Date of Paper/Work
Type of Paper/Work
Doctor of Physical Therapy (DPT)
Background: Much of the current literature around risk factors for patellar
instability directs attention to anatomical/structural features such as femoral
antero-version, patellar alignment, Q-angle, and MPFL disruption. There is
limited research indicating clinically relevant tests to identify functional and
strength-associated risk factors for patients with patellar instability.
Purpose: To determine reliability and validity of lower extremity functional tests
applicable to patients with patellofemoral instability in a healthy control group.
Methods: Twenty-four healthy subjects underwent hip strength, endurance, and
lower extremity functional tests on their dominant and non-dominant lower
extremities. Hip abduction, extension, and external rotation strength were
assessed with hand-held dynamometry utilizing reinforcing straps. Functional
endurance tests were assessed bilaterally. Functional assessments were
videotaped and assessed at a later date. Each subject completed the
International Physical Activity Questionnaire (IPAQ) to determine his or her
weekly activity levels. Independent t-tests were used to assess differences
between subjects who tested positive versus negative on the functional tests.
Inter-rater reliability for functional tests was assessed using kappa and Pearson
correlations were used to assess relationships among the strength, endurance,
and functional tests.
Results: Inter-rater reliability for the single leg squat and step down test was
determined to have fair-moderate agreement among 5 raters. The side plank
endurance test was significantly lower for subjects who were positive for knee
medial to toe on the single leg squat test. Low correlations were found between
hip strength and functional endurance testing. Scores on the IPAQ had moderate
correlation with the side plank.
Conclusions: Single leg squat showed adequate reliability and demonstrated
good construct validity with the lateral plank endurance test. The low correlation
between hip strength and functional endurance suggests that these
measurements identify different aspects of muscle function in healthy controls.
Given these findings, it is recommended that clinicians utilize both strength
measurements and endurance tests along with lower extremity functional testing
in the assessment of individuals with lower extremity dysfunction. Further testing
is needed in a patient population with patellofemoral instability.
Alschlager, Samantha; Honnette, Danielle; Ley, Katelyn; Ludtke, Brianna; and Reed, Kristen, "Proximal Strength and Functional Testing Applicable to Patellofemoral Instability: A Preliminary Study" (2015). Doctor of Physical Therapy Research Papers. 38.