The knee is surrounded by several types of tendons, which help govern interaction between the thigh, kneecap, and calf. While multiple tendons make up the knee area, the most commonly known are the quadriceps tendon, the illiotibial band, the hamstring tendon, and the patellar tendon, which is also known as the patellar ligament. Each type of knee tendon serves a different purpose, but together they create the extensor mechanism that allows bipedal movement and controls knee extension and relaxation.
The first type of knee tendon, the quadriceps tendon, connects the thigh to the knee itself. The muscles of the thigh are known as quadriceps, and this tendon stretches from those muscles down to the upper part of the patella, or kneecap. The quadriceps tendon is relatively short, thicker at the top, and tapers to a shorter base, where it attaches to the patella.
From the patella, the thinner patellar tendon connects the kneecap to the calf. Specifically, this knee tendon joins the patella to the tibia bone in the lower leg, forming a short stretch of strong, elastic fibers that taper from the kneecap to the tibial tubercle, an oval knob at the top of the tibia. The bone-to-bone connection is the reason why the patellar tendon is also called the patellar ligament.
The longest type of knee tendon, the illiotibial band, extends from an upper thigh muscle to the outside of the knee. This muscle, the tensor fasciae latae, begins at the hip and tapers down to the long illiotibial band. The tendon then connects to the tibia and fibula. Together the tensor fasciae latae and the illiotibial band contribute to medial rotation in the hip and leg.
The last of the major tendons in the knee is the hamstring tendon. This knee tendon is most commonly known when referring to the process of hamstringing, or severing the hamstring tendons and muscles to cripple an opponent and render him unable to stand. The hamstring begins on the underside of the thigh, and connects the hamstring muscles in the back of the thigh to the tibia and fibula. The tension and extension provided by the hamstrings are crucial to most forms of bipedal motion.
The relative vulnerability of the knee area leaves the tendons open to injuries, which are common in sports. Knee tendons are also subject to tendinitis. The individual tendons can each suffer their own individual injuries due to location, age, injury, and general wear and tear — such as illiotibial band friction syndrome or patellar tendinitis.