Orthopaedic Surgery - Patellofemoral Syndrome

Basics

Patellofemoral pain syndrome is a common disorder of the patellofemoral joint characterized primarily by:

Anterior or peripatellar knee pain.

Symptoms usually develop:

Gradually

rather than following a single major traumatic event.

Pain is typically aggravated by activities that place repetitive or sustained load on the patellofemoral articulation, particularly when the knee is flexed.

Typical Aggravating Activities

Symptoms commonly worsen with:

Running

Squatting

Lunging

Stair climbing

Jumping

Prolonged sitting with the knee flexed

Prevention

Prevention focuses on avoiding sudden increases in patellofemoral loading and correcting modifiable biomechanical factors.

Helpful measures include:

Gradual progression of training volume

Quadriceps strengthening

Hip abductor and external-rotator strengthening

Hamstring flexibility

Quadriceps flexibility

Calf and Achilles stretching

Appropriate recovery between training sessions

Exercises that reproduce substantial pain should be modified rather than universally prohibited.

Epidemiology

Patellofemoral pain is common in:

Adolescents

Young adults

Athletes

Runners

It is frequently reported more often in:

Females

than males.

Runners

Patellofemoral pain is one of the most common causes of knee pain in:

Recreational and competitive runners.

Older studies have reported very high incidence rates among amateur runners, although estimates vary substantially according to study population and diagnostic criteria.

Adolescents

Among adolescent amateur athletes, historical seasonal incidence has been reported at approximately:

5–15%.

Prevalence

Patellofemoral pain is common in the general population.

Older studies have reported annual prevalence estimates around:

20–25% in the general population

and close to:

30% in adolescents.

Exact prevalence depends on age, activity level, and diagnostic definition.

Risk Factors

Potential contributing factors include:

Female sex

Quadriceps weakness

Hip abductor or external-rotator weakness

Poor dynamic lower-extremity control

Hamstring tightness

Quadriceps tightness

Iliotibial band tightness

Heel-cord tightness

Patella alta

Rotational or coronal malalignment

Foot pronation

Extensor Mechanism Alignment

Structural factors that may influence patellofemoral mechanics include:

Increased femoral anteversion

Increased Q angle

Genu valgum

Genu varum

External tibial torsion

Pronated feet

Not every patient with these anatomic features develops symptoms, so examination findings should be interpreted together with functional mechanics.

Q Angle

The Q angle is formed by the intersection of:

A line from the anterior superior iliac spine to the center of the patella

and

A line from the center of the patella to the tibial tubercle.

A larger Q angle may increase the lateral vector acting on the patella, although Q angle alone is not sufficient to diagnose patellofemoral pain.

Genetics

There is no established inheritance pattern for patellofemoral pain syndrome.

Inherited skeletal alignment or connective-tissue characteristics may indirectly influence susceptibility in some individuals.

Pathophysiology

Patellofemoral pain is usually multifactorial.

It may result from a combination of:

Abnormal patellar tracking

Muscular weakness or imbalance

Reduced flexibility

Lower-extremity malalignment

Training overload

Excessive repetitive patellofemoral loading

Dynamic Malalignment

Poor control of the hip and lower extremity during weight-bearing activities may produce excessive:

Femoral internal rotation

Hip adduction

Dynamic knee valgus

These movements can increase patellofemoral joint stress even when static alignment is relatively normal.

Etiology

Potential contributing mechanisms include:

Extensor mechanism malalignment

Quadriceps weakness or imbalance

Hip muscle weakness

Retinacular tightness

Overuse

Abrupt increase in training intensity

Associated Conditions

Patellofemoral pain may coexist with:

Quadriceps weakness

Patellar maltracking

Patella alta

Patellar instability

Chondral abnormalities

Diagnosis

Patellofemoral pain syndrome is primarily a:

Clinical diagnosis.

Imaging is used when symptoms are atypical, persistent, or when another structural disorder is suspected.

Signs and Symptoms

The characteristic complaint is:

Anterior knee pain associated with loading of the flexed knee.

History

Pain commonly occurs during:

Stair climbing

Running

Squatting

Lunging

Jumping

Theater Sign

Patients may experience pain after prolonged sitting with the knee flexed, classically called the:

Theater sign.

The patient may feel the need to:

Straighten or move the knee

to reduce discomfort.

Pseudo-Giving Way

Some patients report that the knee:

Buckles or gives way.

This may result from:

Pain-related quadriceps inhibition

rather than true ligamentous instability.

True patellar instability or ligament injury should therefore be excluded.

Physical Examination

The examination should assess:

Patellar tracking

Lower-extremity alignment

Muscle strength

Flexibility

Patellar stability

Extensor Mechanism Alignment

Evaluate:

Q angle

Femoral rotation

Tibial torsion

Foot posture

Patellar height

Patellar Tracking

Observe the patella during:

Active knee flexion and extension.

Abnormal lateral tracking or a J-sign may suggest:

Patellofemoral maltracking or instability.

Retinacular Tenderness

Tenderness may be present along the:

Medial

or

Lateral patellar retinaculum.

Patellar Apprehension

Patellar instability should be assessed separately.

Lateral translation of the patella that produces:

Fear, guarding, or a sensation of impending dislocation

suggests a positive:

Patellar apprehension test.

This points toward instability rather than isolated patellofemoral pain syndrome.

Flexibility

Assess for tightness of the:

Quadriceps

Hamstrings

Iliotibial band

Gastrocnemius-Achilles complex

Strength

Evaluate:

Quadriceps strength

Hip abductors

Hip external rotators

Core control

Weakness in these areas may contribute to poor dynamic lower-extremity alignment.

Effusion

A large joint effusion is:

Not typical of uncomplicated patellofemoral pain syndrome.

A substantial effusion should prompt evaluation for another intra-articular disorder.

Patellar Loading

Compression or loading of the patellofemoral joint may reproduce:

Anterior knee pain.

However, isolated provocative tests have limited specificity and should be interpreted in the context of the overall examination.

Functional Examination

Observe:

Single-leg squat

Step-down

Running or landing mechanics when appropriate

Look for:

Dynamic valgus

Poor hip control

Pain reproduction

Imaging

Plain Radiographs

Radiographs are not mandatory in every uncomplicated case but may be obtained when symptoms are persistent, severe, atypical, or associated with suspected structural abnormality.

Typical views include:

AP

Lateral

Axial or Merchant view

Lateral View

The lateral radiograph can assess:

Patellar height

including possible:

Patella alta.

Merchant View

A Merchant view is a standardized tangential view of the patellofemoral joint, commonly obtained with approximately:

30° of knee flexion.

It can evaluate:

Patellar tilt

Patellar translation

Trochlear morphology

Sunrise View

A sunrise view generally requires greater knee flexion, often around:

45° or more.

It may be useful for assessing patellofemoral alignment but can underestimate subtle instability that occurs closer to extension.

MRI

MRI is not routinely required initially.

It may be useful in patients with:

Persistent symptoms despite prolonged rehabilitation

Mechanical symptoms

Large effusion

Suspected cartilage injury

Possible osteochondral lesion

Concern for alternative intra-articular pathology

Arthroscopy

Arthroscopy may demonstrate:

Patellar maltracking

or

Chondral degeneration

but it is not generally used solely to diagnose uncomplicated patellofemoral pain.

Pathological Findings

Some patients demonstrate:

Patellar malalignment

Cartilage softening or degeneration

Chondromalacia patellae

However, cartilage abnormalities do not always correlate directly with symptoms.

Chondromalacia

Chondromalacia refers specifically to:

Softening or degeneration of the articular cartilage of the patella.

It should not be considered synonymous with all patellofemoral pain.

Differential Diagnosis

Important alternative diagnoses include:

Quadriceps tendinopathy

Patellar tendinopathy

Patellofemoral osteoarthritis

Osteochondritis dissecans

Synovial plica syndrome

Patellar instability

Meniscal injury

Osteochondral injury

Treatment

Initial Management

The initial goals are to:

Reduce pain

Modify aggravating activity

Restore flexibility

Improve muscular control

Gradually return to activity

Symptom Control

During an acute exacerbation, treatment may include:

Ice

Short-term NSAIDs when appropriate

Activity modification

Exercise

Early exercise may include:

Quadriceps activation

Hip and core strengthening

Gentle stretching

The exercise program should be adjusted so that loading is:

Tolerable and progressively increased.

General Measures

The mainstay of treatment is:

Nonoperative rehabilitation.

Most patients improve with a structured program combining:

Physical therapy

Activity modification

Progressive strengthening

Flexibility training

Activity Modification

Temporarily reduce activities that markedly reproduce symptoms, such as:

Deep squatting

High-volume stairs

Steep uphill running

Repeated jumping

High-load knee extension exercises

These activities may later be reintroduced gradually as strength and tolerance improve.

Open-Chain Exercise

Older treatment protocols often recommended avoiding open-chain quadriceps exercises entirely.

Current rehabilitation typically uses both:

Open-chain

and

Closed-chain

strengthening when appropriately dosed.

The important consideration is avoiding excessive patellofemoral loading within painful ranges.

Training Progression

Sudden increases in:

Mileage

Intensity

Hill work

Jump volume

should be avoided.

A graded return to training reduces recurrence risk.

Stretching

Stretching may target:

Quadriceps

Hamstrings

Calf-Achilles complex

Iliotibial band when clinically restricted

Patellar Taping

Patellar taping may provide:

Short-term pain reduction

in some patients.

It is best used as an adjunct to:

Exercise-based rehabilitation, rather than as a stand-alone treatment.

Bracing

A patellofemoral brace may help selected patients by:

Improving comfort

Providing proprioceptive feedback

Supporting patellar tracking

Results vary between patients.

Foot Orthoses

Foot orthoses may be useful in selected patients with:

Excessive pronation or altered foot mechanics.

They may improve symptoms when combined with exercise therapy.

Electrical Stimulation

Neuromuscular electrical stimulation may supplement therapy in patients with:

Difficulty activating the quadriceps, although it is not routinely necessary.

Physical Therapy

Physical therapy is the primary treatment modality.

A comprehensive program should include:

Quadriceps strengthening

Hip abductor strengthening

Hip external-rotator strengthening

Core stabilization

Functional movement retraining

Hamstring flexibility

Quadriceps flexibility

Calf flexibility

Eccentric Strengthening

Eccentric and controlled loading exercises may improve:

Quadriceps capacity

Patellar load tolerance

Functional control.

Dynamic Stability

Rehabilitation should address:

Single-leg control

Landing mechanics

Running mechanics

Dynamic valgus

Medication

NSAIDs may be used orally or topically for:

Short-term pain relief, when appropriate.

They do not correct the underlying biomechanical contributors.

Surgery

Surgery is:

Rarely required.

It should be considered only after a:

Well-documented, prolonged course of appropriate nonoperative treatment, often at least several months.

Surgical Indications

Surgery should generally be reserved for patients with:

A specific structural abnormality

or

A focal mechanical lesion clearly responsible for symptoms.

Nonspecific anterior knee pain alone is not an indication for surgery.

Chondroplasty

Arthroscopic chondroplasty may be considered when there are:

Unstable cartilage flaps

or

Mechanical symptoms from a discrete chondral lesion.

It is not routinely performed for uncomplicated patellofemoral pain.

Lateral Release

Lateral release is rarely indicated.

It may be considered only when there is:

Documented pathological lateral retinacular tightness or lateral patellar compression.

It should not be performed routinely for patellofemoral pain or instability.

Medial Instability

An overly aggressive lateral release may produce:

Iatrogenic medial patellar instability.

This can be difficult to treat and must be avoided.

Follow-Up

Early follow-up focuses on:

Quadriceps activation

Pain reduction

Restoration of motion

Correction of functional deficits

Referral

Early specialist evaluation is appropriate when anterior knee pain is associated with:

True patellar instability

Recurrent dislocation

Large or recurrent effusions

Mechanical locking

Suspected osteochondral injury

Failure of structured rehabilitation

Prognosis

Most patients improve with:

Physical therapy

Activity modification

Progressive strengthening

Correction of contributing biomechanical factors

Recovery may take:

Several weeks to several months, particularly when symptoms have been present for a long time.

Persistent Symptoms

Patients who fail to improve should be reassessed for:

Patellar instability

Cartilage injury

Tendon pathology

Osteochondral disease

Incorrect initial diagnosis

Surgical Prognosis

When surgery is performed for a clearly identified and correctable mechanical abnormality, outcomes are generally better than when surgery is performed for nonspecific anterior knee pain.

Key Principle

Patellofemoral pain syndrome is a multifactorial cause of anterior knee pain related to patellofemoral loading, muscular control, alignment, and activity level.

The cornerstone of treatment is:

Progressive exercise-based rehabilitation emphasizing quadriceps, hip, and core strength together with flexibility and activity modification.

Most patients improve without surgery.