Atraumatic Lateral Knee Pain With Inner Thigh “Bubble” - Driving And Climbing Stairs

HISTORY: A 36-year old female presented to the sports medicine office with constant right knee pain for the past year that started shortly after giving birth. She denied history of trauma. Her knee pain was lateral, deep, and sharp. She reported radiation from thigh down her calf and paresthesias with crossing her legs. The pain was worse with walking and rising from a seated position and maneuvering stairs and driving. She reported improvement with rest and nonsteroidal anti-inflammatory medication. Additionally, she reported limping and a “bubble in thigh” present for a month, stable in size without overlying skin changes. She denied fevers, night sweats, or weight loss. PHYSICAL EXAMINATION: Examination in office revealed intact strength bilaterally, except right knee extension, which was limited with pain. She had intact sensation and full ROM of lower extremities. She had palpable firmness of soft tissue of medial thigh with a well-circumscribed and moveable mass. Palpation of the mass was non-painful. She had an antalgic gait, protecting her right lower extremity. Additionally, straight leg raise on her right side caused lateral knee pain to extend down the lateral calf. She also had a positive lateral McMurray test. DIFFERENTIAL DIAGNOSIS: 1. Lumbar radiculitis 2. Meniscal pathology 3. Benign soft tissue lesion 4. Malignant soft tissue lesion TESTS AND RESULTS: Right Femur Radiographs: — Revealed normal appearing soft tissues without fracture or bony lesions. Lumbar radiographs: — Revealed normal disc spaces, normal appearing sacroiliac joints, normal facet joints, and no listhesis with flexion or extension. FINAL WORKING DIAGNOSIS: Nodular Fasciitis TREATMENT AND OUTCOMES: 1. The patient’s inner thigh mass was evaluated with MRI. 2. The MRI revealed a well-circumscribed mass within the distal vastus medialis muscle that was likely a neurogenic tumor, but soft tissue sarcoma could not be excluded. 3. The patient was referred to an orthopedic oncologist who recommended biopsy and frozen section of the mass. 4. The patient underwent resection of the soft tissue mass. Pathology revealed right nodular fasciitis of the quadriceps muscle.