Differential Diagnosis for Knee Complaint

The patient's complaint of a "squigly" at the front of the knee following a trauma more than 10 years ago suggests several potential diagnoses. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Anterior Cruciate Ligament (ACL) Injury: The patient's history of trauma and complaint of knee weakness, along with the description of a "squigly" which might imply instability or a feeling of the knee giving way, points towards an ACL injury. ACL injuries are common after knee traumas and can lead to chronic instability if not properly addressed.

• Other Likely Diagnoses

  • Meniscal Tear: Meniscal tears can occur from trauma and may cause chronic knee pain and instability. The "squigly" feeling could be interpreted as a mechanical symptom such as locking or catching, which is common in meniscal tears.
  • Patellofemoral Pain Syndrome (PFPS): This condition involves pain around or behind the patella, often related to trauma, overuse, or biomechanical issues. While it might not directly cause a "squigly" feeling, it could contribute to a sense of instability or weakness, especially if the patient has developed patellar maltracking or other associated issues.
  • Osteoarthritis: Post-traumatic osteoarthritis could be a consideration, especially if the initial trauma led to joint damage. However, the "squigly" description is less typical for osteoarthritis, which usually presents with pain, stiffness, and decreased function.

• Do Not Miss Diagnoses

  • Osteosarcoma or Other Bone Tumors: Although rare, a bone tumor could present with a history of trauma and chronic symptoms. It's crucial to consider this possibility, especially if there's a significant delay in diagnosis or if the patient reports night pain or other red flag symptoms.
  • Infection (e.g., Osteomyelitis, Septic Arthritis): Infections can occur post-trauma and may present with chronic pain, swelling, or instability. While less likely given the long timeframe since the trauma, it's essential not to miss these diagnoses due to their potential for serious complications.
  • Neurological Conditions (e.g., Peroneal Nerve Palsy): Trauma can cause nerve damage, leading to weakness or instability. A thorough neurological examination is necessary to rule out such conditions.

• Rare Diagnoses

  • Patellar Tendonitis or Rupture: While more common in athletes, patellar tendon issues could cause anterior knee pain and a feeling of instability.
  • Bursitis: Prepatellar or infrapatellar bursitis could cause swelling and pain at the front of the knee, potentially leading to a feeling of instability or weakness.
  • Ligamentous Laxity: Generalized ligamentous laxity could contribute to the patient's feeling of knee weakness and instability, though this would typically be a more generalized condition rather than localized to one knee.