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Patellar Tendon Rupture
Patellar tendon rupture is an rupture of the tendon
that connects the patella to the tibia. The patellar
tendon attaches to the tibial tubercle on the front
of the tibia just below the front of the knee, and
is connected to the bottom of the patella, above
which are attached to the quadriceps tendon,
followed by the quadriceps muscle, large muscles on
the front of the thigh. This structure allows the
knee to flex and extend, allowing use of basic
functions such as walking and running.
When rupture occurs, the patella loses support from
the tibia and moves toward the hip when the
quadriceps muscle contract, hindering the leg's
ability to extend. This means that those affected
cannot stand, as their knee buckles and gives way
when they attempt to.
Causes of Patellar Tendon Ruptures
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Injury
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A very strong force is required to tear the patellar
tendon.
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Falls. Direct impact to the front of the knee from a
fall or other blow is a common cause of tears. Cuts
are often associated with this type of injury.
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Jumping. The patellar tendon usually tears when the
knee is bent and the foot planted, like when landing
from a jump or jumping up.
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Tendon Weakness - A weakened patellar tendon is more
likely to tear. Several things can lead to tendon
weakness.
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Patellar tendonitis. Inflammation of the patellar
tendon, called patellar tendonitis, weakens the tendon.
It may also cause small tears.
Patellar tendonitis is
most common in people who participate in activities that
require running or jumping. While it is more common in
runners, it is sometimes referred to as "jumper's knee."
Corticosteroid injections to treat patellar tendonitis are
typically avoided in or around the infrapatellar tendon.
Injections around this articular tendon have been linked to
increased tendon weakness and increased likelihood of tendon
rupture.
Chronic disease. Weakened tendons can also be caused by
diseases that disrupt blood supply. Chronic diseases which
may weaken the tendon include:
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Chronic renal failure
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Hyper betalipoproteinemia
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Rheumatoid arthritis
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Systemic lupus erythmatosus (SLE)
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Diabetes mellitus
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Infection
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Metabolic disease
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Steroid use. Using medications like corticosteroids and
anabolic steroids has been linked to increased muscle
and tendon weakness.
Symptoms of patellar tendon rupture include:
Knee X-rays are the first imaging studies that are obtained
and can be very helpful. When the patellar tendon ruptures,
the patella shifts superiorly because of muscle contraction
of the quadriceps muscles. This shift in the patella
position is called “patella alta.” X-rays also evaluate the
knee for any other injuries that can present similarly to a
patellar tendon rupture such as a fracture. If any doubt
remains after physical examination and X-rays, an ultrasound
or magnetic resonance imaging (MRI) can be performed.
Ultrasonography is a safe, inexpensive and rapid test that
can detect a tendon tear. However, the test is technician
dependent and in some facilities is not a reliable
diagnostic test. MRI is also a safe test but is more
expensive and takes longer to perform. In addition,
availability of MRI’s can be limited in emergency rooms and
a doctor’s office. However, an MRI can also evaluate any
other potential problems in the knee such as ligament or
cartilage injury. In the vast majority of athletes who have
suffered a patellar tendon rupture, an MRI is not indicated
as the diagnosis is made with X-rays and physical
examination. However, in the case of partial tears, chronic
tears or an unusual presentation, an MRI can be a useful
diagnostic tool.
Surgical repair of the torn tendon is recommended. If the
tear is treated non-operatively, the patient will rarely
have the ability to extend the leg and ambulate normally
without assistance. Surgical repair, while not an emergency,
should be performed soon after the injury occurred. This
allows for an easier repair before a significant
accumulation of scar tissue. Most surgeons perform a direct
repair of the tendon if it is torn in the middle. If the
tendon is torn off of the bone, several different techniques
can be utilized such as reattaching the tendon to the bone
with a combination of sutures and bone tunnels. Regardless
of technique, the goal of surgical repair is to
re-approximate the tendon ends in a secure fashion to allow
it to heal.
If the patellar tendon is not repaired soon after the injury
(within 5-6 weeks), surgical repair can become more
difficult and have suboptimal results. If the tendon cannot
be repaired back to itself, a reconstruction can be
performed with a graft from donor tissue (allograft) or
tissue taken from another part of the patient’s body (autograft).
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