CHAPTER 58 • KNEE MENISCAL INJURIES 345- Removal of a portion of the meniscus results in a
decreased contact area between the femur and tibia.
Medial meniscectomy decreases the contact area by
up to 70%. - Resection of as little as 15–34% of the meniscus
results in increased contact pressure by up to 350%
(Simon et al, 2000).
EPIDEMIOLOGY
- The annual incidence of meniscal injury is 60–70 per
100,000 persons (Greis et al, 2002a). - Meniscus injury is more common in males, with a
male to female ratio between 2.5:1 and 4:1 (Greis
et al, 2002a). - Approximately one-third of all tears are associated
with ACL injury, and approximately 80% of repairable
meniscal tears occur during ACL injury (Klimkiewicz
and Shaffer, 2002). - Meniscal tears are also commonly associated with
tibia plateau fractures, and femoral shaft fractures.
•Degenerative tears in men peak in the 4th through 6th
decade, and in women remain relatively constant after
the second decade (Greis et al, 2002a). - Medial meniscus tears are more common than lateral,
and tears are most frequently located in the midpor-
tion and posterior horns of the meniscus. - Medial meniscal tears are more commonly longitudi-
nal type, whereas laterally a radial component is more
frequent (Klimkiewicz and Shaffer, 2002).
DIAGNOSIS OF MENISCAL INJURY
HISTORY
- Meniscal injury during sport occurs most frequently
during noncontact cutting, deceleration, hyperflexion,
or landing from a jump.
•Degenerative meniscal injury with aging (>40 years)
often occurs after trivial insult. The tear may not be
noticed at the time of injury. The mechanical symp-
toms that follow often trigger the patient to seek atten-
tion. - Mechanical symptoms of popping, catching, locking,
or buckling, along with joint line pain are suggestive
of meniscal tear. These are nonspecific symptoms,
and may be secondary to chondral injury, or
patellofemoral chondrosis (Greis et al, 2002a). - Mild synovitis often results from the injury, with
swelling present for several days following the
event. The synovitis may be recurrent and activity
related.- An audible pop at the time of injury is more charac-
teristic of an ACL tear; however, a meniscus tear is
commonly present in this scenario. - Immediate swelling suggests bleeding, and is frequently
not present after isolated meniscus tear; however, may
be present with a more peripherally based tear.
•A delayed effusion is more characteristic of meniscus
injury, with the production of reactive joint fluid. - The reporting of loss of motion with a sensation of a
mechanical block to extension is suggestive of a dis-
placed meniscus tear (Greis et al, 2002a).
•A history of a snapping or popping knee may suggest
a discoid variant. Mechanical symptoms present in
childhood or adolescence, without a history of
trauma, should raise the suspicion of the presence of a
discoid meniscus (Rath and Richmond, 2000). - The complete history should include assessment of
the patient’s lifestyle, activity level, occupation, and
medical history. Younger, more active individuals
often require more aggressive management.
- An audible pop at the time of injury is more charac-
PHYSICAL EXAMINATION- Examination begins with evaluation of gait. A limp is
common after meniscus tear, and pain after an acute
injury may result in the inability to bear weight. - Inspection of the knee includes evaluation for an effu-
sion, as well as thigh asymmetry in the setting of a
chronic tear. - Range of motion is assessed in comparison to the
opposite extremity. A displaced tear may block the
knee from achieving full extension, as well as impair
flexion. A mechanical block to motion is termed the
locked knee.
•Palpation of the joint lines is performed in an effort to
elicit tenderness, and may be the best clinical sign of
a tear, with 74% sensitivity, and 50% positive predic-
tive value (Greis et al, 2002a).
•Pain at terminal flexion or extension may be present,
depending on the location of the tear. - The McMurray test is performed with the patient
supine. The hip and knee are flexed, and the foot is
alternately internally and externally rotated during
application of a circumduction maneuver to the knee.
Concurrently, the examiner palpates the posterolateral
and posteromedial joint lines. - Medial meniscal injury is tested by extending the knee
with the foot externally rotated. Lateral meniscal
injury is assessed with the foot internally rotated.
•A palpable and audible clunk is considered a positive
McMurray test. A true positive test is uncommon, even
in the presence of a tear, but is nearly 100% specific.
The sensitivity of the test is as low as 15% (Greis et al,