Differential Diagnosis for Knee Pain and Clicking with Stinging Sensation

• Single most likely diagnosis:
  • Patellofemoral Pain Syndrome (PFPS): This condition is characterized by pain around or behind the patella, often accompanied by clicking or grinding sensations. The stinging feeling in the skin when flexing over the patella could be related to the irritation of the soft tissues or the patellar tendon, which is commonly seen in PFPS. The age and symptoms of the patient align well with this diagnosis.
• Other Likely diagnoses:
  • Chondromalacia Patellae: This condition involves the softening of the cartilage on the underside of the patella, leading to knee pain and tenderness. The clicking or grinding sensation, along with pain when flexing the knee, could indicate chondromalacia patellae.
  • Patellar Tendinopathy: Also known as jumper's knee, this condition involves inflammation of the patellar tendon, leading to pain and stiffness, especially when jumping, squatting, or climbing stairs. The stinging sensation could be related to the tendon's inflammation.
  • Meniscal Tear: Although less likely given the specific symptoms, a meniscal tear could cause pain and clicking in the knee. However, the stinging sensation in the skin is less typical for meniscal tears.
• Do Not Miss diagnoses:
  • Deep Vein Thrombosis (DVT): Although the primary symptoms do not strongly suggest DVT, any condition involving the lower extremities, especially if there's swelling or warmth, should prompt consideration of DVT due to its potential for severe complications.
  • Osteonecrosis of the Knee: This condition involves the death of bone tissue due to lack of blood supply. It can cause severe knee pain and should be considered, especially if the patient has risk factors such as steroid use or significant trauma.
• Rare diagnoses:
  • Plica Syndrome: This involves irritation of the synovial folds within the knee joint, which can cause pain, clicking, and snapping sensations. It's less common but could be considered if other diagnoses are ruled out.
  • Neuroma: A benign growth of nerve tissue can cause stinging or burning sensations. Although rare in the context of knee pain and clicking, it should be considered if the pain has a distinct neuropathic character.