Differential Diagnosis for Right Knee Pain Radiating to Calf

Single Most Likely Diagnosis

• Muscle Strain or Overuse Injury: This is often the most common cause of knee pain that radiates down to the calf, especially in individuals who are physically active. The pain can result from strain or overuse of the muscles in the knee or calf.

Other Likely Diagnoses

• Ligament Sprain: Sprains of the ligaments around the knee, such as the anterior cruciate ligament (ACL) or medial collateral ligament (MCL), can cause pain that radiates down to the calf due to the ligaments' attachments and the referred pain patterns.
• Meniscal Tear: Tears in the cartilage of the knee joint can cause pain, especially with twisting motions, and this pain can sometimes radiate down to the calf.
• Tendinitis: Inflammation of the tendons around the knee, such as patellar tendinitis, can cause pain that may radiate down towards the calf.
• Bursitis: Inflammation of the bursae around the knee can cause localized pain but may also radiate pain down to the calf due to the proximity of the bursae to the tendons and ligaments.

Do Not Miss Diagnoses

• Deep Vein Thrombosis (DVT): Although less common, DVT is a potentially life-threatening condition that can cause pain in the calf and sometimes the knee. It's crucial to consider this diagnosis, especially in patients with risk factors such as recent surgery, immobilization, or cancer.
• Popliteal Artery Aneurysm or Thrombosis: These vascular conditions can cause severe pain in the knee and calf and are medical emergencies.
• Osteonecrosis (Avascular Necrosis): This condition, where the bone tissue dies due to lack of blood supply, can cause severe pain and is more common in certain populations (e.g., long-term steroid users).

Rare Diagnoses

• Peripheral Nerve Entrapment: Conditions like peroneal nerve entrapment or tarsal tunnel syndrome can cause pain, numbness, and tingling in the distribution of the affected nerve, potentially causing knee pain that radiates to the calf.
• Bone Tumors: Both benign and malignant bone tumors can cause localized pain that may radiate; these are less common but important to consider in the differential diagnosis.
• Infectious or Inflammatory Arthritis: Conditions like septic arthritis or rheumatoid arthritis can cause knee pain that may radiate down to the calf, especially if there is significant inflammation or infection.