PATELLOFEMORAL PAIN SYNDROME

QUESTIONS AND ANSWERS

Causes of PFPS

PFPS can develop from several factors, including overuse, improper kneecap alignment, muscle imbalances, and injury. Overuse is a common cause and occurs during activities that involve repetitive knee movements like running, jumping, or cycling. Improper kneecap alignment, called patellar malalignment, causes the patella to rub against the femur. This friction can lead to pain and discomfort in the front of the knee. Muscle imbalances—particularly weakness or tightness in the muscles surrounding the knee—can also contribute to PFPS.

Underlying Mechanisms and Contributing Factors

Several internal and external factors may raise the risk of PFPS:

Muscle Weakness and Imbalance:

Weak quadriceps, especially the vastus medialis oblique (VMO), can reduce patellar stability. Tightness in the vastus lateralis, IT band, or hamstrings may worsen patellar tracking. These imbalances place uneven pressure on the kneecap during movement, causing discomfort and pain.

Biomechanical Abnormalities:

Certain anatomical traits can change the way the kneecap tracks. An increased Q-angle, flat feet, or excessive rearfoot eversion are common contributors. These conditions raise lateral forces on the patella, increasing joint stress and worsening symptoms.

Hip and Core Weakness:

Weak gluteus medius and gluteus maximus muscles can increase hip adduction and internal rotation during activity. These changes raise the Q-angle and place extra strain on the knee joint.

Running Technique and Training Load:

Sudden increases in activity, downhill running, or uneven surfaces can overload the patellofemoral joint. This strain contributes to joint stress and may trigger symptoms of PFPS.

Dynamic Valgus:

Improper movement patterns, such as knees collapsing inward during squats or jumps, stress the kneecap and surrounding tissues. Tight Hamstrings:
Limited hamstring flexibility can change knee mechanics and increase joint pressure, contributing to PFPS.

Trauma or Injury:

A fall or a direct blow to the knee can also lead to the onset of PFPS. When injured, the forces acting on the kneecap may increase compression against the underlying bone. This is especially true along the patellar facets. Over time, this pressure may lead to joint irritation, instability, and pain. Malalignment may involve a lateral tilt or a superior shift of the patella. These changes often occur when the knee is fully extended or bearing weight. Research shows that individuals with PFPS typically have a greater patellar tilt and lateral shift than those without pain. Such alignment problems often stem from tightness in the hamstrings or the iliotibial band.

Imbalances in the quadriceps muscles also play a role. When these muscles are too tight or weak, they can pull the kneecap out of its proper path. This leads to pain, especially during movement. Although more research is needed, muscle strength and activation clearly affect PFPS development. Biomechanical factors are central to both the cause and persistence of this condition.

Additional Causes

Weak quadriceps—especially the vastus medialis—can significantly contribute to PFPS. Hip stabilizer weakness, particularly in the abductors and external rotators, may also change how the knee moves. Poor motor control at the ankle can further disrupt alignment and increase stress on the knee joint. A frequently discussed topic in research is the relationship between the vastus lateralis and the vastus medialis oblique (VMO).

Imbalances between these two muscles can cause abnormal patellar tracking. When the kneecap moves out of its groove, stress increases in the joint. This lateral stress contributes to the hallmark pain of PFPS. A direct blow or fall on the knee can also initiate PFPS.

Role of Alignment and Muscle Imbalance

Patellar alignment and tilt are important in PFPS development. Malalignment is often related to tight hamstrings, IT band issues, and quadriceps imbalances. When these supporting muscles are either tight or weak, kneecap tracking becomes abnormal. This increases pressure on the joint and can lead to pain during movement.

Traumatic injuries such as falls or direct hits can also trigger PFPS.

Biomechanical Factors and the Role of the Q-Angle

The quadriceps muscle, especially the vastus lateralis, can pull the patella laterally and slightly backward when it contracts. This pull is measured by the Q-angle, which involves two lines:

One line runs from the front of the hip to the center of the kneecap. The second line goes from the kneecap to the top of the shinbone. A normal Q-angle ranges from 13 to 15 degrees. An increased Q-angle places more lateral force on the patella. Extra tension in the IT band or lateral retinacular fibers can make this worse. These forces contribute to pain and improper kneecap tracking, hallmark features of PFPS.

Patellofemoral Pain Syndrome Symptoms

PFPS is typically characterized by pain and discomfort in the front of the knee, especially when bending the knee, climbing stairs, or sitting for long periods. Other symptoms may include swelling, popping or cracking sounds in the knee, and difficulty straightening the knee.

Recognizing Patterns of Pain

The nature and timing of pain can provide important clues:

• Pain only during activity: This may suggest issues with biomechanics—how the knee moves during motion. For example, running or jumping may trigger discomfort.
• Pain only after activity, especially much later or the next day: This pattern often points to inflammation in the joint or surrounding tissues.
• Pain that improves with exercise: In some cases, discomfort lessens as activity continues, which can indicate problems related to tendon or muscle flexibility.

Understanding when and how the pain occurs can help guide both diagnosis and treatment, as these patterns often reveal the underlying cause of PFPS.

Diagnosing PFPS

Diagnosing PFPS involves a thorough physical exam and review of the patient’s medical history. The physician looks for swelling, tenderness, and signs of misalignment in the kneecap. They may also assess the strength and flexibility of the surrounding muscles.

In addition to these assessments, the diagnosis of Patellofemoral Pain Syndrome (PFPS) is based on several criteria:

• Retropatellar or peripatellar pain: Pain is located behind or around the kneecap.

• Pain during specific activities: Discomfort worsens during activities that bend the knee under load, such as squatting, stair climbing, or prolonged sitting.

• Exclusion of other causes: Before confirming PFPS, doctors rule out other sources of anterior knee pain, such as tibiofemoral joint injuries or structural problems.

By combining history, physical examination, and key criteria, your doctor can distinguish PFPS from other knee conditions and recommend the best treatment.

Taking a careful history is crucial. The doctor will ask if symptoms developed gradually or followed an activity like long-distance running or climbing stairs. Pain that starts without trauma is more typical of PFPS. A direct injury may suggest another cause.

Common Symptom Patterns

The way knee pain appears can help identify contributing factors:

• Pain with activity: Discomfort during stairs, squatting, kneeling, or prolonged sitting (“theater sign”) often points to PFPS.

• Pain while sitting with knees bent: This may suggest tight quadriceps compressing the joint.

• Pain walking uphill or downhill: Uphill pain may suggest tight calves or weak glutes; downhill pain stresses the joint and the quadriceps.

• Pain from tight clothing: Jeans or garments pressing on the knee may increase compression.

• Timing of pain: Pain only during activity may suggest biomechanics, while pain after activity suggests inflammation.

By collecting these details and performing a physical exam, the physician can identify causes and develop a tailored treatment plan. During the interview, your doctor will ask when symptoms started, how long they last, and if any activities worsen the pain. Questions may also cover past injuries, activity level, daily habits, and prior treatments.

Combining history with physical findings allows for accurate diagnosis and exclusion of other knee issues. If left untreated, the condition can persist and become more difficult to manage, with some people continuing to experience symptoms years after diagnosis.

Key Diagnostic Signs

To confirm PFPS, doctors look for specific pain patterns:

• Pain with muscle contraction: Discomfort when tightening the quadriceps, such as when straightening the knee.

• Pain while squatting: Pain increases during the squat motion.

• Pain on palpation or kneeling: Tenderness around the kneecap or pain when kneeling.

A diagnosis is more likely if two of these three signs are present. When all three occur together, PFPS is strongly suspected. A combination of detailed history, physical assessment, and diagnostic criteria ensures an accurate diagnosis and a targeted treatment plan.

PFPS is typically characterized by pain and discomfort in the front of the knee, especially when bending the knee, climbing stairs, or sitting for long periods. Other symptoms may include swelling, popping or cracking sounds in the knee, and difficulty straightening the knee.
This pain is often brought on or worsened by activities that increase the load on the patellofemoral joint while the knee is flexed, such as running, going up or down stairs, squatting, or even sitting with bent knees for extended periods (sometimes called the “theater sign”).

Some individuals may notice crepitus, a grinding or crackling sensation, at the joint, as well as tenderness when pressing around the edges of the kneecap. Occasionally, a mild swelling (effusion) may develop. It’s important to recognize and address symptoms of PFPS early.

Attention is also given to the quadriceps muscles. Weakness in the vastus medialis oblique or tightness in the vastus lateralis can impact knee alignment and contribute to pain, so exercises may be tailored to address these specific muscle groups. Resting the knee and avoiding activities that aggravate the pain can also help alleviate symptoms. Doctors will also suggest pain management techniques, such as ice therapy and over-the-counter pain medications.

To complete the assessment, doctors often examine:

• Observation: The doctor checks the patella position, tilt, and movement. They also assess femur alignment and muscle bulk around the knee, including the gluteals, quadriceps, vasti, and calves. Swelling, inflammation, and foot position are also noted.

• Joint mobility: Doctors evaluate knee movement and check for loss of extension or excess joint laxity.

• Muscle activation and endurance: The physician observes how well the vastus medialis oblique (VMO) activates and its endurance at different flexion angles. They also assess gluteal function as hip abductors and rotators.

• Muscle length and flexibility: Tests such as the Modified Thomas test assess hip flexors, quadriceps, TFL, hamstrings, gastrocnemius, soleus, and gluteus maximus flexibility.

• Functional movements: Activities like one-leg standing, stair climbing, or walking are observed for control and compensation. Adjusting the patella, femur, or foot alignment during these movements may reveal pain sources.

• Gait assessment: The doctor watches for early heel rise, poor control of pelvis or femur, short stride, trunk leaning, or scissoring.

These combined observations help diagnose PFPS and reveal the biomechanical issues causing pain.

Long-term management

Management of PFPS goes beyond initial symptom relief, aiming to restore full function and help your child safely return to activity. Education plays a crucial role; children and families are taught how to recognize early symptoms and modify activities to prevent flare-ups. Gait retraining, often guided by physical therapists, helps correct any abnormal walking or running patterns that may contribute to pain. In some cases, foot orthoses (custom shoe inserts) can be recommended to address issues with foot alignment and relieve stress on the knee.

A comprehensive rehabilitation plan typically involves a combination of exercises, stretching, and, when appropriate, the use of supportive devices. This multimodal approach, incorporating education, exercise, gait correction, and orthotic support, has been shown to effectively reduce pain and improve function, allowing children to resume sports and regular activities.

In some cases, surgeons will also recommend surgery to correct the underlying issue causing PFPS. Surgery may involve realigning the kneecap or repairing damaged cartilage. However, doctors consider surgery for severe cases of PFPS that have not responded to non-surgical treatments.

In some cases, surgeons will also recommend surgery to correct the underlying issue causing PFPS. Surgery may involve realigning the kneecap or repairing damaged cartilage. However, doctors consider surgery for severe cases of PFPS that have not responded to non-surgical treatments.

Patellofemoral Pain Syndrome Preventive Measures

Prevention measures for PFPS involve maintaining proper form and technique during physical activity, wearing appropriate footwear, and incorporating strength and flexibility exercises into a regular exercise routine. It is also important to gradually increase the intensity and duration of physical activity to avoid overuse injuries.

In addition to these general guidelines, addressing factors beyond the knee itself can play a significant role in prevention. Sometimes, issues such as flat feet (pes planus) or high arches (pes cavus) can contribute to PFPS. For example, foot pronation—more common in those with PFPS—can cause internal rotation of the tibia or femur, disrupting the patellofemoral mechanism. On the other hand, foot supination may reduce the natural shock absorption during activities, placing extra stress on the knee.

Hip strength is another important consideration. Weakness in the hip abductor muscles can alter hip movement and increase strain on the knee, especially during activities like running. Incorporating exercises that target hip strength and addressing foot alignment with supportive footwear or orthotics, when appropriate, can further reduce the risk of developing PFPS.

A comprehensive Approach

By taking a comprehensive approach, including attention to lower limb alignment and muscle balance, individuals can help protect against patellofemoral pain and support long-term knee health. Along with these physical strategies, education plays a crucial role in both the prevention and management of PFPS. Ensuring that children, parents, and young athletes understand the symptoms of PFPS and how to manage training loads can make a significant difference. For example:

• Promote Awareness: Teach children and families to recognize early signs of knee pain so they can respond promptly.
• Set Realistic Expectations: Help young athletes understand what to expect during recovery and the importance of patience.
• Encourage Self-Management: Foster confidence in managing symptoms at home, including when to rest and how to modify activities if pain arises.
• Prioritize Adherence: Emphasize the importance of sticking with prescribed exercises and physical therapy routines.
• Address Fears: Reassure children that movement is safe when appropriately managed, which can help reduce anxiety about returning to activity.

Taking a person-centered approach, where the child is actively involved in their care, helps empower them to make good choices about activity levels and form, ultimately reducing the risk of future episodes of PFPS. By combining practical preventive steps with ongoing education, families can work together with healthcare providers to support knee health and keep children active and pain-free.

Recover Time for Patellofemoral Pain Syndrome

“Non-surgical treatments typically involve a combination of physical therapy, rest, and pain management. Physical therapy focuses on improving the strength and flexibility of the muscles around the knee, as well as correcting any muscle imbalances or alignment issues. A key element of rehabilitation is quadriceps strengthening, as stronger quadriceps can help stabilize the kneecap and reduce pain. Early in therapy, pain-free exercises are emphasized to avoid stressing the patellofemoral joint. For example:

• Straight-leg raises: With your child lying on their back, one knee bent and the other leg straight, they slowly lift the straight leg and hold it for 10 seconds before relaxing. This exercise can be performed with either static holds (isometric) or gentle movement (concentric/eccentric), making sure not to arch the back or compensate with the hips.
• Pillow squeeze exercise: Sitting comfortably with both knees extended, place a pillow or rolled towel under the affected knee. Your child gently presses down into the pillow by tightening their thigh muscle. This helps activate the quadriceps in a controlled, pain-free way.

Closed vs. Open Kinetic Chain Exercises

Your child’s physical therapist may also select exercises based on how much stress they place on the knee. Closed kinetic chain (CKC) exercises—such as squats—are often preferred, as they mimic real-life activities and generally produce less stress on the patellofemoral joint, especially when performed in the range of 0° to 40° of knee flexion. It’s important to ensure the knee doesn’t move past the toes during these movements, as this can increase joint stress and discomfort.

If CKC exercises are painful or not tolerated, open kinetic chain (OKC) exercises can be used. These allow for more controlled loading of the joint and should be performed within a pain-free range of motion, typically between 40° and 90° of knee flexion. By combining targeted exercises with rest and proper pain management, most children experience gradual improvement in symptoms and a steady return to their usual activities.”

Resting the knee and avoiding activities that aggravate the pain can also help alleviate symptoms. Doctors will also suggest pain management techniques, such as ice therapy and over-the-counter pain medications.

Exercise Therapy and Technique Retraining

Exercise is widely recognized as the cornerstone of PFPS treatment, with strong evidence supporting its effectiveness over rest alone. Physical therapists may prescribe individualized exercise programs aimed at strengthening both the knee and hip muscles. Research has shown that combining hip and knee strengthening can be especially beneficial, as both approaches are equally effective in reducing pain and improving function.

In addition to traditional strengthening exercises, retraining movement patterns, such as proper running technique, can help address abnormal kinematics that contribute to PFPS. For instance, reducing excessive hip adduction during movement has been linked to less knee pain, since increased hip adduction is a known risk factor for developing PFPS.

Progressive and Challenging Exercises

While basic exercises are often the starting point, recent studies suggest that more advanced or targeted exercises may be needed to fully address the underlying mechanisms of PFPS. Physical therapists may gradually introduce more complex exercises as your child’s strength and coordination improve, ensuring a comprehensive approach to recovery.

Conclusion

In conclusion, doctors consider PFPS a common condition that can cause pain and discomfort in the front of the knee. It is caused by a variety of factors, including overuse, improper alignment of the kneecap, muscle imbalances, and injury. Symptoms may include pain, swelling, and difficulty straightening the knee. Diagnosis is typically made through a physical examination and review of medical history. Non-surgical treatments such as physical therapy, rest, and pain management are often effective in treating PFPS.

However, in severe cases, surgery may become necessary. Prevention measures include maintaining proper form and technique during physical activity, wearing appropriate footwear, and incorporating strength and flexibility exercises into a regular exercise routine. Recovery time varies depending on the severity of the condition and the treatment approach.

If your child is experiencing pain in the knee, we strongly suggest that you contact a pediatric Orthopedic doctor. At the Medical City Children’s Orthopedics and Spine Specialists, we have several doctors who specialize in children, and we invite you to give us a call and make an appointment. For your convenience, we have five offices in Dallas, Arlington, Flower Mound, Frisco, and McKinney, TX.

When to Seek Specialist Referral

While many cases of knee pain can be managed with conservative treatments, there are certain situations where onward referral to a specialist is crucial:

• History of patella dislocation: If your child has previously dislocated their kneecap, a specialist evaluation is recommended.
• Direct blow to the knee: Especially if you suspect a patellar fracture or if pain and swelling do not improve, further investigation is warranted.
• Persistent instability: Repeated episodes of the kneecap slipping out of place (subluxation) that do not get better with physical therapy may indicate an underlying structural issue.
• Chronic, unresponsive pain: If your child’s knee pain is not improving with activity modification and typical management, or if there are signs of increased sensitivity (central sensitization), consider consulting a pain specialist.

Prompt attention to these warning signs can lead to appropriate treatment and help prevent further complications.

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Footnote:

American Academy of Orthopaedic Surgeons: Patellofemoral Pain Syndrome