Differential Diagnosis for 73-year-old Female Patient

The patient presents with a complex set of symptoms including difficulty standing due to lack of strength, swollen knees, fatigue, recurrent falls, and a history of various medical conditions. Given this clinical picture, the differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis
  • Osteoarthritis with possible superimposed infection: The patient's history of joint pain in multiple sites, swelling in both knees, and recent development of a sore that became infected behind her left leg, suggests a possible osteoarthritis flare-up complicated by a localized infection. The infection could have contributed to her current state of weakness and difficulty in mobilizing.
• Other Likely Diagnoses
  • Diabetic Neuropathy exacerbation: Given her history of diabetic peripheral neuropathy, an exacerbation could explain her difficulty in standing and walking, as neuropathy can cause significant pain, weakness, and balance issues.
  • Chronic Kidney Disease (CKD) or Heart Failure exacerbation: The patient is on Lasix (furosemide), which is used to treat fluid build-up due to heart failure, liver disease, or kidney disorder. An exacerbation of heart failure or CKD could lead to increased fluid retention, explaining the swelling and possibly contributing to her fatigue and weakness.
  • Vitamin D deficiency: Although unspecified, a significant vitamin D deficiency can lead to muscle weakness and bone pain, which could exacerbate her mobility issues.
• Do Not Miss Diagnoses
  • Septic Arthritis: Given the history of a sore that became infected, there's a risk that the infection could have spread to the joints, particularly the knees, which are swollen. Septic arthritis is a medical emergency requiring prompt diagnosis and treatment.
  • Deep Vein Thrombosis (DVT): The patient's history of swelling, particularly if asymmetric, and recent immobility due to falls, increases her risk for DVT. This condition can lead to pulmonary embolism if not addressed.
  • Infection leading to Sepsis: The patient's recent history of an infected sore and current state of weakness and fatigue could indicate an ongoing infectious process potentially leading to sepsis, a life-threatening condition.
• Rare Diagnoses
  • Rheumatoid Arthritis or other Autoimmune Arthropathies: Although less likely given the patient's age and presentation, these conditions can cause significant joint swelling, pain, and systemic symptoms like fatigue.
  • Musculoskeletal infections like Pyomyositis: This is a rare infection of the muscle that could explain the patient's weakness and the development of a sore that became infected.

Each of these diagnoses requires careful consideration of the patient's history, physical examination, and potentially, further diagnostic testing to determine the underlying cause of her symptoms and to guide appropriate management.