Tj. Manal et L. Snyder-mackler, Failure of voluntary activation of the quadriceps femoris muscle after patellar contusion, J ORTHOP SP, 30(11), 2000, pp. 654-660
Study Design: Descriptive study of phenomenon.
Objectives: To determine the extent of failure of voluntary activation of t
he quadriceps femoris muscle in patients early after patellar confusion.
Background: Pain and effusion are related to the presence of quadriceps inh
ibition. We hypothesized that patients with patellar contusions would be un
able to fully recruit their quadriceps muscles and that the activation defi
cit would be associated with self-repel? measures of function.
Methods and Measures: Sixteen patients who had sustained a unilateral patel
lar contusion fewer than 4 months prior to testing participated in the stud
y (7 men, 9 women; mean age = 30.0 +/- 11.6). Subjects completed a self-rep
ort questionnaire to assess knee function and performed an isometric burst
superimposition test on the involved and uninvolved quadriceps at 60 degree
s of knee flexion. The subjects were assigned to 2 groups according to the
presence (n = 5) or absence (n = 11) of quadriceps inhibition.
Results: Sixty-nine percent of the subjects tested were able to fully activ
ate their quadriceps. Both groups had a decreased knee extensor force on th
e involved side compared to the uninvolved, but the group with inhibition h
ad a lower side-to-side percentage of knee extensor force (mean = 65.5% +/-
18.9) than those without inhibition (mean = 85.5% +/- 16.4).
Conclusion: Early after patellar contusion, approximately one-third of the
patients demonstrated quadriceps inhibition. According to our working hypot
hesis, the majority of the patients tested should have demonstrated inhibit
ion. Quadriceps inhibition was not associated with the activities of daily
living, sports activity, or global rating scales n this study. Decreased vo
litional quadriceps force production (the hallmark of inhibition) was the o
nly variable that discriminated patients with patellar contusion who had in
hibition from those who did not.