Myositis ossificans (MO) is a rare disorder of ectopic ossification in soft tissue or muscle, usually associated with trauma or hereditary conditions. Surgical excision is the mainstay of treatment with anti-inflammatory medications. Radiotherapy is used as an adjuvant therapy, to treat residual lesions and to relieve symptoms.

A 36-year-old male presented with a localised tender swelling in left popliteal fossa and progressive pain in lower limb for 6 weeks and restricted mobility for 3 weeks. A local excision of calcified mass arising from fascia of left popliteal fossa was consistent with MO features. Due to persistent symptoms and a residual lesion on imaging, adjuvant external beam radiation therapy (EBRT) was planned with a low dose of 10 Gy (Gray) in 2 fractions on 2 consecutive days in a prone position after 2 weeks using 6 MV (mega voltage) photon beam on linear accelerator (LINAC).

Radiotherapy resulted in a significant clinical improvement without any related acute toxicities. Patient is disease-free and on regular follow-up without any progression after 2 years.

Post-operative EBRT can stabilise residual MO and treat intractable pain when lesion lies in the vicinity of a neurovascular bundle