Find out more about Partial Knee Replacement with the following link
- Bicompartmental Knee Resurfacing
- Unicondylar knee replacement
- Patellofemoral Knee Replacement
- Meniscal Cartilage Tears
Patellofemoral Knee Replacement
Normal Knee anatomy
The knee is essentially made up of four bones. The femur or thighbone is the bone connecting the hip to the knee. The tibia or shinbone connects the knee to the ankle. The patella (kneecap) is the small bone in front of the knee that rides on the knee joint as the knee bends. The fibula is a shorter and thinner bone running parallel to the tibia on its outside. The joint acts like a hinge but with some rotation.
The knee is a synovial joint meaning it is lined by synovium. The synovium produces fluid lubricating and nourishing the inside of the joint. Articular cartilage is the smooth surfaces at the end of the femur and tibia. It is the damage to this surface that causes arthritis.
The femur (thighbone) is the largest and the strongest bone in the body. It is the weight bearing bone of the thigh. It provides attachment to most of the muscles of the knee.
The two femoral condyles make up for the rounded end of the femur. Its smooth articular surface allows the femur to move easily over the tibial (shinbone) meniscus.
The tibia (shinbone), the second largest bone in the body, is the weight bearing bone of the leg. The menisci incompletely cover the superior surface of the tibia where it articulates with the femur. The menisci act as shock absorbers, protecting the articular surface of the tibia as well as assisting in rotation of the knee.
The fibula, although not a weight bearing bone, provides attachment sites for the lateral collateral ligaments (LCL) and the biceps femoris tendon.
The articulation of the tibia and fibula also allows a slight degree of movement, providing an element of flexibility in response to the actions of muscles attaching to the fibula.
The patella (kneecap), attached to the quadriceps tendon above and the patellar ligament below, rests against the anterior articular surface of the lower end of the femur and protects the knee joint. The patella acts as a fulcrum for the quadriceps by holding the quadriceps tendon off the lower end of the femur.
The medial and the lateral meniscus are thin C-shaped layers of fibrocartilage, incompletely covering the surface of the tibia where it articulates with the femur. The majority of the meniscus has no blood supply and for that reason, when damaged, the meniscus is unable to undergo the normal healing process that occurs in the rest of the body.
In addition, a meniscus begins to deteriorate with age, often developing degenerative tears. Typically, when the meniscus is damaged, the torn pieces begin to move in an abnormal fashion inside the joint.
The menisci act as shock absorbers protecting the articular surface of the tibia as well as assisting in rotation of the knee. As secondary stabilizers, the intact menisci interact with the stabilizing function of the ligaments and are most effective when the surrounding ligaments are intact.
Anterior Cruciate Ligament
The anterior cruciate ligament (ACL) is the major stabilizing ligament of the knee. The ACL is located in the center of the knee joint and runs from the femur (thigh bone) to the tibia (shin bone), through the center of the knee. The ACL prevents the femur from sliding backwards on the tibia (or the tibia sliding forwards on the femur). Together with the posterior cruciate ligament (PCL), ACL stabilizes the knee in a rotational fashion. Thus, if one of these ligaments is significantly damaged, the knee will be unstable when planting the foot of the injured extremity and pivoting, causing the knee to buckle and give way.
Posterior Cruciate Ligament (PCL)
Much less research has been done on the posterior cruciate ligament (PCL) because it is injured far less often than the ACL.
The PCL prevents the femur from moving too far forward over the tibia. The PCL is the knee’s basic stabilizer and is almost twice as strong as the ACL. It provides a central axis about which the knee rotates.
What is Arthritis?
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.
When arthritis affects the knee joint, it commonly occurs in two compartments, usually the medial and patellofemoral compartment. It is not common for a patient to have arthritis isolated to the patellofemoral compartment, but it does occur and is more commonly seen in women. Patellofemoral arthritis is diagnosed when the arthritic damage is only located in the patellofemoral compartment, affecting the back of the knee cap.
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)
Patellofemoral Arthritis or knee cap arthritis causes pain and decreased mobility that is usually localized to the front of the knee joint. The patellofemoral compartment is involved in activities such as walking up and down hills or stairs, kneeling or squatting and standing back up. These activities can be become almost impossible to do when the pain from the arthritic damage is severe enough. Patients with this type of arthritis usually have no pain when walking on flat surfaces even when walking long distances.
Evaluating the source of knee pain is critical in determining your treatment options for relief of the pain. Knee pain should be evaluated by an Orthopaedic specialist for proper diagnosis and treatment.
Your physician will perform the following:
- Medical History
- Physical Examination
Depending on what the history and exam reveal, your doctor may order medical tests to determine the cause of your knee pain and to rule out other conditions.
Diagnostic Studies may include:
- X-rays: X-rays are a form of electromagnetic radiation that is used to take pictures of bones. An X-ray can reveal if osteoarthritis from degenerative changes is causing your knee pain.
The diagnosis of osteoarthritis is made on history, physical examination & X-rays. There is no blood test to diagnose Osteoarthritis (wear & tear arthritis).
Conservative Treatment Options
Conservative treatment options refer to management of the problem without surgery.
Some conservative treatment measures for knee osteoarthritis include:
- Activity Modification and Limitations
- Weight Reduction
- Anti-inflammatory Medications
- Physical Therapy
- Orthotics such as canes, braces, or insoles
- Injection of steroid and analgesic into the knee joint
Patellofemoral Knee Replacement surgery may be recommended by your surgeon if you have osteoarthritis contained to the patellofemoral compartment and you have not obtained adequate relief with conservative treatment options.
Traditionally, a patient with only one compartment of knee arthritis would undergo a Total Knee Replacement surgery. Patellofemoral Knee Replacement is a minimally invasive surgical option that preserves the knee parts not damaged by arthritis as well as the stabilizing anterior and posterior cruciate ligaments, ACL and PCL. This less invasive bone and ligament preserving surgery is especially useful for younger, more active patients as the implant placed more closely mimics actual knee mechanics than does a total knee surgery.
The smaller implants used with a partial knee replacement surgery are customized to the patient’s anatomy based upon CT scans of the patient’s knee. A surgical Robotic Arm assists the surgeon with preoperative planning and intraoperative component placement, positioning, and alignment. Patellofemoral Knee Arthroplasty surgery will not alter the ability of the patient to eventually move to a Total Knee Replacement in the future should that become necessary.
Partial Knee Replacement surgery is performed in an operating room under sterile conditions with the patient under general anesthesia or spinal anesthesia with sedation. It is usually performed on an outpatient basis as day surgery.
- The surgeon makes a small incision, about 3-4 inches long over the knee.
- With the assistance of the robotic arm, the patellofemoral compartment is prepared for the artificial components by removing the damaged part of the patella and trochlea, the groove at the end of the femur.
- The new artificial components are fixed in place with the use of bone cement.
- The femoral component is made of polished metal and the patellar component looks like a plastic button which will glide smoothly in a groove located on the femoral component.
- With the new components in place, the knee is taken through a range of movements.
- Once the surgeon is satisfied with the results, the arthroscope and surgical instruments are removed and the incisions covered with a sterile dressing or biologic glue.
Post Operative Recovery
Common Post Operative guidelines include:
- You will be taken to the recovery room and monitored for any complications.
- You will be given pain medication to keep you comfortable at home.
- You will need someone to drive you home due to the drowsy effects of the anesthesia.
- Swelling is normal after knee surgery. Ice,compression, and elevation of the knee will be used to minimize swelling and pain.
- You will be given specific instructions regarding activity. Usually there are few activity restrictions.
- You will be referred to a rehabilitation program for exercise and strengthening.
- Eating a healthy diet and not smoking will promote healing.
Risks and Complications
- As with any major surgery there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages.
- It is important that you are informed of these risks before the surgery takes place.
Complications can be medical (general) or specific to knee surgery.Medical complications include those of the anesthetic and your general well being. Almost any medical condition can occur so this list is not complete. Complications include:
- Allergic reactions to medications
- Blood loss requiring transfusion with its low risk of disease transmission
- Heart attacks, strokes, kidney failure, pneumonia, bladder infections
- Complications from nerve blocks such as infection or nerve damage
- Serious medical problems can lead to ongoing health concerns, prolonged hospitalization, or rarely death.
Complications are rare after knee surgery, but unexpected events can follow any operation. Your surgeon feels that you should be aware of complications that may take place so that your decision to proceed with this operation is taken with all relevant information available to you.
Specific Complications related to Patellofemoral Knee Replacement surgery include:
- Infection: Infection can occur with any operation. In the knee this can be superficial or deep. Infection rates are approximately 1%. If it occurs it can be treated with antibiotics but may require further surgery.
- Deep Vein Thrombosis: DVT are blood clots that can form in the calf muscles and travel to the lung (Pulmonary embolism). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your surgeon.
- Ligament injuries: There are a number of ligaments surrounding the knee. These ligaments can be torn during surgery or break or stretch out any time afterwards. Surgery may be required to correct this problem.
- Injury to blood vessels or nerves: Also rare but can lead to weakness and loss of sensation in part of the leg. Damage to blood vessels may require further surgery if bleeding is ongoing.
- Arthrofibrosis: This is the development of thick, fibrous material around the joint that often occurs after joint injury or surgery and can lead to joint stiffness and decreased movement.
- Wear: The components eventually wear out over time, usually 10 to 15 years, and may need to be changed.
- Dislocation: An extremely rare condition where the ends of the knee joint lose contact with each other.
- Fractures or breaks: Can occur during surgery or afterwards if you fall. To fix these, you may require surgery.
Risk factors that can negatively affect adequate healing after knee arthroscopy include:
- Poor nutrition
- Age (over 60)
- Chronic Illness
- Steroid Use