The Knee

Knee replacement surgery  - also known as Total Knee Arthroplasty -  can help relieve pain and restore function in severely diseased knee joints.  It is the most frequently-performed orthopedic surgery, with more than 300,000 knee replacement surgeries performed each year in the United States.

A Healthy Knee

The knee joint is the largest joint in our bodies and is considered a hinge joint because it allows the knee to bend or flex and straighten or extend. While hinges can only bend, the knee joint also has the ability to rotate (twist) and translate (slide). The knee joint is formed by the upper end of the leg bone, the tibia, and the lower end of the thigh bone, the femur.  In addition, a bone within the quadriceps tendon, the knee cap or patella also is a part of the knee joint. The knee joint is thought to comprise three parts:

• the medial compartment (inner aspect of the knee)

• the lateral compartment (the outer aspect of the knee)

• the patellofemoral compartment (where the knee cap slides on the end of the thigh bone)

In a total knee replacement, all three parts of the knee are resurfaced. In a unicompartmental knee replacement, either the inside (medial) compartment or outside (lateral) compartment is replaced. 

An Arthritic Knee

The various types of arthritis damage the smooth gliding surfaces (articular cartilage) of the joint resulting in bone on bone surface contact.  This results in stiffness, pain, limitation in motion and in some cases swelling. 

Non-Surgical Treatments for Knee Arthritis

In the early stages of arthritis, there are non-surgical treatments that can help manage knee discomfort. These include:

• Limiting activities that aggravate the knee (but without becoming sedentary)

• Using a cane to decrease the force applied to the knee

• Gentle exercises to maintain muscle tone and range of motion

• Losing weight if obesity is a contributing factor

• Cortisone injections into the knee (a limited number times)

• Non-Steroidal Anti-Inflammatory Drugs to decrease inflammation

Knee Replacement Surgeries

Knee replacement surgery is a highly effective treatment for severe arthritis of the knee. It is is in essence a joint resurfacing procedure. It eliminates pain and restores mobility by removing the diseased bone and replacing worn out cartilage with a prosthesis of metal surfaces and a plastic gliding interface.

Partial Knee Replacement

Unicompartmental Arthroplasty is sometimes appropriate for patients who have just the medial compartment (most commonly) or the lateral compartment (less commonly) of the knee affected with arthritis. This involves resurfacing the end of the thigh bone and the upper end of the leg bone on just the worn side. Size-matched metal components are cemented onto the ends of the bones after the arthritic surfaces have been removed.  A small piece of high-grade medical plastic called polyethylene is snapped into the lower of the two pieces. 

Rehabilitation from this minimally invasive procedure is typically quicker than from a traditional total knee replacement and possibly from a minimally invasive total knee replacement. The Unicompartmental Arthroplasty procedure preserves the healthy joint surfaces and only replaces the worn joint surfaces.

Total Knee Replacement

Traditional total knee replacement involves an incision of 8-10 inches, with a splitting of the quadriceps tendon and turning the knee cap backwards (eversion of the knee cap) to give access to the joint surfaces for resurfacing. Just the worn out surfaces are removed and replaced with the joint components (called prostheses).  Cutting of the quadriceps tendon and flipping the knee cap results in damage to the muscle and tendon, with resultant loss of strength, swelling, and increased pain. Some studies have shown that the muscle may take several years to fully recover from the weakness caused by the underlying disease process as well as from being cut during the surgery to resurface the joint surfaces.  This healing process also slows down the return of knee motion.

The Minimally Invasive Quadriceps-Sparing knee replacement uses a much smaller 3-5 inch incision. It either completely spares the quadriceps muscle and tendon from cutting, or uses just a small one inch split to the muscle to gain access to the joint.  By using specialized instruments and a ‘mobile window’ of skin and capsular tissue, high flex total knee components are used to replace the damaged surfaces of the knee. Studies of minimally invasive knee replacements have shown that recovery times and post-operative pain are both significantly reduced when compared to traditional total knee replacements. Look at the relative incision sizes for each and you'll see why.

Comparing Incisions for Traditional and MIS Knee Surgeries

Compared to the Traditional knee replacement, a Minimally Invasive Quad-Sparing knee replacement results in:

• significantly less pain

• less blood loss

• a shorter stay in the hospital (typically 1 ½ to 2 days)

• rapid return of knee motion

• an accelerated return to work and recreational activities

With the minimally invasive technique, the quadriceps muscle has not been cut, and patients are allowed to immediately bear weight fully on their replaced knee, frequently on the day of surgery.

Dr. Woods has some patients who have had knee replacement surgery to one knee using the traditional technique and the other knee using the new minimally invasive technique. They are enthusiastic about the differences, typically describing the minimally invasive knee as being  "a month ahead of the traditional knee in regards to pain level and function." 

Pain Management

In addition to careful attention to the surgical technique, Dr. Woods also uses the latest in pre-operative, intra-operative and post-operative pain management.  As a result, his patients typically describe their pain both while in the hospital as well as after returning home as ‘more like an ache.’