The knee joint is formed by three bones – femur (thigh bone), tibia (leg bone) and the patella (kneecap).
The knee works like a hinge, but there is some gliding and rotational movement too. Thus, the knee is a modified hinge joint. The femur connects separately with the tibia and the patella. The patella is attached to the tibia through the patellar tendon. The knee joint is stabilized internally by the anterior and the posterior cruciate ligaments (ACL and PCL); and externally by the medial and the lateral collateral ligaments (MCL and LCL). In addition, the knee contains two semilunar cartilages, the medial meniscus and the lateral meniscus, which change the contour of the end of the femur, thus facilitating better load trasfer across the joint.The ends of the bones which come in contact with each other are covered with articular cartilage, which acts as a shock-absorber.
In knee arthritis, there is destruction of the cartilage between the femur and tibia, thus exposing the underlying bone.
Further wear of the bones causes changes like osteophyte formation (bone spurs at the edge of the joint) and synovitis (thickening of joint cover). The meniscus (medial and lateral) gets eroded. The undersurface of the patella also shows similar changes. In addition, there is loss of alignment, leading to deformity of the knee.
The knee joint sometimes swells up with fluid (effusion). The patient has pain in the knee, which can be felt in the front, back or on the sides of the knee. Pain is felt at rest and also during any movement in the knee joint, such as sitting cross-legged, squatting or getting up from sitting position. Weight-bearing activities like walking and climbing up or down the stairs are painful. In severe arthritis the patient is severely disabled with pain, and begins to avoid activities like stair-climbing and walking more than a few feet at a time.
A thorough clinical examination is followed by a set of blood tests, X-Rays and other investigations. The changes seen on the X-Ray in an arthritic knee are
Patients with mild to moderate knee arthritis can be usually treated with painkillers, physiotherapy, weight reduction and lifestyle modifications.
However, in severe arthritis of the knee, medications will relieve pain only for a short duration, while their prolonged use will be harmful to the stomach, liver and kidneys. In such cases, one may consider total knee replacement (TKR) surgery as an effective and permanent solution. TKR can relieve pain and restore the patient to near-normal level of daily activities.