Epidermoid cysts are usually asymptomatic lesions, that slowly progress in size. They are formed by the invagination or the cystic expansion of hair follicles or epidermis. Most of the lesions are firm to fluctuant and dome-shaped ³ as seen in this patient. Very few cases (4 up till now) of the epidermal inclusion cyst have been described in the knee since it was first described in 2004 ³. Within the knee, these cysts can occur in the popliteal fossa or the prepatellar region ^1-2. With the history of trauma, possible differential of seroma could be considered.  

Treatment includes complete excision. However, a biopsy is required to rule out malignancy and infection, before surgery. Careful dissection to ensure complete removal of the lesion with its capsule is imperative. Bone curettage may be required ⁴. 

Differential diagnosis includes:

• Lipoma
• Abscess 
• Seroma
• Soft tissue sarcomatous changes
• Baker's cyst