There are three basic types of arthritis that may affect the knee joint.
Osteoarthritis (OA) is the most common form of knee arthritis. OA is usually a slowly progressive degenerative disease in which the joint cartilage gradually wears away. It most often affects middle-aged and older people.
Rheumatoid arthritis (RA) is an inflammatory type of arthritis that can destroy the joint cartilage. RA can occur at any age. RA generally affects both knees.
Post-traumatic arthritis can develop after an injury to the knee. This type of arthritis is similar to osteoarthritis and may develop years after a fracture, ligament injury, or meniscus tear.
Generally, the pain associated with arthritis develops gradually, although sudden onset is also possible.
The joint may become stiff and swollen, making it difficult to bend or straighten the knee.
Pain and swelling are worse in the morning or after a period of inactivity. Pain may also increase after activities such as walking, stair climbing, or kneeling.
The pain may often cause a feeling of weakness in the knee, resulting in a “locking” or “buckling.”
Many people report that changes in the weather also affect the degree of pain from arthritis.