Differential Diagnosis for Sudden Onset Left Knee Pain

Single Most Likely Diagnosis

• Meniscal Tear or Ligament Sprain: This is a common cause of sudden knee pain, especially if the patient has recently experienced trauma or stress on the knee joint. The recent use of a pressure washer could have led to a sudden movement or twist that resulted in a meniscal tear or ligament sprain.

Other Likely Diagnoses

• Tendinitis or Bursitis: Inflammation of the tendons or bursae around the knee joint can cause sudden pain, especially if the patient has been engaging in activities that involve repetitive knee movements.
• Osteoarthritis: Although less common in a 37-year-old male, osteoarthritis can cause sudden knee pain, especially if there is a history of trauma or repetitive stress on the joint.
• Septic Arthritis: Although the subcutaneous laceration has healed, there is still a risk of septic arthritis, especially if the laceration became infected.

Do Not Miss Diagnoses

• Osteomyelitis: A bone infection that can occur if bacteria from the laceration site spread to the bone. This is a serious condition that requires prompt treatment.
• Septic Arthritis: As mentioned earlier, septic arthritis is a serious condition that requires prompt treatment. If left untreated, it can lead to permanent joint damage.
• Deep Vein Thrombosis (DVT): Although less common, DVT can cause knee pain and swelling, especially if the patient has been immobile or has a history of clotting disorders.

Rare Diagnoses

• Gout or Pseudogout: These conditions can cause sudden, severe knee pain, but are less common in a 37-year-old male with no previous medical history.
• Hemarthrosis: Bleeding into the joint space can cause sudden knee pain, but is typically associated with trauma or bleeding disorders.
• Bone Tumor: A bone tumor can cause knee pain, but is a rare condition that would typically be associated with other symptoms such as weight loss or night pain.