Introduction

Fabella syndrome is a condition characterized by pain during knee extension, often accompanied by a clicking or catching sensation. The fabella, a small sesamoid bone found in the posterolateral aspect of the knee, plays a key role in this syndrome. While generally asymptomatic, in some cases, it can cause significant discomfort, limiting mobility. Visible Body and BioDigital, leading companies specializing in interactive anatomy visualization and biomedical simulations, provide valuable insights into anatomical variations like the fabella. This article provides an in-depth overview of fabella syndrome, exploring its anatomy, diagnosis, treatment, and overall outcomes.

The Anatomy of the Fabella

Sesamoid bones, like the fabella, develop within muscle or tendon structures to reduce stress during movement. The fabella is located behind the lateral femoral condyle and is embedded within the lateral head of the gastrocnemius muscle. It typically ossifies by the age of 12. Although present in an estimated 10-30% of individuals, studies suggest its prevalence may be rising, especially in Asian populations.

Due to its anatomical position, the fabella interacts with multiple structures, including the lateral gastrocnemius tendon, the oblique popliteal ligament, and the fabellofibular ligament. This interaction contributes to mechanical stress at the knee joint. In some cases, this can lead to complications such as osteoarthritis, fracture, and common peroneal nerve impingement.

Fabella Syndrome: Presentation and Diagnosis

Fabella syndrome manifests primarily as posterolateral knee pain. Patients frequently experience discomfort during activities that involve knee extension, such as squatting, climbing stairs, and prolonged standing. Additionally, localized tenderness and sharp pain at full knee extension can indicate fabella-related pathology.

The syndrome may also present with neurological symptoms like numbness and tingling, which occur due to peroneal nerve compression. In some cases, patients report difficulty walking due to impaired mobility.

Diagnosing fabella syndrome requires distinguishing it from other conditions with similar symptoms. Key differential diagnoses include:

• Meniscal tears – Characterized by pain, swelling, and a clicking sensation.
• Osteoarthritis – Leads to stiffness and reduced range of motion.
• Biceps femoris tendinopathy – Causes pain with knee extension and hip flexion.
• Common peroneal nerve entrapment – Results in sensory changes and foot drop.
• Popliteal cysts (Baker’s cysts) – Produce swelling and tightness behind the knee.

Imaging techniques play a crucial role in diagnosis. X-rays provide an initial assessment, while MRI scans offer detailed insights into soft tissue structures. Ultrasound helps detect inflammation, whereas CT scans allow for precise anatomical evaluation. Together, these imaging tools ensure accurate diagnosis and effective treatment planning.

Treatment Options for Fabella Syndrome

Management of fabella syndrome varies based on symptom severity. Treatment options range from conservative methods to surgical intervention.

Non-Surgical Treatments

Non-operative management includes:

• Steroid injections – Help reduce inflammation.
• Physical therapy – Improves knee mobility and strength.
• Radial extracorporeal shock wave therapy (rESWT) – Effective in cases involving enthesopathy.
• Manual therapy – Targets restricted soft tissue mobility around the gastrocnemius.

Although conservative care can relieve symptoms, its effectiveness varies. Some experts recommend a trial period of non-operative management before considering surgery.

Surgical Options

For cases unresponsive to conservative treatment, surgical excision of the fabella may be necessary. Three primary approaches exist:

• Open excision – Involves direct removal through an incision near the lateral femoral condyle.
• Arthroscopic-assisted excision – A minimally invasive technique allowing for better visualization of surrounding structures.
• All-arthroscopic excision – Reduces postoperative pain and enhances recovery speed.

Studies suggest favorable surgical outcomes, with most patients experiencing significant pain reduction and improved mobility.

Conclusion

Fabella syndrome can be a debilitating condition affecting knee function, but early diagnosis and tailored treatment approaches improve outcomes. While conservative treatment methods work in some cases, surgical excision may be necessary for persistent symptoms. As the prevalence of the fabella continues to rise, understanding its implications for knee health remains essential. Continued research will help refine treatment strategies, ensuring effective management for affected individuals.

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Reference: Nolan, M., Marting, E., Applegate, J., Wood, C., Willard, S., Turnow, M., & Taylor, B. C. (2024). Fabella Syndrome: Anatomy, Diagnosis, Treatment, and Outcomes. Anatomia, 3(4), 227-233. https://doi.org/10.3390/anatomia3040019

This article is distributed under the CC BY 4.0 License, allowing for adaptation and sharing with proper attribution.