Ganglion cysts are among the most common soft-tissue masses found in the foot and ankle. These growths are non-cancerous, fluid-filled lumps that form near joints or tendons. They are a frequent occurrence in the lower extremities, often causing concern due to their sudden appearance or noticeable size.
What a Ganglion Cyst Is
A ganglion cyst is a sac filled with a thick, jelly-like substance, which is essentially synovial fluid—the natural lubricant found in joints and tendon sheaths. The cyst is not a true tumor but rather an outpouching of the tissue surrounding a joint or tendon.
The leading theory suggests they arise from irritation or degeneration of the joint capsule or tendon sheath. This microtrauma causes the tissue to weaken and bulge out, allowing the synovial fluid to escape and become encapsulated in a fibrous sac. Although benign, their location can still cause significant discomfort.
The fluid-filled nature of the cyst differentiates it from solid lumps like a lipoma or a fibroma. They are typically attached to deeper structures of the foot, such as the joint lining, by a small stalk. This connection allows the fluid to move into the cyst, sometimes causing the mass to fluctuate in size.
Where Ganglion Cysts Appear on the Foot
Ganglion cysts most often appear on the top (dorsum) of the foot and around the ankle joint. They can also develop near the toes, sometimes presenting as a mucinous cyst associated with the last joint of the toe.
When these cysts form, they cause symptoms beyond a noticeable lump, which can range in size from a pea to a golf ball. Pain is a frequent complaint, especially a dull ache that occurs when the cyst presses against an adjacent joint or tendon. The mass may become irritated by shoe pressure, making certain footwear difficult to wear comfortably.
A more concerning symptom is nerve compression, which can manifest as tingling, burning, or numbness. This happens when the cyst puts direct pressure on a nearby nerve. The cyst size may change over time, sometimes shrinking or disappearing spontaneously, only to reappear later.
How Health Professionals Confirm the Diagnosis
Health professionals, such as a podiatrist or orthopedist, typically begin with a thorough physical examination of the foot. The lump is palpated to assess its firmness, mobility, and tenderness. A classic test is transillumination: because the cyst is fluid-filled, shining a bright light against the mass causes it to glow, distinguishing it from a solid mass.
Imaging is often used to confirm the diagnosis and rule out other potential causes. X-rays are typically ordered first, not to visualize the cyst itself, but to assess the underlying bone structure. This helps rule out conditions like arthritis or a bony outgrowth that might be causing the swelling.
More detailed imaging, such as an ultrasound or Magnetic Resonance Imaging (MRI), confirms the fluid-filled nature of the mass. Ultrasound is effective for visualizing soft tissues and can show the cyst’s connection to the joint or tendon sheath. An MRI is particularly helpful for deeper or smaller cysts, providing precise anatomical localization and confirming the characteristic fluid signal.
Management Options
For small ganglion cysts that cause no pain or functional limitation, the initial approach is often watchful waiting. Many cysts will spontaneously decrease in size or disappear completely without intervention. Modification of footwear, such as wearing wider or softer shoes, can also help alleviate irritation from pressure over the mass.
If the cyst is persistent, painful, or causing nerve-related symptoms, two main procedural interventions are available. The first is aspiration, which involves draining the jelly-like fluid from the sac using a needle and syringe. While simple and quick, aspiration alone is associated with a high rate of recurrence, with studies reporting rates up to 78.1%.
The more definitive treatment is surgical excision, or surgical removal of the cyst. This procedure is typically reserved for cysts that are recurrent, cause significant pain, or interfere with mobility. The surgeon removes the entire cyst sac along with a portion of the attached joint capsule or tendon sheath, which is thought to be the source of the fluid. Although surgical excision offers a significantly lower recurrence rate (ranging from 5.7% to 43%), the cyst can still return.