Functional performance tests that are specific for PFPS
should be chosen based on clinical evidence and the ease of
replication among clinics and facilities. Pain is a factor associated
with PFPS and is commonly used as a measurement to
determine functional improvement. Chesworth et al13 evaluated
the visual analog scale (a measure of pain) in patients
with PFPS, finding poor day-to-day reliability but good sensitivity
to clinical changes. In addition to measuring pain directly,
performance of a functional test may add information
regarding muscle strength, endurance, proprioception, and balance.