A tear (rupture) of the tendon between the lower pole of the kneecap (patella) and the tibial tuberosity (Tuberositas tibiae) is called a patella tendon rupture. The tendon can rupture due to various force effects. The patellar tendon rupture is a rare injury, but its faulty or incorrect treatment could lead to permanent damage or further tears. Younger people are most frequently affected by a rupture of the patella tendon, who expect a high degree of mobility and activity in everyday life, which is why the rupture must always be treated by a physician. With proper treatment, the prognosis for a patellar tendon rupture is generally very good.
Anatomy
The quadriceps femoris muscle on the front of the thigh stretches the leg in the knee joint. The four muscles end at which the kneecap is embedded and extends to the shin. Below the kneecap, this tendon is also called the patellar ligament (Ligamentum patellae).
The tendon fixes the patella and serves as a central pivot point (hypomochlion) during flexion in the knee joint. The majority of the tendon fibers originate from the end tendon of the rectus femoris muscle, one of the four thigh muscles. These fibers also radiate into the patella and partially cross it. To the side of the patella, fibers of the other three muscles (musculus vastus medialis, musculus vastus lateralis, musculus vastus intermedius) are located, which tend to pass the patella. The patella tendon is absolutely necessary for a powerful extension in the knee joint.
Patella tendon rupture
Rupture of the patella tendon can be caused by forces acting indirectly or directly. The patellar tendon rupture is usually caused by over-tension trauma against resistance or strong tension in the flexed position of the knee joint. Such an accident mechanism is particularly common in sports such as tennis or skiing.
Due to the relatively small lever between the pivot point of the knee joint and the kneecap, the patella tendon has a very large cross-sectional load, up to over 1000 kg/cm2 in heavy persons. In rare cases, cortisone injections into the knee joint can lead to a rupture of the patella tendon. It is assumed that a tendon that has not yet been pre-damaged will only rupture in the rarest of cases.
The probability of a patella tendon rupture increases with existing previous damage. Degenerative damage is found, for example, in people with Ehlers-Danlos syndrome, butterfly lichen (lupus erythematosus), chronic renal failure, diabetes mellitus, arterial occlusive disease or after surgery. In adulthood, ruptures of the patellar tendon are most frequently found at the transition from the lower pole of the patella to the tendon, as this appears to be an anatomical weak point.
Often the patellar tendon rupture is additionally combined with a bony tendon rupture, which means that a bone fragment of the patella breaks off at the tendon due to excessive traction. In children and adolescents, a rupture of the patellar tendon usually occurs further down near the point of attachment of the tendon to the tibia (near the tibial tuberosity). Direct violence, such as cuts or lacerations, can also cause a rupture in the middle of the patellar tendon. A tear can also occasionally occur due to irritation of the patella tendon.
