Patellofemoral Pain Syndrome (PFPS), colloquially referred to as runner's knee, is a prevalent musculoskeletal disorder afflicts a broad demographic, although it is particularly prominent amongst individuals whose activities necessitate repetitive knee flexion and extension. In this article, we will delve into the intricate anatomy and the underlying biomechanics of the patellofemoral joint, the clinical manifestations, diagnostic evaluations, and the spectrum of therapeutic interventions with an emphasis on manual therapy and exercise-based rehabilitation strategies. By comprehensively exploring these aspects, we aim to equip readers with a deeper understanding of PFPS, fostering enhanced patient care and therapeutic outcomes.
Article Index:
Introduction
Examination & Diagnosis
Therapy and Exercise
Conclusion & References
Clinical Manifestations
Patients presenting with PFPS typically exhibit a combination of symptoms which are indicative of increased strain on the patellofemoral joint. These include:
Anterior Knee Pain: Predominantly, patients report a nondescript, aching discomfort localized around or posterior to the patella[5]. The pain quality is often described as dull or throbbing in nature.
Activity-Related Exacerbation: Symptoms tend to intensify during activities that load the patellofemoral joint. These activities encompass squatting, ascending or descending stairs, kneeling, or extended periods of sitting, often termed as "theatre sign" or "movie-goer's knee"[5].
Crepitus: Patients might perceive a grinding or grating sensation within the knee joint during movement, which is referred to as crepitus. This results from the friction between the patella and femur due to abnormal patellar tracking or degenerative changes[6].
Knee Instability: Some individuals might describe a sensation of the knee "giving way" or feeling unstable. This could be due to associated muscular weakness, proprioceptive deficits (the body's ability to perceive its location, movements, and actions), or as a protective response to pain[6].
Post-Activity Soreness: It is not uncommon for individuals with PFPS to experience delayed knee soreness or stiffness after periods of increased activity or prolonged rest.
It is important to note that the severity and combination of these symptoms can vary significantly between individuals, necessitating a comprehensive and individualized approach to assessment and treatment.
Anatomy and Biomechanics
Patellofemoral Pain Syndrome (PFPS) often arises due to excessive pressure or stress on the patellofemoral joint, a crucial part of the knee that is formed by the kneecap (also known as the patella) and the lower end of the thigh bone (femur)[1]. The kneecap acts like a lever, enhancing the force generated by the group of muscles at the front of your thigh (quadriceps), which play a key role in straightening the knee[2]. When functioning correctly, the kneecap moves within a groove at the end of the thigh bone, and this movement needs to be well-aligned and smooth to prevent excess strain on the joint.
The onset of PFPS is often due to a combination of factors, including imbalances in muscle strength or flexibility, improper movement patterns, and inherent or acquired structural variations in the knee[3]. For instance, weakness or tightness in the quadriceps, muscles on the side of your hip (hip abductors), or muscles that rotate your hip outwards (hip external rotators) can result in the kneecap moving in an abnormal or inefficient way. This faulty movement pattern can increase the strain on the patellofemoral joint, playing a significant role in the development of PFPS[4].
Patellofemoral Pain Syndrome (PFPS) involves several anatomical structures in and around the knee joint. Here's a list of the key structures:
Patella (Kneecap): The patella is a small, triangular bone that sits in front of the knee joint. It moves along a groove in the femur (trochlear groove) as the knee bends and straightens. Misalignment or improper movement of the patella can result in PFPS.
Femur (Thighbone): The lower end of the femur forms part of the knee joint. The trochlear groove at the end of the femur is where the patella tracks during knee movement.
Quadriceps Muscles and Tendons: These muscles at the front of the thigh are important for knee extension and help to stabilize the patella. The quadriceps tendon connects the muscles to the patella. Imbalances or weakness in these muscles can contribute to PFPS.
Patellar Tendon: This tendon connects the patella to the tibia (shinbone). The patellar tendon, along with the quadriceps muscle and quadriceps tendon, forms part of the knee's extensor mechanism, allowing us to straighten the knee.
Retinaculum: Medial and lateral retinacula (fibrous bands) help to stabilize the patella. Tightness or laxity in these structures can cause the patella to track improperly.
Cartilage: The undersurface of the patella and the end of the femur are covered with articular cartilage, a smooth substance that helps the bones glide easily against each other. Damage to this cartilage can contribute to PFPS.
Synovial Tissue: This is the joint capsule lining that secretes synovial fluid for lubrication. Inflammation of the synovial tissue can occur with PFPS.
Hip and Ankle Structures: While not directly part of the patellofemoral joint, muscles and structures at the hip and ankle can influence the alignment and mechanics of the knee. For example, weakness in the hip abductor and external rotator muscles or overpronation at the foot can contribute to PFPS.
It's important to remember that PFPS is often multifactorial, meaning it's not solely due to issues with one structure but rather a combination of factors that lead to the syndrome.
Diagnostic Evaluation
The diagnostic process for PFPS is multi-faceted, combining a detailed patient history with a comprehensive physical examination.
Orthopedic Testing:
Knee Examination - Effective Orthopaedic Testing This video provides a comprehensive guide to diagnosing common causes of knee pain through various orthopaedic examination techniques.
Neurological Testing:
Lower Limb Neuro Examination - The lower limb neurological examination assesses the motor and sensory neurons supplying the lower limbs to detect any impairment of the nervous system. This examination is used both as a screening and investigative tool.
Vascular Testing
Peripheral Vascular Examination - The peripheral vascular examination is a physical exam that evaluates the circulatory system outside of the heart and lungs. This exam is important in diagnosing and managing peripheral vascular diseases such as arterial occlusion, aneurysms, and venous insufficiency.
Imaging Modalities
X-rays:
Role: X-rays primarily provide a two-dimensional image of the bony anatomy of the knee joint, making them the initial choice for imaging in PFPS[9].
Rationale: X-rays are beneficial in assessing the overall alignment of the patella within the trochlear groove of the femur, evaluating for potential bone abnormalities or fractures, and checking for signs of osteoarthritis, such as reduced joint space.
Limitation: While X-rays are useful for evaluating the bone structure, they do not provide detailed information about soft tissues, including the cartilage, ligaments, and tendons.
Magnetic Resonance Imaging (MRI):
Role: MRI is employed to visualize soft tissue structures in the knee joint when a more comprehensive evaluation is required.
Rationale: MRIs offer a detailed view of the cartilage under the patella and on the femur, the quadriceps and patellar tendons, and the medial and lateral retinacula. They can detect soft tissue abnormalities that could contribute to PFPS, such as cartilage wear, inflammation, or damage to the tendons or ligaments.
Added Benefit: MRIs are instrumental in ruling out other knee pathologies that may mimic PFPS, such as meniscal tears or ligamentous injuries.
Differential Diagnosis
Given the complexity of the knee joint and the diversity of conditions that can manifest with similar symptoms, it is imperative to consider a range of differential diagnoses when evaluating a patient with PFPS. These include:
Iliotibial Band Syndrome (ITBS):
This condition involves inflammation of the iliotibial band, a thick band of fibrous tissue that runs down the outside of the leg. ITBS can present with lateral knee pain, which can be mistaken for PFPS, especially if the patient is an active individual or runner[10].
Differentiation from PFPS: Pain location is a significant distinguishing factor. ITBS typically causes pain on the outside of the knee, whereas PFPS generally involves anterior knee pain.
Meniscal Injuries:
The menisci are two crescent-shaped discs of cartilage that act as shock absorbers between the femur and tibia. Tears or damage to the meniscus can cause knee pain, swelling, and instability, which can mimic PFPS[10].
Differentiation from PFPS: Meniscal injuries often present with mechanical symptoms such as locking, catching, or a sense of giving way. The pain is typically more localized and may increase with direct pressure over the joint line.
Patellar Tendinitis:
Also known as jumper's knee, this condition involves inflammation of the patellar tendon, which connects the kneecap to the shinbone. Patellar tendinitis can cause anterior knee pain similar to PFPS[10].
Differentiation from PFPS: Patellar tendinitis pain is usually localized to the inferior aspect of the patella and is exacerbated by activities that involve explosive knee extension, such as jumping or sprinting.
Osteoarthritis (OA):
OA is a degenerative joint disease that can affect the knee. It can cause pain, stiffness, and functional impairment, resembling PFPS[10].
Differentiation from PFPS: OA often affects older individuals and is typically associated with morning stiffness that improves with activity. Radiographic imaging can provide definitive evidence of OA, showing joint space narrowing, osteophyte formation, and subchondral sclerosis.
A thorough and systematic evaluation is fundamental to distinguish these conditions from PFPS and to establish the most effective treatment strategy. Each condition has unique characteristics and treatment implications, underscoring the importance of accurate diagnosis.
Treatment & Exercise
An integrative approach that combines manual therapy with a tailored functional exercise program is strongly advocated to effectively manage PFPS. This approach aligns with the treatment philosophy of Motion Specific Release (MSR). The accompanying demonstration videos provide a few practical examples of MSR techniques and exercises commonly prescribed for PFPS management.
Motion Specific Release (MSR):
Knee Release Protocol
In the accompanying video, Dr. Abelson demonstrates an effective knee release protocol using Motion Specific Release (MSR) techniques. These procedures address the localized area of pain and the broader kinetic chain, contributing to a more comprehensive treatment approach.
4 Point MSR Knee Protocol
Effective Motion Specific Release knee mobility procedures are demonstrated in this video, which is extremely effective at addressing the body's entire kinetic chain. The femur, tibia, and patella, as well as many muscles and ligaments, make up the complicated structure of the knee joint.
Functional Exercises
Relieve Quadricep Pain - Lacrosse Ball
Many people have tight, restricted, and overactive quadriceps. This is because most people tend to overuse their quadriceps and adductors to perform lower extremity motions such as squats when they should actually be using their gluteals and hamstrings. This results in the development of muscle imbalances (strongly restricted quadriceps and weak hamstrings).
4 Point Band Leg Strengthening Exercises
This TheraBand exercise routine is specifically designed to target and strengthen four crucial muscle groups: Adductor, Abductor, Flexor, and Extensor muscles. These muscle groups play a vital role in maintaining stability, facilitating movement, and enhancing overall functional performance.
Conclusion
Patellofemoral Pain Syndrome (PFPS) is a prevalent musculoskeletal disorder characterized by anterior knee pain. Understanding its anatomy, biomechanics, and contributing factors is vital for the public and medical professionals. Diagnosis entails a thorough patient history, physical exam, and, when necessary, radiographic imaging, ensuring PFPS is distinguished from conditions with similar symptoms.
Effective PFPS treatment, such as the Motion Specific Release (MSR) system, combines manual therapy with functional exercises to address the condition's multifaceted nature. This method alleviates symptoms, rectifies imbalances, and prevents recurrence. Successful PFPS management emphasizes patient-clinician collaboration and commitment to a tailored treatment plan.
DR. BRIAN ABELSON DC. - The Author
Dr. Abelson's approach to musculoskeletal health care reflects a deep commitment to evidence-based practices and continuous learning. In his work at Kinetic Health in Calgary, Alberta, he integrates the latest research with a compassionate understanding of each patient's unique needs. As the developer of the Motion Specific Release (MSR) Treatment Systems, he views his role as both a practitioner and an educator, dedicated to sharing knowledge and techniques that can benefit the wider healthcare community. His ongoing efforts in teaching and practice aim to contribute positively to the field of musculoskeletal health, with a constant emphasis on patient-centered care and the collective advancement of treatment methods.
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References
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