Traumatic rupture of the patellar tendon is the result of
severe overloading of the extensor mechanism of the knee in young, athletic
patients. In contrast, prior injection of steroids and a variety
of systemic diseases are associated with an increased tendency to
rupture with little or no trauma1,2.
The rarity of bilateral patellar tendon rupture and the symmetry
of the findings on physical examination may cause clinicians to
miss the diagnosis.
We report a case of spontaneous bilateral patellar tendon rupture
in a patient with systemic lupus erythematosus. The patient was
seen twice in the emergency department without the injury being
recognized. This case highlights the potential difficulties in diagnosing
atraumatic bilateral patellar tendon rupture.
A thirty-year-old woman with a sixteen-year history of systemic
lupus erythematosus and recently diagnosed fibromyalgia was brought
by ambulance to a local emergency department because of bilateral
knee pain and an inability to bear weight on either leg. She was
taking prednisone (20 mg/day) on an ongoing basis. She
described a sharp pain in the right knee while standing still, which
caused her to shift her weight to the left knee. She also reported
a twisting sensation in the left knee with subsequent pain, and
an inability to bear weight on either leg. Physical examination
showed a left knee effusion and an inability to extend either knee,
which the examining physician attributed to pain. Radiographs of
the left knee showed no fracture (Fig. 1). The patient was diagnosed as
having a knee sprain; she was treated with a knee immobilizer bilaterally
and was given crutches for walking.
Seven days later, the patient returned to the emergency department
because of continued inability to walk due to buckling of the knees.
Examination by another physician showed bilateral knee effusion.
The physician documented normal strength and range of motion in
both knees, although the patient reported an inability to extend
the knees during this examination. Radiographs were not repeated,
and the patient was again discharged with the diagnosis of a knee
sprain.
Twenty-five days after the initial injury, the patient presented to
a rheumatologist because of continuing inability to walk or to extend
the knees. Examination showed bilateral knee effusion, tenderness,
and absence of active knee extension. Magnetic resonance imaging
showed bilateral patellar tendon rupture.
The patient was referred to the orthopaedic department. She underwent
bilateral tendon repair thirty days following the initial presentation.
Intraoperatively, both tendons were noted to be ruptured in their
midsubstance, thin, and attenuated. The tendons were repaired with
number-5 Ethibond suture (Ethicon, Somerville, New Jersey) with
the technique described by Krackow et al.3.
Because of the atrophic and retracted nature of the tendons (which
presumably was due in part to the delay in the diagnosis) at the
time of surgery, gradual and prolonged physical therapy was required.
By four months, the patient was able to stand from a sitting position
and to climb stairs with use of handrails. The range of motion of
each knee was 0° to 100°.