The quadriceps, the short-form reference for the quadriceps femoris, is the group of four muscle structures positioned at the front of the thigh that are commonly described as the "quads." The quadriceps extends from below the patella (kneecap) on the tibia (shin), over the entire length of the thigh. The quadriceps is also connected to the patella by way of the quadriceps tendon. Three of the four quadriceps muscles originate at the top of the femur and the fourth, the rectus femoris, is connected to the pelvis. The quadriceps is a large, stable muscle structure whose function is to permit the extension of the knee, and as a result the quadriceps is crucial to the movement of the leg.
The quadriceps is so integral a part of human movement that it is frequently injured, although rarely in a fashion that causes permanent muscle damage. The exposure of the quadriceps to sports injury is governed by two separate factors: the stability and structure of the entire leg structure, and the nature of the athletic activity.
The action of the quadriceps, powering the extension of the leg from the front of the thigh, is countered by the hamstring tendon and muscle complex at the back of the thigh. The hamstrings are attached to the pelvis underneath the gluteal muscles of the buttocks, and like the quadriceps, the hamstrings extend past the knee joint to the tibia. The hamstrings provide flexion to the knee, permitting the lower leg to bend as well as facilitating the ability of the hip to be extended. All movement of the leg, whether walking, running, or jumping, require the harmonious and balanced action of the quadriceps and the hamstrings.
Imbalances between the relative strengths or flexibility of the hamstring versus the quadriceps are a major contributing factor in quadriceps injuries. It is a generally accepted proposition of sport science that the relative strength of the quadriceps to the hamstring should be a ratio of 3:2. This balance ensures that neither muscle group dominates the other; one of the chief causes of knee injury generally, and anterior cruciate ligament (ACL) injury in female athletes in particular, has been the structural imbalance between these muscle groups. When the hamstring is unable to counter the power of the quadriceps, the ACL is subjected to excessive stress.
In the quadriceps itself, such imbalances are manifested as a pull or a tear to the muscle fibers. A pull, also known as a muscle strain, is an over-extension of the muscle fibers, which may involve tiny or micro tearing of the structure. A tear is a progressive injury from that of a pull, where the muscle structure sustains a significant separation of the fibers and a resultant loss of muscle function. The most serious form of a muscle tear is a rupture, which is the complete severing of muscle fibers.
Overuse and repetitive motion are the most common causes of quadriceps pulls or tears. All running, cycling, and kicking sports athletes such as soccer and rugby often experience quadriceps tears or pulls. Weightlifting is another sport where quadriceps pulls and tears are common, especially in the lifting of
Another common injury of the quadriceps occurs in jumping sports such as basketball or in athletics events such as the high jump, where the athlete repetitively places stress upon the quadriceps in the generating of lift. The quadriceps tendon, the connective tissue between the quadriceps muscle and the patella, and the patella tendon, leading from the patella to the tibia, are the frequent sites of the tendinitis known as "jumper's knee." This condition causes significant and often immobilizing pain to the athlete. Jumper's knee may also cause swelling in and around the tendon.
The most serious tear that can be sustained to the quadriceps is that of a quadriceps tendon rupture. This form of injury can occur as a progression from an existing pull or tear that an athlete sustains, or it may occur spontaneously when the quadriceps sustains a sudden overloading force, such as a effort to drive the leg forward with as much power as possible. The loss of the connection between the quadriceps and the patella creates a buckling effect in the knee, because the leg cannot be straightened. The only treatment for such an injury is surgical repair, where the quadriceps tendon is physically reconnected to the patella.
Most quadriceps pull or tear injuries are resolved through the application of RICE (rest/ice/compression/ elevation) treatments, initiated immediately after the onset of any pain. For more serious occurrences, nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, or more powerful prescription medications may assist in the recovery process.
The recovery from a quadriceps pull or tear should be a gradual one. The return of the athlete to regular training must be managed to ensure both the compete recovery of the injury, as well as an emphasis on flexibility, stretching, and the balance between the relative strengths of the quadriceps and hamstring structures.