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Total Knee Replacement

Background and Etiology

The knee is the largest joint in the body. It is built for weight bearing, stability and mobility. The knee complex is composed of four bones and three osseous bone-to-bone joints. These are the patellofemoral joint, tibiofemoral joint and the tibiofibular joint.

Bone and Joint

The tibiofemoral joint is a hinge joint, located between the largest bone in the body (the femur) and the larges bone in the lower leg (the tibia). When these two bones are joined together they form a medial and lateral compartment.

The second joint in the knee complex, called the patellofemoral joint, is located between the patellar (knee cap) and the femur. The patellar glides up and down a groove on the anterior distal aspect of the femur. There is also a joint between the small lateral bone of the lower leg (fibula) and the larger tibia.

At each joint the ends of the bones have a smooth shiny surface called joint articular cartilage that allows them to slide freely over each other.

Arthritis

Arthritis is the most common cause of a knee replacement. Arthritis is the wearing, degeneration or loss of articular cartilage in a joint. The three most common types of joint arthritis are osteoarthritis, rheumatoid arthritis, and traumatic arthritis. These different types of arthritis, in addition to severe fractures, can damage the knee joint so much that it functions very poorly. In these cases, a total or partial knee replacement may be necessary.

Causes

Osteoarthritis

The most common form of knee arthritis, Osteoarthritis is a gradual wearing and degeneration of the joint surfaces or articular cartilage. Osteoarthritis is most common in people who are middle age and adults over the age of 50. Women are more likely to develop osteoarthritis, and it can affect one knee or both. Knee osteoarthritis is the most common cause of disability.

Rheumatoid Arthritis

Unlike other forms of arthritis, rheumatoid arthritis is a systemic autoimmune disease that is not caused by common wear and tear on the joint. This condition usually affects joints symmetrically (for example, both shoulders). Rheumatoid arthritis causes degeneration of the articular or joint cartilage. It can also affect the tissue that surrounds and lubricates the joint (synovium). If the joint surfaces and cartilage are not lubricated they can start to rub, causing the wear that leads to arthritis pain.

Rheumatoid arthritis can affect other parts of the body including organs like the heart and lungs, and can even cause fatigue. The cause of Rheumatoid arthritis is not fully known. It is considered an autoimmune disease where the cells of the body attack themselves. Although it is a chronic condition, individuals can have periods with little to no symptoms mixed with acute or symptomatic periods. There can be a genetic component to this disease.

Traumatic Arthritis

Traumatic arthritis occurs as a result of blunt, penetrating, or repeated trauma to a joint. Damage to the articular cartilage can occur when extreme force or pressure is exerted on a joint, causing the cartilage to tear or break off into small pieces. These pieces can become lodged in the joint, where they will rub against the other joint structures. This trauma can make the joint weak, causing the inflammation and pain associated with arthritis.

Symptoms

  • Severe pain and aching in the knee
  • Loss of range of motion of the knee
  • Swelling around the joint
  • Increased size or visible deformity of the joint
  • Weakness that makes daily activities, particularly those that require jumping, bending, or twisting motions of the knee painful
  • A sensation of “cracking” or “crunching” in the knee joint
  • Stiffness, that can be extreme, causing tremendous difficulty moving the joint

Treatment

A knee replacement is a surgical procedure. The knee can be completely or partially removed and replaced with artificial material.

Total Knee Replacement

Total knee replacement may be indicated in severe cases of osteoarthritis, rheumatoid arthritis or traumatic arthritis. It may be indicated in the case of aseptic necrosis in which the circulation of the head of the femur is compromised resulting in degeneration of the knee joint.

There are several different designs of knee replacement devices. Most knee prosthetics consist of three components: the femoral component, typically made of a highly polished strong metal; the tibial component, typically made of a durable plastic often held in a metal tray; and the patellar component, typically also made of plastic.

Partial Knee Replacement

A partial knee replacement may be indicated in cases of cartilage damage that have not completely disrupted the function of the joint. In this procedure only part of the joint is replaced. Like a total joint replacement a partial joint replacement piece is typically made of either metal or plastic.

Physical Therapy Interventions

Physical Therapists are professionals, educated and trained to administer interventions. As defined by The Guide to Physical Therapist Practice, interventions are the skilled and purposeful use of physical therapy methods and techniques to produce changes consistent with the diagnosis, prognosis and the patient or client’s goals.

Following joint replacement surgery, an aggressive program of physical therapy interventions will be essential to recovering from the procedure and regaining range of motion and proper function of the knee complex. Common Physical Therapy interventions in the treatment of post surgical knee replacement include:

  • Manual Therapeutic Technique (MTT): Hands on care including soft tissue massage, stretching and joint mobilization by a physical therapist to improve alignment, mobility and range of motion of the knee. Use of mobilization techniques also help to modulate pain.
  • Therapeutic Exercises (TE) including stretching and strengthening exercises to regain range of motion for both knee extension (straightening) and flexion (bending) as well as strengthen muscles of the knee and lower extremity to support, stabilize and decrease the stresses place on joint cartilage and the knee joint.
  • Neuromuscular Reeducation (NMR) to restore stability, retrain the lower extremity, and improve movement techniques and mechanics (for example, walking, doing up or down stairs, kneeling, squatting, and balance activities) of the involved lower extremity during daily activities.
  • Modalities including the use of ultrasound, electrical stimulation, ice, cold, laser and others to decrease pain and inflammation of the involved joint.

Prognosis

Following surgery, it is important that the patient returns to full activity gradually. Instruction in daily activities and a comprehensive home program are helpful for regaining strength, range of motion, and improving balance. The prognosis following a total knee replacement is excellent. Rehabilitation following the surgery needs to be aggressive and may take four months. Patients can see improvement in function, strength, pain and range of motion for up to a year.