Understanding Red Flags in Patellofemoral Pain

Original Editor - Carin Hunter based on the course by Claire Robertson
Top Contributors - Carin Hunter, Jess Bell and Kim Jackson

Introduction

Screening for red flags is an important part of the assessment process, but it is often overlooked in patients with knee pain. It is important to have a good understanding of red flags for patient safety and to ensure appropriate and timely referrals are made when necessary. If there has been any trauma to the knee, it is necessary to make sure that all relevant investigations have been carried out. For more information on red flags, please see this page: An Introduction to Red Flags in Serious Pathology.

Non-Traumatic Masquerading Conditions

There are certain conditions that can have similar pain patterns as patellofemoral pain, and these should be considered in a differential diagnosis. The following non-traumatic conditions occur in the adolescent population (i.e. pre-teen and teen).

Osgood-Schlatter Disease (OSD)

Signs and Symptoms:

• This condition is common in adolescents aged 11-15 years old
• It is prevalent in children participating in quadriceps dominant sports, i.e. running, kicking and jumping
• Patients present with an obvious bump at the tibial tubercle
• Pain is specific to the tibial tubercle
• Inflammation and elevation of the growth plates are present in the tibial tuberosity
• An MRI to show the level of inflammation can be used as confirmation, but this will not change the treatment plan
• Pain can progress to a level that prevents any participation in sport if left untreated

Treatment:

• Education
• Activity modification:
  • Try to eliminate the patient's least favourite sport, or
  • Change their playing position to a less active position to decrease load
• NSAIDS (non-steroidal anti-inflammatories)
• Ice massage - this will provide symptomatic relief
• Address overload:
  • Extrinsic factors
    • Load management of sport
    • Footwear
    • Landing technique
  • Intrinsic factors
    • Muscle length
    • Muscle strength

For more information, please see Osgood-Schlatter Disease.

Sinding Larsen Johansson Syndrome

Sinding Larsen Johansson Syndrome (SLJS) is a juvenile osteochondrosis and traction epiphysitis. It affects the extensor mechanism of the knee, which disturbs the patella tendon attachment to the inferior pole of the patella. There is tenderness of the inferior pole of the patella. This is usually accompanied by x-ray evidence of splintering of that pole. Most patients with SLJS also have calcification at the inferior pole of the patella.

The syndrome usually appears in adolescence, during a growth spurt. It is associated with localised pain which is worsened by exercise. Usually localised tenderness and soft tissue swelling are observed. The surrounding muscles may also be tight, particularly the quadriceps, hamstrings and gastrocnemius. This tightness usually results in inflexibility at the knee joint, which alters the stress applied through the patellofemoral joint.

Signs and Symptoms:

• Inflammation at the growth plate of the distal pole of the patella
• This condition is most likely to be seen during growth spurts
• Primary treatment focuses on tracking growth for activity modification during a growth spurt
• Pain can progress to a level that prevents any participation in sport

Treatment:

• Education
• Activity modification:
  • Try to eliminate the patient's least favourite sport, or
  • Change their playing position to a less active position to decrease load
• NSAIDS (non-steroidal anti-inflammatories)
• Ice massage - to provide symptomatic relief
• Address overload:
  • Extrinsic factors
    • Load management of sport
    • Footwear
    • Landing technique
  • Intrinsic factors
    • Muscle length
    • Muscle strength

For more information, please see Sinding-Larsen-Johansson Syndrome.

Knee Effusion

There are no instances where a child should have a knee effusion without a cause. Thus, any effusion in the absence of trauma should always be investigated. A knee effusion can often lead to patellofemoral pain.

Possible Effusion Causes:

• Systemic autoimmune disease (eg. juvenile arthritis)
• Infective arthritis
• Osteochondritis dissecans

Autoimmune Disease Red Flags:

• Multiple joint involvement
• Joint is stiff on waking
• Fatigue

Infective Arthritis Red Flags:

• Temperature
• Recent illness

Osteochondritis Dissecans/Osteochondral Defect

Osteochondritis dissecans (OCD) is defined as an inflammatory pathology of bone and cartilage. This can result in localised necrosis and fragmentation of bone and cartilage. Cartilage and subchondral bone can break off and float in the joint. This irritates the synovium, which causes an effusion.

Osteochondritis Dissecans Treatment:

• Manage conservatively for stable lesions
• Possible debridement / knee wash out
• Possible surgical resection (resect back to a stable margin)
• Review the osteochondral defects with an MRI - check for stability of the margins of the osteochondral defect and if the location is a weight-bearing zone
• Monitor bone oedema around a defect - the oedema should decrease when serially monitored
• Physiotherapy advice: load management
  • When there is a trochlear osteochondral defect in the patellofemoral joint, remember to avoid excessive deep loaded flexion

For more information, please see Osteochondritis Dissecans and Osteochondritis Dissecans of the Knee.

Slipped Capital Femoral Epiphysis

Slipped capital femoral epiphysis is not common. However, it needs to be considered as a differential diagnosis as it is can refer pain to the anteromedial knee. A mild condition diagnosed early has a better outcome as the condition will progress until the epiphysis is fused.

For more information, please see Slipped Capital Femoral Epiphysis.

Others

Less common but more serious:

• Systemic auto-immune disease
• Slipped epiphysis
• Femoroacetabular impingement (FAI)
• Leukaemia
• Metastatic neuroblastoma
• Primary bone tumour
• Red flags
  • Night pain
  • Weight loss
  • Malaise

Conditions That Can Occur in the Adult Population

The following conditions should be considered in the differential diagnosis of adults presenting with patellofemoral pain symptoms.

Posterior Cruciate Ligament Rupture

A rupture of the posterior cruciate ligament (PCL) can be caused by a blow to the front of the knee. For some patients, their only reported symptom is patellofemoral joint pain. It is, therefore, advisable to assess all ligaments to see if surgery is necessary. Physiotherapy for an injury to the PCL will often focus on quadriceps rehabilitation.

For more information, please see this page: PCL Reconstruction.

Synovial Plica

A plica is a fold in the synovial membrane. They are common and are normally asymptomatic. A plica can often be palpated anteromedially, next to the superior half of the patella. Occasionally, they can get trapped in the patellofemoral joint, and become impinged or inflamed and sore.

Diagnosis:

• Inject with local anaesthetic for symptomatic relief. If this is successful, it strongly indicates an inflamed synovial plica.

Treatment:

• Steroid injections to decrease inflammation
• Plica resection
• Rehabilitation

Patellar Tendinopathy

Tendinopathy is a failed healing response of the tendon, with haphazard proliferation of tenocytes, intracellular abnormalities in tenocytes, disruption of collagen fibres, and a subsequent increase in non-collagenous matrix.  The term tendinopathy is a generic descriptor of the clinical conditions (both pain and pathological characteristics) associated with overuse in and around tendons.

Treatment:

• Heavy resistance loading
• Eccentric decline loading

	Patellar Tendinopathy	Patellofemoral Pain
Aggravating Factors	Being still Early morning	Being still if knee at end of range flexion
Description of Pain	Pinpoint to proximal tendon	Vague
Effect of Excercise	Pain decreases as tendon warms up	Worsens with repetitive load

For more information, please see Patellar Tendinopathy.

Femoroacetabular Impingement

While femeroacetabular impingement (FAI) is not common, it can refer pain to the anteromedial knee. This referred pain could be confused with patellofemoral pain. One of the most commonly recognised clinical signs for FAI is pain with hip flexion, adduction, and internal rotation, so it can be useful to perform the Quadrant Test. In relation to patellofemoral pain, you will be looking to see if the patient's knee pain is reproduced on testing.

For more information, please see Femoroacetabular Impingement.

Assessment Tools

When encouraging an individual to modify their activity levels, it can be helpful to print out / provide a table for them to accurately track their volume of exercise in a week (see figure below). Be sure to encourage your client to fill out the form accurately as this will ensure you can offer the most relevant advice. It is also advisable to correctly record the length of time spent on each activity and the intensity of the activity.

Load Assessment Table for Growth Tracking.