DISRUPTION OF QUADRICEPS FEMORIS
TENDON OR PATELLAR LIGAMENT
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| REPAIR OF EXTENSOR MECHANISM |
Damage to the quadriceps mechanism generally occurs when there is active contraction of the quadriceps femoris muscle against forced flexion of the knee. Most ruptures of this extensor mechanism occur in older patients. At the time of injury, the patient experiences sudden pain, which may be associated with a tearing sensation about the knee. The tendon may be weakened by age-related degenerative changes or by pathologic changes due to psoriatic arthritis, rheumatoid arthritis, arteriosclerosis, gout, hyperparathyroidism, diabetes, chronic renal failure, or corticosteroid therapy.
Physical Examination. Palpation of
the knee often reveals a hematoma, which may make examination difficult. A
high-riding patella may indicate rupture of the patellar ligament, whereas a
patella that is riding lower than normal suggests a rupture of the quadriceps
femoris tendon. A large defect may be palpable soon after injury, although if
the ruptured ligament is not treated for weeks or months the sulcus may fill
with scar tissue.
The most important finding during examination is the
patient’s inability to actively extend the knee fully against gravity. Also,
the patient may not be able to maintain a passively extended knee against
gravity. Patients with rupture of the quadriceps femoris tendon or patellar
ligament without involvement of the medial or lateral retinaculum may be able
to extend the injured knee actively to within 10 degrees of full extension.
When there is a widely separated tear of either tendon or ligament combined
with involvement of the medial and lateral retinacula, active extension is very
difficult. Patients with chronic rupture of the quadriceps femoris tendon
complain of giving way of the knee and marked weakness on attempting active
extension.
Imaging. Whereas
physical examination is often sufficient to diagnose disruptions of the
extensor mechanism, it is recommended to obtain plain radiographs to assess for
fracture and patellar positioning. MRI may be performed to assess the involved
soft tissues in detail, although this is not often necessary for these
patients. Treatment. Rupture of the quadriceps femoris tendon
generally occurs at its point of intersection into the superior pole of the
patella, whereas rupture of the patellar ligament usually occurs at the
inferior pole of the patella. In both cases, surgery is required to reestablish
the continuity of the quadriceps mechanism. The tendon or ligament most often
is reattached with sutures through drill holes in the patella. Then, the medial
and lateral retinacula are sutured. After surgery, the knee is routinely
immobilized in full extension for 6 to 8 weeks.
Patients who also have chronic metabolic disorders or
receive long-term corticosteroid treatment may require a more complex repair
that uses tendon, fascia, or wire to
reinforce the damaged quadriceps mechanism. After postoperative immobilization
for 8 to 10 weeks, patients gradually start protected range-of-motion exercises
and should use a cane or walker for some time.
Rupture of the patellar ligament may also occur at its insertion on the tibia, with or without fracture of the tibial tuberosity. In children whose growth plates have not yet closed, the ligament should be sutured, because this injury may disturb the growth of the proximal tibia. In adults, avulsion of the ligament from the tibial tuberosity is repaired by suturing the avulsed ligament though drill holes in the tibia or securing it with a metal staple or screw. A displaced fracture of the tibial tuberosity may be treated with open reduction and fixation with a metal screw.
