Differential Diagnosis for 38-year-old Morbidly Obese Male with Right Knee Pain

• Single most likely diagnosis:
  • Patellofemoral Pain Syndrome (PFPS): Given the patient's history of knee pain since childhood, morbid obesity, and occupation that involves prolonged sitting, PFPS is a likely diagnosis. The pain is exacerbated by bending the knee, and there is tenderness around the anterior kneecap, which are characteristic findings in PFPS.
• Other Likely diagnoses:
  • Osteoarthritis (OA): The patient's morbid obesity and age put him at risk for OA, which can cause knee pain, stiffness, and swelling. Although OA is more common in older adults, the patient's obesity and occupation may have accelerated the wear and tear on his joints.
  • Prepatellar Bursitis: The patient's occupation as a truck driver, which involves frequent kneeling or direct pressure on the knee, increases the risk of prepatellar bursitis. The swelling and heat around the knee could be indicative of bursitis.
  • Tendinitis: The patient's knee pain and tenderness around the anterior kneecap could also be due to tendinitis, which is common in individuals who engage in repetitive activities that put stress on the tendons.
• Do Not Miss diagnoses:
  • Septic Arthritis: Although the patient denies any recent trauma or infection, septic arthritis is a medical emergency that requires prompt attention. The patient's severe pain, swelling, and heat around the knee could be indicative of septic arthritis, especially if he has a compromised immune system or a history of intravenous drug use.
  • Deep Vein Thrombosis (DVT): The patient's morbid obesity and prolonged sitting as a truck driver increase his risk of developing DVT. If the patient has a DVT, it could cause knee pain, swelling, and warmth, which could be mistaken for other conditions.
• Rare diagnoses:
  • Osgood-Schlatter Disease: Although the patient is an adult, Osgood-Schlatter disease can occur in adults who had the condition as adolescents. The disease causes knee pain, swelling, and tenderness below the kneecap.
  • Hoffa's Syndrome: This is a rare condition that causes knee pain and swelling due to inflammation of the infrapatellar fat pad. The patient's symptoms and occupation could be consistent with Hoffa's syndrome, although it is a rare diagnosis.