Differential Diagnosis for Knee Pain when Standing but OK when Moving

• Single most likely diagnosis
  • Osteoarthritis (OA) of the knee: This condition is characterized by wear and tear of the joint cartilage, leading to pain and stiffness, especially after periods of inactivity or when standing. The pain often improves with movement as the joint loosens up.
• Other Likely diagnoses
  • Meniscal tears: Tears in the cartilage of the knee can cause pain, especially when standing or putting weight on the knee. However, once the knee is moving, the pain may decrease as the torn pieces of cartilage move out of the way.
  • Bursitis: Inflammation of the fluid-filled sacs (bursae) that cushion the knee can cause pain when standing due to increased pressure on the bursae. Movement may help reduce this pressure, alleviating the pain.
  • Tendinitis: Inflammation of the tendons around the knee can cause pain when standing, which may improve with movement as the tendons warm up and become more flexible.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Septic arthritis: A bacterial infection within the knee joint can cause severe pain, especially when standing or moving the knee. Although the pain may seem to improve with movement in some cases, this condition requires immediate medical attention to prevent serious complications.
  • Osteonecrosis (avascular necrosis): A condition where the bone tissue dies due to lack of blood supply can cause knee pain that may improve with movement. However, if left untreated, it can lead to collapse of the bone and severe arthritis.
• Rare diagnoses
  • Complex regional pain syndrome (CRPS): A chronic pain condition that can cause severe, burning pain in the knee, among other symptoms. The pain pattern can be variable and may seem to improve with movement, but CRPS is a diagnosis of exclusion.
  • Neuropathic pain: Certain nerve conditions, such as neuropathy, can cause knee pain that may improve with movement. However, these conditions are less common causes of knee pain when standing but OK when moving.