Residual Limb Pain (RLP) or Stump Pain: This condition is common in patients with amputations, characterized by pain in the residual limb. The patient's recent adjustments to the leg and history of amputation make this a likely cause. The description of burning, shooting, stabbing, and sharp pain, along with tenderness to palpation, is consistent with RLP.

Pressure Ulcer or Skin Breakdown: Given the patient's recent adjustments to the prosthetic leg and the presence of significant tenderness to palpation on the medial aspect of the left leg, a pressure ulcer or skin breakdown is a plausible diagnosis. These conditions can cause localized pain and tenderness.
Prosthetic Fit Issues: An improper fit of the prosthetic device can lead to localized pressure, friction, and subsequent pain, especially if there have been recent adjustments.
Neuroma: A neuroma, which is a growth of nerve tissue, can develop at the site of the amputation and cause pain, especially if it is irritated by the prosthetic or if there are fit issues.

Deep Vein Thrombosis (DVT): Although the patient had normal blood flow and clot testing two weeks ago, the possibility of a new DVT cannot be entirely ruled out, especially if there have been changes in mobility or other risk factors. DVT is a potentially life-threatening condition that requires immediate attention.
Osteomyelitis or Infection of the Residual Limb: Despite the lack of fever and recent normal blood tests, an infection in the residual limb is a critical diagnosis not to miss. Infections can present subtly, especially in patients with compromised circulation or those taking antibiotics, which might mask some symptoms.
Compartment Syndrome: This is a condition where pressure within the muscles builds to dangerous levels, decreasing blood flow. It is less common in the setting of a chronic amputation but could occur, especially with recent adjustments or changes in activity level.

Complex Regional Pain Syndrome (CRPS): This is a chronic pain condition characterized by severe, burning pain at the site of an injury. While it could be considered, the patient's presentation and history make it less likely compared to other diagnoses.
Nerve Entrapment or Compression: This could occur due to the prosthetic or anatomical changes post-amputation. However, it is less common and would typically present with more specific neurological symptoms.
Bone Spur or Heterotopic Ossification: These are conditions where bone grows in abnormal places, which could cause pain and tenderness. They are less common and might be considered if other diagnoses are ruled out.

Clinical Examination: A thorough examination of the residual limb, including assessment of the fit of the prosthetic device, inspection for signs of skin breakdown or infection, and palpation for tenderness.
Imaging: Consider X-rays to evaluate the bone and soft tissues of the residual limb. An MRI could be useful for assessing soft tissue, including the presence of neuromas or other abnormalities.
Laboratory Tests: Complete blood count (CBC) and erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) to assess for signs of infection or inflammation, even though recent tests were normal.
Vascular Assessment: If there's any suspicion of vascular issues, consider a Doppler ultrasound to assess blood flow.
Pain Management Consultation: For guidance on managing chronic pain, especially if the pain is determined to be related to the amputation itself.
Prosthetic Adjustment: Consultation with a prosthetist to ensure proper fit and function of the prosthetic device.