Date of Paper/Work


Type of Paper/Work

Research Project

Degree Name

Doctor of Physical Therapy (DPT)


Physical Therapy

First Advisor

John Schmitt

Second Advisor

Kristen Gerlach


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.