Musculoskeletal strain: Given the bilateral nature and the duration of 2 weeks, musculoskeletal strain from overuse or repetitive strain injury is a common and likely cause. This could be due to increased physical activity, poor posture, or direct trauma to the muscles.

Overuse injury: Similar to musculoskeletal strain, overuse injuries such as runner's knee or thigh splints could cause bilateral upper leg pain, especially in individuals who have recently increased their physical activity levels.
Peripheral neuropathy: Conditions affecting the nerves, such as diabetic neuropathy or peripheral neuropathy due to other causes, could lead to bilateral leg pain. However, this typically presents with additional symptoms like numbness or tingling.
Vitamin deficiencies: Deficiencies in vitamins like B12 can cause neurological symptoms, including pain in the legs. This would be less common but should be considered, especially in individuals with dietary restrictions or malabsorption issues.

Deep vein thrombosis (DVT): Although less common, DVT is a critical diagnosis that must not be missed due to its potential for severe complications, including pulmonary embolism. Bilateral leg pain could be a symptom, especially if accompanied by swelling, redness, or warmth.
Aortic occlusion: Acute aortic occlusion can cause severe, bilateral leg pain and is a medical emergency. This condition would typically present with additional symptoms like decreased pulses in the legs and potentially abdominal pain.
Spinal stenosis: While more commonly associated with lower back pain, severe spinal stenosis can cause radiating pain down the legs. This condition might not be the first consideration for bilateral upper leg pain but is crucial to identify due to its impact on mobility and quality of life.

Polymyalgia rheumatica: An inflammatory condition that causes muscle pain and stiffness, typically in the shoulders and hips, but can also affect the upper legs. It's more common in older adults and often accompanied by other systemic symptoms.
Eosinophilia-myalgia syndrome: A rare condition characterized by muscle pain and elevated eosinophil counts. It's associated with certain medications and toxins.
Neoplastic processes: Rarely, bilateral leg pain can be a symptom of metastatic disease affecting the bones or soft tissues of the legs. This would be an uncommon presentation but should be considered in the differential diagnosis, especially in patients with a known history of cancer.