Knee

Introduction

Dr. Paul Peters specializes in Knee Replacement Surgery, using minimally invasive techniques. Since 1992, Dr. Peters has performed hundreds of knee surgeries each year in Dallas. Dr. Peters’ goal is to restore the normal activity level of both the young and old patient receiving a knee replacement. Dr. Peters is an advocate of using new less-invasive techniques, and better materials for the active patient with a knee replacement.

Anatomy

The knee is a complex joint made up of different structures including bones, tendons, ligaments and muscles. They all work together to maintain normal function and provide stability to the knee during movement.

Having a well-functioning healthy knee is essential for our mobility and ability to participate in various activities. Understanding the anatomy of the knee enhances your ability to discuss and choose the right treatment procedure for knee problems with your doctor.

Bones

The Knee is a hinge joint made up of two bones, the thigh bone (femur) and the shinbone (tibia). There are two round knobs at the end of the femur called femoral condyles which articulate with the flat surface of the tibia called the tibial plateau. The tibia plateau on the inside of the leg is called the medial tibial plateau, and on the outside of the leg it is called the lateral tibial plateau.

The two femoral condyles form a groove on the front (anterior) side of the knee called the patellofemoral groove. A small bone called the patella sits in this groove and forms the knee cap. It acts as a shield and protects the knee joint from direct trauma.

A fourth bone called the fibula is the other bone of the lower leg. This forms a small joint with the tibia. This joint has very little movement and is not considered a part of the main joint of the knee.

Articular Cartilage and Menisci

Movement of the bones causes friction between the articulating surfaces. To reduce this friction, all articulating surfaces involved in movement are covered with a white, shiny, slippery layer called articular cartilage. The articulating surface of the femoral condyles, tibial plateaus and the back of the patella are covered with this cartilage. The cartilage provides a smooth surface that facilitates easy movement.

To further reduce friction between the articulating surfaces of the bones, the knee joint is lined by a synovial membrane which produces a thick clear fluid called synovial fluid. This fluid lubricates and nourishes the cartilage and bones inside the joint capsule.

Within the knee joint between the femur and tibia there are two C shaped cartilaginous structures called menisci. Menisci function to provide stability to the knee by spreading the weight of the upper body across the whole surface of the tibial plateau. The menisci help in load bearing by preventing the weight from concentrating onto a small area, which could damage the articular cartilage. The menisci also act as a cushion between the femur and tibia by absorbing the shock produced by activities such as walking, running and jumping.

Ligaments

Ligaments are tough bands of tissue that connect one bone to another bone. The ligaments of the knee function to stabilize the knee joint. There are two important groups of ligaments that hold the bones of the knee joint together, collateral ligaments and the cruciate ligament.

Collateral ligaments are present on either side of the knee. They function to prevent the knee from moving too far during side to side motion. The collateral ligament on the inside is called the medial collateral ligament (MCL) and the collateral ligament on the outside is called the lateral collateral ligament (LCL).

Cruciate ligaments- This group of ligaments, present inside the knee joint, control the back and forth motion of the knee. The Cruciate ligament in the front of the knee is called anterior cruciate ligament or ACL and the cruciate ligament in the back of the knee is called posterior cruciate ligament or PCL.

Muscles

Muscles: There are two major muscles, the quadriceps and the hamstrings, which enable movement of the knee joint. The quadriceps muscles are located in the front of the thigh. When the quadriceps muscles contract, the knee straightens. The hamstrings are located in the back of the thigh. When the hamstring muscles contract, the knee bends.

Tendons

Tendons are structures that attach muscles to the bone. The quadriceps muscles of the knee meet just above the patella and attach to it through a tendon called the quadriceps tendon. The patella further attaches to the tibia through a tendon called the patella tendon. The quadriceps muscle, quadriceps tendon and patellar tendon all work together to straighten the knee. Similarly, the hamstring muscles at the back of the leg are attached to the knee joint with the hamstring tendon.

Conditions

Arthritis of Knee Joint

Arthritis is a general term covering numerous conditions where the joint surface or cartilage wears out. The joint surface is covered by a smooth articular surface that allows pain free movement in the joint. This surface can wear out for a number of reasons; often the definite cause is not known.

When the articular cartilage wears out the bone ends rub on one another and cause pain. This condition is referred to as Osteoarthritis or “wear and tear” arthritis as it occurs with aging and use. It is the most common type of arthritis.

Causes of Arthritis

There are numerous conditions that can cause arthritis but often the exact cause is never known. In general, but not always, it affects people as they get older (Osteoarthritis).

Other causes include:

  • Trauma (fracture)
  • Increased stress such as overuse and overweight
  • Infection of the bone
  • Connective tissue disorders
  • Inactive lifestyle and Obesity (overweight); Your weight is the single most important link between diet and arthritis as being overweight puts an additional burden on your hips, knees, ankles and feet.
  • Inflammation (Rheumatoid arthritis)

Symptoms

Knee Arthritis causes pain and decreased mobility of the knee joint. In the arthritic knee there is an absent joint space that shows on X-ray. In the normal knee there is a normal joint space.

Arthritic knee

The cartilage lining is thinner than normal or completely absent. The degree of cartilage damage and inflammation varies with the type and stage of arthritis. The capsule of the arthritic knee is swollen. The joint space is narrowed and irregular in outline; this can be seen in an X-ray image. Bone spurs or excessive bone can also build up around the edges of the joint. The combinations of these factors make the arthritic knee stiff and limit activities due to pain or fatigue.

Knee Pain

The knee is one of the largest joints in the body, formed by the lower end of the femur, upper end of the tibia and the patella or knee cap. Several ligaments and muscles attach to the bones of the knee joint to maintain normal motion of the joint. Special cartilaginous tissues known as menisci are placed between the two articular ends of the joint. These act as a cushion between the articular surfaces and absorb the shock during movement.

Knee pain is a common condition affecting individuals from different age groups. It not only affects movement but also impacts the quality of life of the individual. An injury or disease of the knee joint or any structure surrounding the knee can result in knee pain. A precise diagnosis of the underlying cause is important to develop an appropriate treatment plan.

Some of the common causes for knee pain include:

  • Arthritis: a condition associated with inflammation of the joint
  • Knee ligament injuries
  • Torn meniscus
  • Patellar tendonitis: inflammation of the patellar tendon which connects the kneecap to the shin bone
  • Chondromalacia patellae: softening of the articular cartilage on the under surface of the kneecap causing knee pain
  • Dislocated kneecap
  • Baker's cyst: a fluid-filled swelling in the back of the knee which usually results from another problem such as a meniscus tear
  • Knee bursitis: inflammation of the bursae, small fluid-filled sacs located around the joints, usually between a tendon and the bone.
  • Plica syndrome: results from inflammation of the synovial tissue of the knee causing knee pain and swelling.
  • Osgood-Schlatter disease: caused by irritation of the growth plate at the front of the knee joint and is more common in adolescents
  • Osteochondritis dissecans: characterized by detachment of a cartilage fragment and a thin layer of the bone from the end of a bone due to inadequate blood supply; these fragments may either stay in place or slide around the joint causing pain and joint instability
  • Gout: characterized by sudden, severe attacks of joint pain, with swelling and redness around the joint, caused by accumulation of uric acid crystals in the joints

Diagnoses

Knee conditions should be evaluated by your doctor for a proper diagnosis and treatment. A detailed medical history and physical examination of the knee are crucial for the diagnosis. Your doctor may also conduct diagnostic imaging studies such as X-rays, MRI scans, CT scans, and ultrasound. Blood tests may be performed to identify any infection, gout or pseudogout. Sometimes arthrocentesis may also be performed, wherein the fluid from the knee joint is removed and sent for laboratory analysis.

Treatment

Treatment options depend upon the underlying cause responsible for knee pain. Some of the common treatment options for knee pain include rest, ice and heat application, nonsteroidal anti-inflammatory medications, stretching, physical therapy and cortisone injections.

Sometimes a knee arthroscopy may be performed. Knee arthroscopy is a surgical procedure in which the internal structures of the joint are examined to diagnose as well as treat the underlying problem.

If you experience difficulty or inability to walk, deformity around the joint, inability to bend the knee, knee pain persisting beyond a few days and more at night, or pain associated with swelling, warmth, or redness, you should consult your doctor for immediate medical intervention.

Treatments

Total Knee Replacement (TKR)

Total knee replacement, also called total knee arthroplasty, is a surgical procedure in which the worn out or damaged surfaces of the knee joint are removed and replaced with artificial parts. The knee is made up of the femur (thigh bone), the tibia (shin bone), and patella (kneecap). The meniscus, the soft cartilage between the femur and tibia, serves as a cushion and helps absorb shock during motion. Arthritis (inflammation of the joints), injury, or other diseases of the joint can damage this protective layer of cartilage, causing extreme pain and difficulty in performing daily activities. Your doctor may recommend surgery if non-surgical treatment options have failed to relieve the symptoms.

Indications

Total knee replacement surgery is commonly indicated for severe osteoarthritis of the knee. Osteoarthritis is the most common form of knee arthritis in which the joint cartilage gradually wears away. It often affects older people.

In a normal joint, articular cartilage allows for smooth movement within the joint, whereas in an arthritic knee the cartilage itself becomes thinner or completely absent. In addition, the bones become thicker around the edges of the joint and may form bony “spurs”. All of these factors can cause pain and restricted range of motion in the joint.

Your doctor may advise total knee replacement if you have:

  • Severe knee pain which limits your daily activities (such as walking, getting up from a chair or climbing stairs).
  • Moderate to severe pain that occurs during rest or awakens you at night.
  • Chronic knee inflammation and swelling that is not relieved with rest or medications
  • Failure to obtain pain relief from medications, injections, physical therapy, or other conservative treatments.
  • A bow- legged knee deformity

Causes

The exact cause of osteoarthritis is not known, however there are a number of factors that are commonly associated with the onset of arthritis and may include:

  • Injury or trauma to the joint
  • Fractures at the knee joint
  • Increased body weight
  • Repetitive overuse
  • Joint infection
  • Inflammation of the joint
  • Connective tissue disorders

Diagnosis

Your doctor will diagnose osteoarthritis based on the medical history, physical examination, and X-rays.

X-rays typically show a narrowing of the joint space in the arthritic knee.

Procedure

The goal of total knee replacement surgery is to relieve pain and restore the alignment and function of your knee.

The surgery is performed under spinal or general anesthesia. Your surgeon will make an incision in the skin over the affected knee to expose the knee joint. Then the damaged portions of the femur bone are cut at appropriate angles using specialized jigs. The femoral component is attached to the end of the femur with or without bone cement. The surgeon then cuts or shaves the damaged area of the tibia (shinbone) and the cartilage. This removes the deformed part of the bone and any bony growths, as well as creates a smooth surface on which the implants can be attached. Next, the tibial component is secured to the end of the bone with bone cement or screws. Your surgeon will place a plastic piece called an articular surface between the implants to provide a smooth gliding surface for movement. This plastic insert will support the body's weight and allow the femur to move over the tibia, similar to the original meniscus cartilage. The femur and the tibia with the new components are then put together to form the new knee joint. To make sure the patella (knee cap) glides smoothly over the new artificial knee, its rear surface is also prepared to receive a plastic component. With all the new components in place, the knee joint is tested through its range of motion. The entire joint is then irrigated and cleaned with a sterile solution. The incision is carefully closed, drains are inserted and a sterile dressing is placed over the incision.

Post-operative care

Rehabilitation begins immediately following the surgery. A physical therapist will teach you specific exercises to strengthen your leg and restore knee movement. Knee immobilizers are used to stabilize the knee. You will be able to walk with crutches or a walker. A continuous passive motion (CPM) machine can be used to move the knee joint. Continuous passive motion is a device attached to the treated leg which constantly moves the joint through a controlled range of motion, while the patient relaxes. Your physical therapist will also provide you with a home exercise program to strengthen thigh and calf muscles.

Risks and complications

As with any major surgery, possible risks and complications associated with total knee replacement surgery include:

  • Knee stiffness
  • Infection
  • Blood clots (deep vein thrombosis)
  • Nerve and blood vessel damage
  • Ligament injuries
  • Patella (kneecap) dislocation
  • Plastic liner wears out
  • Loosening of the implant

If you find difficulty in performing simple activities such as walking or climbing stairs because of your severe arthritic knee pain, then total knee replacement may be an option for you. It is a safe and effective procedure to relieve pain, correct leg deformity, and help you resume your normal activities of daily living

Revision Knee Replacement

Revision knee replacement surgery involves replacing part or all of your previous knee prosthesis with a new prosthesis. Although total knee replacement surgery is successful, sometimes the procedure can fail due to various reasons and require a second revision surgery.

Disease Overview

The knee joints are lined by soft articular cartilage that cushion the joints and aid in smooth movement of the joint bones. Degeneration of the cartilage due to wear and tear leads to arthritis, which is characterized by severe pain.

Total Knee Replacement

During total knee replacement, the damaged cartilage and bone is removed from the knee joint and replaced with artificial components. Artificial knee joints are usually made of metal, ceramic or plastic and consist of the femoral component and the tibial component.

Indications

Revision knee replacement surgery may be advised to patients if they have one or more of the following conditions:

  • Trauma to the knee joint
  • Chronic progressive joint disease
  • Increased pain in the affected knee
  • Worn out prosthesis
  • Knee instability or a feeling of giving way while walking
  • Loosening of the prosthesis
  • Infection in the prosthetic joint
  • Weakening of bone around the knee replacement, a process known as osteolysis (bone loss)
  • Stiffness in the knee
  • Leg length discrepancy
  • Fracture

Surgical procedure

Revision knee replacement surgery may involve the replacement of one or all of the components.

The surgery is performed under general anesthesia. Your surgeon makes an incision over the knee to expose the knee joint. The kneecap along with its ligament may be moved aside so that there is enough room to perform the operation. Then the old femoral component of the knee prosthesis is removed. The femur is prepared to receive the new component. In some cases, the damaged bone is removed and bone graft or a metal wedge may be used to make up for the lost bone.

Next the tibial component along with the old plastic liner is removed. The damaged bone is cut and the tibia is prepared to receive the new component. Similar to the femur, the lost bone is replaced either by a metal wedge or bone graft. Then, a new tibial component is secured to the end of the bone using bone cement. A new plastic liner will be placed on the top of the tibial component. If the patella (kneecap) has been damaged, your surgeon will resurface and attach a plastic component. The tibial and femoral components of the prosthesis are then brought together to form the new knee joint, and the knee muscles and tendons are reattached. Surgical drains are placed for the excess blood to drain out and the incision is closed.

Risks and complications

Like all major surgical procedures, there may be certain risks and complications involved with revision knee replacement surgery. The possible complications after revision knee replacement include:

  • Stiffness in the knee
  • Infection
  • Bleeding
  • Formation of blood clots in the leg veins
  • Injury to nerves or blood vessels
  • Prosthesis failure
  • Patella (kneecap) dislocation
  • Ligament injuries

Postoperative care

Following revision knee replacement surgery, a Continuous passive motion (CPM) machine may be used to allow the knee joint to slowly move. The machine is attached to the treated leg which slowly moves the joint through a controlled range of motion, while you relax.

You can walk with crutches or a walker. You will be sent for rehabilitation within a couple days of surgery. A physical therapist will teach you specific exercises to strengthen your leg and restore range of motion to the knee. Your physical therapist will also provide you with a home exercise program to strengthen thigh and calf muscles.

Knee immobilizers are used when performing physical therapy, walking and while sleeping in order to keep the knee stabilized.

Revision knee replacement surgery is performed to replace failed knee prosthesis with a new prosthetic component. The surgery improves mobility and enables you to return to normal activities with a pain-free knee.

Minimally Invasive Knee Joint Replacement

Total knee replacement is a surgical procedure in which the damaged or worn cartilaginous surfaces of the knee are replaced with prostheses or implants in order to relieve pain and improve movement. Traditionally, this procedure is performed by making a long incision to access the knee joint. Minimally invasive knee joint replacement uses new technology to achieve the same results with a smaller incision and less tissue damage. This technique minimizes postoperative pain and reduces recovery time.

Knee replacement involves removal of the damaged cartilage, preparation of the bones to receive the implants and placement of the implants. During minimally invasive procedures, the implants used are the same however special instruments are used to prepare the bones and muscle sparing techniques are used to approach the knee without damaging the surrounding tissue. Following surgery, physical therapy is recommended to improve strength and range of motion.

Minimally invasive knee joint replacement may not be suitable for all individuals. Your doctor will recommend this procedure depending on your condition. Generally, healthy patients without previous history of knee injuries or surgeries find better results.

As with any procedure, minimally invasive knee joint replacement may be associated with certain complications such as infection, delayed wound healing, nerve and vessel damage and improper placement of implants.

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  • American Association of Hip and Knee Surgeons
  •  American Academy of Orthopaedic Surgeons
  • North Central Surgical Center Hospital
  • Texas Health Presbyterian Hospital Dallas
  • Texas Scottish Rite Hospital for Children
  • Healthgrades