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Introduction
The knee extensor mechanism is essential to
stand and to walk. It is composed of the
quadriceps muscle and its tendon, the patella,
and the patellar tendon inserted to the anterior
tibial tuberosity (ATT). Those three structures
are continuous and form a single biomechanical
entity allowing active extension of the knee.
Acute quadriceps tendon rupture, transverse
and displaced patellar fracture and acute
patellar tendon rupture interrupt the continuity
of the knee extensor mechanism. A common
clinical finding in those three pathologies is an
inability to actively extend the knee. Quadriceps
and patellar tendon ruptures are rare and 28%
are initially undiagnosed [23]. History, clinical
exam, radiological exams and treatment of
those three pathologies are resumed here.
Acute quadriceps
tendon ruptures
Anamnesis and incidence
Acute quadriceps tendon ruptures are usually
found in patients over 40 years-old. The typical
history is a knee injury that leads to a period of
reduced mobility. Tendon rupture occurs [3-4]
weeks later, following sudden eccentric
contraction of the quadriceps muscle, while
minimal trauma such as descending stairs or
stumbling over a pavement. The patient feels a
violent pain followed by a functional disability
of the lower limb. Systemic diseases which
weaken tendons as systemic erythematous
lupus must be looked for.
Unilateral ruptures are 15 to 20 times more
frequent than bilateral ruptures that are found
in patients with a systemic disease as gout,
systemic erythematous lupus, rheumatoid
arthritis,
primary
hypoparathyroidism,
tuberculosis, syphilis, and acute infection. The
male/female ratio is 6/1. Rupture can also be
iatrogenous after steroid injection or due to
anabolic steroids use in athletes [14].
Diagnosis
The clinical exam is crucial for diagnosis. The
patient is unable to achieve a complete active
extension of the knee [20]. In supine position,
he is unable to rise up the lower limb extended
or is unable to hold this position against gravity.
While sitting on the border of the exam table
(knee flexed at 90°) he is unable to achieve full
knee extension. If the retinacula are intact
(aponeurosis of vastus medialis and vastus
lateralis that insert on the patella), the patient is
able to slightly extend the knee, but not
Acute ruptures of extensor
mechanism
V.B. Duthon, P. Neyret, E. Servien