joint, and should be treated with rest or physical therapy. Complete tears result in the patella dislocating proximally toward the thigh and disabling the function of the knee. The only treatment for a complete tear is surgical reattachment of the ligament followed by rest and physical therapy.