Knee arthritis

The knee has three compartments: the inner side (medial compartment), the outer side (lateral compartment) and the joint behind the kneecap (patellofemoral compartment). A smooth layer of cartilage covers the bone ends, and arthritis is the wearing away of that cartilage. As it thins, the bone underneath becomes irritated, which causes pain, swelling and stiffness. The medial and lateral compartments each have a secondary cushion called a meniscus, which usually degenerates and tears as the arthritis progresses. Meniscal tears and cartilage loss are part of the same degenerative process, and are not separate problems.

Osteoarthritis is the most common form and is more likely with age, earlier knee injury or surgery, family history and extra body weight. Inflammatory conditions such as rheumatoid arthritis can also damage the knee. Arthritis may affect one compartment or the whole knee, and that distinction guides treatment.

• Pain with walking, stairs, getting up from a chair or kneeling
• Stiffness after sitting or in the morning
• Swelling or a feeling that the knee is warm
• Grinding, catching, or a feeling that the knee gives way
• Bowing in or out of the leg
• Pain that wakes you at night

Your visit includes your history and an examination of the knee, hip and walking pattern. Standing X-rays show the loss of joint space and the alignment of the leg. MRI is not usually needed for arthritis and is ordered only when it will change the plan. Pain felt at the knee can come from the hip, so the hip is examined too.

Although nothing can remove arthritis other than surgery, many people can be helped for a time without surgery, particularly when the arthritis is in earlier stages.

Nonsurgical options include targeted physical therapy for muscle strengthening, activity changes, weight management, anti-inflammatory medication when it is safe, a brace or cane, and corticosteroid injections for temporary relief. Gel (hyaluronic acid) and platelet-rich plasma injections are also used. These measures may help to ease symptoms but do not reverse the arthritis, and injections almost never work well for advanced disease. See nonoperative hip and knee care for details, including which injections insurance covers.

Surgery is worth discussing when knee pain limits walking, stairs, sleep or the activities you care about despite a fair trial of nonoperative care, or when imaging shows advanced joint damage and nonoperative care is unlikely to improve symptoms. There is no single X-ray finding that decides it. The decision is based on how much the knee limits your life.

Waiting does not usually make the operation impossible, but very advanced arthritis can cause weakness and stiffness that take longer to recover from. The timing is a conversation between you and your surgeon.

When arthritis is limited to only one compartment and the ligaments are healthy, a partial knee replacement can resurface only the worn area and keep the rest of your knee. When arthritis involves more than one compartment, a total knee replacement resurfaces the ends of the thigh bone (femur), the shin bone (tibia), and the kneecap (patella), with durable metal and plastic parts.

While a partial knee replacement is a bit easier and faster to recover from, most studies and registries show it may not be as durable over the course of your lifetime.

Dr. Cooper plans each knee on a computer and uses a robotic arm to carry out the plan. See robotic knee replacement. Many knee replacements last for decades, and most people walk the day of surgery.