Arthritis 

Osteoarthritis and rheumatoid arthritis commonly cause knee pain, stiffness, and swelling. 

Ligament Injuries 

Torn ligaments from sports or accidents can lead to instability and pain. 

Meniscus Tear 

Damage to knee cartilage causes pain, swelling, and difficulty moving the joint. 

Obesity 

Excess body weight increases pressure on knee joints, leading to pain and wear. 

Overuse or Strain 

Repeated movements, excessive exercise, or prolonged standing can strain the knee joint.