The knee joint is like a hinge joint with the primary movement being bending (flexion) and straightening (extension). There are some other additional movements like gliding and rolling when the knee flexes and extends. It is composed of three bones: the end of thigh bone femur (femur), the top of the shin bone (tibia) and the patella (knee cap). The bones are covered with smooth cartilage surfaces that act as a cushion and permits smooth gliding movement. The strong ligaments connect the bones and provide front-to-back and side-to-side stability. The powerful muscles attach to the bones through tendons and contribute to the stability of the knee. In addition there are 2 special 'C' shaped cartilages between the femur and tibia, which act as shock absorbers.
Osteoarthritis (OA) is a disease that wears down the joint cartilage so that the joint no longer moves smoothly. The roughened surface and progressive loss of cartilage results in pain, stiffness, feeling of weakness, clicking and grinding sensation in the knee. Any activities that involve loading the knee joint such as walking long distances, standing for prolonged periods of time, climbing up and down stairs makes the pain worse. In severe cases, the pain may occur even at rest. Some people have to put a pillow or soft cushion between the legs to reduce the pain. Over time, as the cartilage might be worn way more on one side of the side of the knee, some people might notice deformities of the knee such as being knock-kneed or bow-legged.
Rheumatoid arthritis (RA), on the other hand, is an inflammatory arthritis and usually affects multiple joints including the hands. Unlike osteoarthritis, the pain in rheumatoid arthritis is worse after rest and inactivity and joints may become warm, red and swollen, especially in the morning. Patients with RA are treated with specific medications to reduce the inflammatory process. Other causes of arthritis are infection, known as septic arthritis and injury, post-traumatic arthritis.
Some of the risk factors include family history of arthritis, large body mass, muscle weakness, previous trauma to the knee and increased age.
The diagnosis is usually made by physical examination and weight bearing x-rays of the knee. The characteristic findings on x-rays are narrowing of the joint space, bony spurs (osteophytes), eburnation of the bone, cyst in the bone. In severe cases with significant cartilage loss, one might see bones touching each other. On some occasions, the surgeon might request special x-rays of the knee cap and even a MRI scan to exclude any other causes of knee pain.
Non-operative treatment is the first line of treatment for all patients. Rest, limited activity and analgesia are the first line of advice. Anti-inflammatory medications are recommended in patients with no contra-indications. I advise always consulting a doctor before taking such medications. Weight loss reduces the stress on the knee joint. Low impact aerobic exercises and physiotherapy helps in maintaining function without overstressing the joint. A combination of supervised exercises and home program have shown excellent results. Walking with a stick in the opposite hand may help reduce the pain by distributing some of the load.
Injections into the joint can provide temporary symptomatic relief but prolonged or repeated injections are not recommended due to their potential adverse effects.
If the non-operative methods have failed, surgery may be the only option left. The exact type of surgery depends on the age, the underlying condition and the anatomy of the knee. Arthroscopic knee washout or debridement (Keyhole) is not usually recommended in patients with established osteoarthritis of the knee because it might not necessarily provide with long term relief.
Hight tibial osteotomy is a surgery where the upper half of the tibia (shin bone) is cut and realigned to unload the arthritic area and reduce the stresses across one compartment of the knee by diverting the weight on relatively uninvolved part of the knee. This is indicated in young patients with arthritis affecting compartment of the knee. Unicompartmental (partial) knee replacement is also a good surgical option in patients with isolated disease affecting one compartment of the knee. A total knee replacement is indicated in patients with symptomatic generalised osteoarthritis affecting the knee. In knee replacement surgery, an artificial implant or prosthesis is used to replace the damaged, worn out surfaces on the end of the bones. These implants are usually fixed to the bone with surgical cement.