Summary

A Ganglion Cyst is the most common soft tissue mass of the foot and ankle. It is a benign, mucin-filled cyst that herniates from a joint capsule or tendon sheath. Unlike wrist ganglia (volar/dorsal), foot ganglia face severe mechanical pressure from footwear. The most common location is the Dorsal Midfoot (over the TMT or TN joints). While benign, they can cause significant pain due to direct compression of the Deep Peroneal Nerve or simple friction against the shoe tongue. Treatment is stepwise: Observation/Shoe change, Aspiration (high recurrence), or Surgical Excision (requiring meticulous tracing of the "stalk" to the joint to prevent return). [1,2,3]

Key Facts

• The Contents: Filled with a thick, clear, jelly-like fluid (hyaluronic acid/mucin). It is not pus, and it is not simple joint fluid (it is hyper-concentrated).
• The "Bible Cyst": Historically smashed with a heavy Bible. This bursts the cyst wall. Recurrence was common (and painful). Not recommended.
• The Pump: Ganglions act as a one-way valve. Fluid pumps out of the joint into the cyst but can't get back in. This is why they fluctuate in size (bigger after activity, smaller after rest).

Clinical Pearls

"Turn out the lights": Transillumination is the cheapest and best diagnostic test. A ganglion lights up like a lightbulb. Solid tumors (GCT, Sarcoma) do not.

"The hidden Arthritis": A dorsal foot ganglion in an older patient is often a sentinel sign of underlying TMT arthritis. The cyst is just the tip of the iceberg; the joint degeneration is the cause.

"Beware the Pulse": Always palpate before you stick a needle in. A dorsalis pedis artery aneurysm can look exactly like a ganglion.

                 DORSAL FOOT LUMP
                        ↓
            TRANSILLUMINATION POSITIVE?
            ┌───────────┴───────────┐
          YES                      NO
      (Ganglion)            (Solid Tumor, etc.)
           ↓                        ↓
      SYMPTOMATIC?              ULTRASOUND/MRI
      ┌────┴────┐              (Investigate)
     NO        YES
     ↓          ↓
  OBSERVE    ASPIRATION (+/- Corticosteroid)
  WIDER SHOE    ↓
             RECURRED?
                ↓
             SURGERY
        (Excision of Stalk)

Protocol

• Reassurance: "It's not cancer." 40% spontaneously resolve.
• Shoe Wear: Loosen laces. Skip lacing.
• Aspiration:
  • Large bore needle (18G) required due to jelly thickness.
  • Success: 50% cure rate. 50% recurrence.
  • Steroid: Adding steroid lowers recurrence slightly.

Excision

• Indication: Pain, Nerve compression, Failed aspiration.
• Technique:
  • Loupe magnification is helpful.
  • Dissect the cyst free from the neurovascular bundle (DP Artery/Nerve).
  • Trace the Stalk: Follow the neck down to the joint capsule.
  • Capsulotomy: Excise a small patch of the capsule (the root) to prevent the valve mechanism from reforming.
• Outcome:
  • Recurrence: 5-10% (if stalk removed).
  • Recurrence: 40% (if just "popped").

Aspiration vs Excision

• Dias et al: A 10-year study showed that aspiration cures ~40-50% of ganglia. Surgery cures 90%. Therefore, aspiration is a reasonable first-line treatment due to low morbidity.

Arthroscopic Resection

• Ankle Ganglia: Anterior ankle ganglia can be resected arthroscopically (shaver), avoiding large incisions and scarring.

The Lump

It's a balloon filled with joint jelly. The valve is stuck "open", so fluid pumps in when you walk, but can't get out.

The Options

1. Leave it alone: If it doesn't hurt, ignore it. It might go away.
2. Drain it: I can stick a needle in it. 50/50 chance it comes back.
3. Cut it out: A small surgery. We have to dig down to the root to stop it recurring.

Q1: What is the fluid inside a ganglion? A: A viscous, clear, mucinous fluid rich in Hyaluronic Acid, Glucosamine, and Globulins. It is thicker than synovial fluid.

Q2: Differentiate a Ganglion from a Synovial Cyst. A:

• Ganglion: No synovial lining (fibrous wall). Mucinous degeneration.
• Synovial Cyst: Lined by true synovium (often in RA). Herniation of joint.
• Clinically, they are treated similarly.

Q3: Describe the path of the Deep Peroneal Nerve on the dorsum of the foot. A: It runs alongside the Dorsalis Pedis Artery, deep to the Extensor Hallucis Brevis tendon, supplying sensation to the 1st Webspace. This is exactly where midfoot ganglia occur.

Q4: Why is a Bible used historically? A: It was the heaviest book in the house. The blunt force trauma ruptured the cyst wall, dispersing the fluid into the tissues.

(End of Topic)