A torn patella tendon is when the tendon between the front thigh muscles and the lower part of the patella tears partially or entirely. The term patella tendon rupture is also used as a synonym for patella tendon tear.
Tearing of the patella tendon is a relatively rare disease that can occur with existing previous damage to the tendon or due to lifting effects. It mainly occurs in younger people and should be treated by a doctor to avoid a subsequent limitation of movement as a late consequence.
Anatomically, this tendon is indispensable for stretching in the knee joint, as it is the starting point for the overlying extensor muscles of the thigh. This is mainly the four-headed extensor muscle (Musculus quadriceps femoris), which is located on the front of the thigh and whose four parts together lead to the patellar tendon at the lower pole of the patella. In addition, the patella tendon fixes the patella in its slide bearing and serves as a deflection pulley during flexion in the knee joint.
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Causes of the torn patella tendon
Tearing of the patellar tendon usually occurs spontaneously due to excessive over-tensioning of the leg against resistance or when the knee is tensed in the flexed position. Such accident mechanisms often occur during sports such as skiing or tennis.
However, a completely healthy tendon is hardly likely to tear. In most cases, there is another pre-damage, which increases the probability of a tear during such an event. These are, for example, degenerative changes of the tendon as part of other concomitant diseases, irritation of the patella tendon, previous operations, or, in rare cases, cortisone injections into the knee joint.
In children and adolescents, the tear of the patella tendon usually occurs at the transition of the tendon to the tibia. In adults, the tear is usually located further up, at the lower transition of the tendon to the patella.
Sometimes a bone fragment of the kneecap is torn off in addition. This is called a bony tear of the tendon.
In the middle, the tendon usually only tears in the context of injuries with direct violent impact.
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The torn patella tendon usually manifests itself as a sudden pain in the affected person. In addition, the loss of stability makes it difficult to walk and stand, and reduces the strength of the knee joint. The active extension in the knee joint is usually limited or no longer possible. In addition, it can be observed that the kneecap is higher than the opposite side (patella elevation), and a dent can often be felt at the site of the tear.
A further phenomenon that occurs with a torn patella tendon is that the kneecap slides up when the thigh muscles are tensed or when the knee joint is bent, as the torn tendon no longer has sufficient fixation to the tibia.
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Diagnosis of a torn patella tendon
During palpation of the torn patellar tendon, both the elevation of the patella and the palpable dent are noticeable. The tendon can also no longer be palpated in its continuity.
The exact nature of the tear can be easily assessed on an X-ray image. It is also possible to see whether or not there is an additional bony tear of the tendon. In addition, the lateral image allows other diagnoses with similar symptoms (e.g., patellar rupture) to be excluded, which is of fundamental importance for further therapy.
The diagnosis is finally confirmed by means of an ultrasound examination. In the case of more complicated variants of patellar tendon rupture or to exclude concomitant injuries to the knee joint, further imaging diagnostics may be necessary. These include, for example, an MRT of the knee. Especially in the case of partial tears of the patellar tendon, an MRI of the knee can provide valuable information about the condition of the remaining patellar tendon.
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Therapy of the torn patella tendon
A torn patella tendon causes severe pain but can heal if treated properly.
In the acute phase of a torn patella tendon, one can try to relieve the pain with ice and support the leg.
If the tendon is completely torn, it should always be sutured together again by means of a surgical procedure. An exception will be if the patient is in acute danger of death or if there is also extensive soft tissue damage. In this case, it is better to wait a little and stabilize the overall situation of the patient before performing surgery for the torn patella tendon.
However, only strains or small tears of the tendon can be treated without any surgical intervention, which does not cause any relevant reduction in strength.
Depending on the location of the torn patella tendon, a different procedure is used.
In the case of a deep patellar tendon tear at the transition to the tibia, which frequently occurs in children and adolescents, the tendon suture is performed, and the tendon is also fixed to the bone with a suture anchor.
McLaughlin cerclage is usually used to protect the newly fixed tendon from mechanical overload. This is a wire sling that is fixed between the kneecap and the tibia to relieve the tendon during the healing process. This enables early treatment to restore the full range of motion of the knee joint as quickly as possible. After three to six months, this wire loop is removed again, unless it has already loosened or detached before.
It is also important to ensure that the previous length of the tendon is restored, as too tight a fixation can lead to late consequences such as restricted mobility or arthrosis.
Surgery for a torn patella tendon is performed under general anesthesia and usually takes no longer than 30 to 45 minutes.
Complications that can occur during this operation are, as with all surgical measures, bleeding in the area of the knee joint, possible infection, and injury to adjacent structures.
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All in all, the healing phase of a torn patella tendon takes a relatively long time since tendons are among the types of tissue that are less well supplied with blood. Immobilization is, therefore, of utmost importance for the healing process.
Various aids are used for this, such as a so-called stretching orthosis or a thigh tutor splint. The extension orthosis is an aluminum splint that is padded from the inside and keeps the knee bent at a certain angle. The thigh tutor splint is a plaster cast that extends from the groin to the ankle and also keeps the knee bent at a defined bending angle.
With such an aid, the leg can be fully loaded immediately after the operation; only the knee flexion should be performed gradually. For the first two weeks, the knee joint should be flexed at a maximum of 30 degrees, followed by an increase to 60 and 90 degrees every two weeks. About seven weeks after the operation, the knee should be moved without splinting, if no other factors speak against it.
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Despite immobilization, it is crucial to start knee training early on in order to regain the full range of motion and avoid further complications caused by immobilization. These are, for example, thromboses or emboli events, soft tissue damage due to splinting and regression of the musculature (atrophy) due to lack of movement.
Physiotherapy is very well suited for the early mobilization of the knee and the prevention of these complications. With this method, the affected muscle groups are specially trained, and exercises for knee mobility adapted to the respective healing step are performed.
Many affected persons report a limitation of knee extension, but this can usually be remedied by specific training.
For a good prognosis of a torn patellar tendon, it is crucial to start mobilization early on despite immobilization in order to regain the previous range of motion. In most cases, this is also successful.
However, factors that can delay the healing process are too early or inappropriate full loading of the knee, which can cause the wire loop to break off, or postoperative wound infections. In the case of degenerately damaged tendons, the tendon may also tear again.
If no negative factors are present, however, the torn patella tendon will heal completely, and there will be no further restrictions in everyday life or other sporting activities.
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