Patellofemoral the tendons of the tensor fasciae latae (TFL)

instability is a broad term that includes general symptomatic instability,
patellar dislocation, and patellar subluxation.1,2 Patellofemoral instability is a
complex, disabling musculoskeletal condition.1,2 The estimated incidence of
patellofemoral dislocation or subluxation has been recorded 43 per 100,000
people.2,3 Patellofemoral dislocation or
subluxation is more prevalent in women than men with the highest incidence
occurring in women from age 10 to 17.2,4,5

            The etiology of patellofemoral
instability is multifactorial.1 The causes can be divided into
biomechanical impairments and soft tissue faults.1 The biomechanical impairments include
rotational defects such as femoral anteversion and external tibial torsion.1,3 Supplementary biomechanical
abnormalities include several at the knee: genu valgum, genu recurvatum,
trochlear groove deformities, patella alta, and lateral insertion of the
patellar tendon.1,3,5 A biomechanical component distal to
the patella that is a factor in patellar dislocation or subluxation is
excessive foot pronation.1

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Soft tissue defects occur in the
muscles and ligaments surrounding the patella. Hypotrophy of the vastus
medialis oblique (VMO) with hypertrophy of the vastus lateralis causes a muscle
imbalance leading to the patella to be pulled laterally.1,3,5 In addition to the VMO, the adductor
muscle group acts as a medial force. The patella loses a medial stabilizer when
the adductors are weak.3 On the lateral side, the iliotibial
band (IT band) is a thick fibrous band arising from the tendons of the tensor
fasciae latae (TFL) and the gluteus maximus traveling along the lateral aspect
of the thigh and inserts on the lateral epicondyle of the femur.(need to site some anatomy book) When the IT band is tight, it causes
the patella to track laterally, predisposing the patella to dislocate.3 All of these factors are potential
stress imbalances placed on the patella, increasing the risk of subluxation or

The trochlear groove provides a bony
contribution to patellar stability.3 The lateral trochlea is elevated
compared to the medial aspect to counterattack the lateral forces on the
patella. Lateral forces that pull on the patella are the tight IT band and
hypertrophied vastus lateralis. The patella remains stable in the trochlea from
20 to 60 degrees of knee flexion. From 0 to 20 degrees of knee
flexion, the patella relies on soft tissue to prevent lateral subluxation or
dislocation. The medial patellofemoral ligament (MPFL) is the main
ligament responsible for preventing lateral subluxation or dislocation during
this range. The MPFL provides 60% of the restraint to the lateral forces
pulling on the patella.3 Rupture of the MPFL can lead to
lateral patellar subluxation or dislocation.1,3 Stability of the patella relies on
static and dynamic stabilizers, osseous structure, and limb alignment.1,3,5

            After an
acute patellar dislocation or subluxation, the recurrence of experiencing
another instability episode ranges from 15-44%.5 From a primary patellar dislocation,
55% of patients do not return to sports.5 After a second patellar dislocation,
the chance of a third dislocation increases to 50%.2,4,5 Patients become symptomatic with
walking on uneven terrain, descending stairs, running, and changing direction.2 Patients with patellofemoral
instability become symptomatic with fast, multidirectional movements.2 Patellofemoral instability results in
decreased activity, pain, long-term risk of osteoarthritis (OA), and decreased
quality of life (QoL).6

are several treatment options for patellofemoral instability. Conservative
treatment consists of physical therapy with an emphasis on VMO, gluteus
maximus, gluteus medius, and gluteus minimus strengthening.5 Patellar taping or bracing may be
done for added stability.5 If one of the etiologies of the
dislocation is osseous abnormality or a rupture of the MPFL, surgical treatment
is recommended.5 Physical therapy is indicated after
the surgical intervention to reduce edema, increase range of motion (ROM), and increase
strength in the musculature surrounding the patella.3 Whether a surgical or conservative approach
is selected, the goal is to regain function. Within treatment, measuring the progress
of patients is critical.6–8

The use of standardized outcome
measures provides a baseline of the patient and quantifies the change in function
of the patient throughout physical therapy.8 Outcome measures is defined as a tool
that measures change over a period of time.8 Outcome measures are important for
understanding the effectiveness of interventions.6,8 Understanding the results
of the treatment for specific diseases or disorders will provide guidance for
future treatment options.6–8 Outcome measures can be completed by
the patient or completed by the clinician.6 Outcome measures can obtain objective
or subjective information. Patient-reported
outcome measures (PROM) allow the clinicians to understand the perspectives of
the patients in regard to their health, quality of life, and functional
capacity.6 PROMs provide additional information
which allows the clinician to understand the patient’s perspective in how the
disorder, disease, or injury is impacting their life.7 Also, PROMs give the patients a voice
on how they believe the treatment is working.7 Outcome measurement tools are
designed for a specific patient population.8 The reliability and validity of the
tools are diminished when used outside of the patient population.8

Patient-Reported Outcome

In the literature, the Kujala Anterior
Knee Pain Scale (AKPS) and the Lysholm Knee Scoring Scale are the most commonly
used in patients with patellofemoral instability.9 These tools were not specifically
designed for patients with patellofemoral instability.6,9 The AKPS was developed in 1993.6 The AKPS is a patient-reported
questionnaire designed for patients with patellofemoral pain. The constructs of
the questionnaire are subjective symptoms and functional limitations. The
questionnaire examines difficulties with weight bearing, presence of a limp,
daily pain, pain with prolonged sitting in knee flexion, edema, weakness of
quadriceps, and decrease in flexion ROM of the knee. Limitations in walking,
climbing stairs, running, jumping, and squatting are examined. One question
examines perceived patellar instability.6 The scoring is hierarchical with a Likert
scale ranging from ‘unable – no difficulty’ and ‘severe pain – no pain.’ The total
score is out of 100.6,9 A lower score represents a higher
degree of disability. The AKPS is free and requires no training. The AKPS is easy
to understand and requires a short amount of time to complete.6,9

The Lysholm Knee Scoring Scale was
originally developed in 1982 for patients with knee ligamentous injuries.9,10 In 1985, a revised version of the
Lysholm was published.10 The Lysholm is an eight-question multiple
choice assessment that is filled out by the patient.9 The questionnaire examines degree of
limp, assistive devices, “locking” sensation, “giving away” sensation, intensity
of pain and swelling, and ability to climb stairs and squat.9,10 Each answer has an assigned amount of
points and are added to the total score. The highest score is 100. A higher
score indicates a higher degree of disability. The Lysholm is free and does not
require training. The Lysholm is easy to understand and easy to score.9,10 Both the Lysholm and the AKPS are
reliable and valid measurement tools.9 However, the tools were not designed
for patients with patellofemoral instability.6,9,10

In recent years, two PROMs have been
developed for patients with patellofemoral instability.2,6,11,12 The Norwich Patellar Instability
Score (NPI) was developed in March 2013 for patients with patellar instability.6 The NPI was developed by 90 patients
that were referred after experiencing patellar instability following a
dislocation.2 The participants were instructed to
rate their perceived level of instability during 19 activities. The activities
consisted of activities of daily living and sport activities. The 90 patients
assisted in weighting the activities. If patients frequently experienced
symptoms during an activity, then the task was weighted lower with less points.

If fewer patients experienced instability during the task, then the task was
weighted higher with more points. The aim was to rank activities according to
their severity. The questionnaire uses a Likert scale with 250 as the highest
possible points. The questionnaire is examining which functional activities
provoke patellar instability.2 Although it is patient specific, the
activities are more advanced and therefore could not apply to all patients with
patellofemoral instability. 2,6

The Banff Patellar Instability
Instrument (BPII) was published in July 2013.6,11 The BPII is also disease-specific for
patellar instability. There are 32 questions split into five sections: social
and emotional, lifestyle, sport and recreational, work concerns, and symptoms. The
BPII uses a holistic approach. The questionnaire examines the effects of the
patient’s patellar instability on their QoL. For each item, a 100 mm visual
analogue scale is provided. For each question, the patient marks an “x” on the
line. All the scores are added and converted to a score out of 100. A lower
score indicates greater disability. This instrument is free of charge and
requires no training.6,11

Clinimetric Properties

guidance from the COSMIN checklist, the clinimetric properties explored in this
paper are validity, reliability, responsiveness, and feasibility.6 Validity is defined as the instruments
ability to accurately measure what it is intended to.13 The definition of reliability is the
ability of the instrument to be consistent. The instrument should produce
consistent results for the same patient on different occasions if they exhibit
no change. Responsiveness is the sensitivity of the measurement to detect
change over a period of time.13 Feasibility includes the cost,
training required, length of time to administer, and the health literacy level
of the instrument. 1,2,6,12

Description of the patient

            A 19-year-old patient presented to
outpatient physical therapy following right knee MPFL reconstruction and
anteromedialization of tibial tubercle (AMZ) in May 2017. The patient has a
past medical history (PMH) of a chromosomal 2 abnormality, asthma,
ventriculoperitoneal shunt, and left patellar instability. The patient wears a
patellar stabilization brace on the left lower extremity (L LE). The patient
presented with patellar instability on the right side with multiple
dislocations, leading to the MPFL reconstruction and AMZ. Patient ambulated
with crutches for 12 weeks after surgery with a knee immobilizer that was
removed at 16 weeks.

patient is not in any pain, rating his pain 0 out of 10 on the virtual analogue
scale (VAS). The patient demonstrates full ROM in the right knee. The patient’s
manual muscle test (MMT) of bilateral lower extremity (B LE) muscles was 4/5. The
patient demonstrates slight weakness in right quadriceps with a grade of 3+/5.

The patient is unable to perform a single straight leg raise into flexion.

Interventions such as neuromuscular electrical stimulation (NMES) combined with
closed kinetic chain, open kinetic chain, and isometric exercises have failed
to strengthen the patient’s right quadriceps.

patient has several functional limitations. In gait, the patient lacks bilateral
knee extension and bilateral decreased step length. The patient is unable to
perform an eccentric contraction of the right quadriceps. The patient cannot
descend stairs in a reciprocal pattern, he must always lead with his R leg. The
patient is unable to complete high-level activities such as running or plyometrics.

The patient is motivated to get back to running and jumping. The patient is
also motivated to get back to his job at a daycare and as a high school football

Clinical question

            The patient is progressing according
to protocol. It is not unusual for patients to demonstrate quadriceps weakness
and to not be able to perform a single straight leg raise into flexion
following AMZ and MPFL reconstruction.3 The patient is still limited in
functional activities like descending stairs, running, and jumping. Once the
patient is able to perform these activities, the therapist should understand
how the patient perceives his symptoms of instability are impacting his
function.  We decided an important
question for our patient is which patient reported questionnaire is the most
accurate and reflective of change in function in adults with patellar
instability? For the purpose of the paper, we adapted the definition of
patellar instability to patients who have a medical diagnosis by magnetic
resonance imaging (MRI) or clinical examination of patellar dislocation,
subluxation, or general patellar laxity within the past two years. This
question focuses on determining the most effective PROM for patients with
patellar instability who are experiencing functional limitations due to
symptoms of instability.