Functional tests specific to PFPS should include weightbearing
stress with various knee-flexion angles because these
are common aggravating positions and require dynamic muscular
control. Post and Fulkerson8 found that 86% of patients
with patellofemoral pain have pain during stair climbing and
85% have pain with squatting. The increase in pain with these
activities is correlated with an increase in patellofemoral joint
reaction force.3,4,8,14 At present, no functional tests specific to
the patellofemoral joint have been reported in the literature.
We evaluated the following functional performance tests in
this study: anteromedial lunge, step-down, single-leg press, bilateral
squat, and balance and reach. The anteromedial lunge
is a multiplanar movement designed to challenge the lateral
patellofemoral articulation with the valgus stress placed on the
knee during the maneuver.15 Theoretically, as an individual
lunges and the center of gravity moves forward and across the
body, the pull of the quadriceps muscle causes compressive
loading of the lateral patellofemoral articulation, a common
site of patellofemoral symptoms. The step-down mimics the
function of stair descent, a common aggravating factor. The
load of the patellofemoral joint with stair descent has been
reported to be 3.5 times body weight.16 A single-leg press test
was chosen to stress the patellofemoral joint in a partial
weight-bearing mode. This test can be administered early in
rehabilitation when a full squat may be too aggravating. To
further challenge the patellofemoral joint, a second test is a
full weight-bearing bilateral squat. The joint reaction force of
a squat to 908 is approximately 7.5 times body weight.3 The
balance-and-reach test, described by Gray,15 specifically challenges
single-leg balance.
The primary purpose of our study was to determine the
intrarater reliability of 5 functional performance tests on patients
with PFPS. Secondary purposes were to determine limb
symmetry index (LSI) differences for involved and uninvolved
limbs and to assess the relationship between the 5 functional
tests and pain ratings.