Knee Anatomy

The knee joint is one of the most complex and largest joints of the body. The lower end of the thighbone (femur) meets the upper end of the shinbone (tibia) at the knee joint. A small bone called the patella (kneecap) rests on a groove on the front side of the femoral end. A bone of the lower leg (fibula) forms a joint with the shinbone.

To allow smooth and painless motion of the knee joint, articular surfaces of these bones are covered with a shiny white slippery articular cartilage. Two C-shaped cartilaginous menisci are present in between the femoral end and the tibial end.

Menisci act as shock absorbers, providing cushion to the joints. Menisci also play an important role in providing stability and load bearing to the knee joint.

Bands of tissue, including the cruciate and collateral ligaments, keep the different bones of the knee joint together and provide stabilization to the joint. Surrounding muscles are connected to the knee bones by tendons. The bones work together with the muscles and tendons to provide mobility to the knee joint. The whole knee joint is covered by a ligamentous capsule, which further stabilizes the joint. This ligamentous capsule is also lined with a synovial membrane that secretes synovial fluid for lubrication.

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 of the Knee

The knee is a hinge joint made up of two bones, the thighbone (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 form 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 of the Knee

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 of the Knee

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 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 of the Knee

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

Tendons of the Knee

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.

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.

Baker’s Cyst

The knee consists of a fluid called synovial fluid, which reduces friction between the bones of the knee joint while you move your leg. Sometimes this fluid is produced in excess, resulting in its accumulation in the back of your knee. A Baker’s cyst or popliteal cyst is a fluid-filled swelling that develops into a lump behind the knee. This causes stiffness, tightness and pain behind your knee. It is commonly seen in women and people aged over 40 (although it can develop at any age).

ACL Tears

The anterior cruciate ligament, or ACL, is one of the major ligaments of the knee that is in the middle of the knee and runs from the femur (thighbone) to the tibia (shinbone). It prevents the tibia from sliding out in front of the femur. Together with posterior cruciate ligament (PCL) it provides rotational stability to the knee.

MCL Tears

The medial collateral ligament (MCL) is the ligament that is located on the inner part of the knee joint. It runs from the femur (thighbone) to the top of the tibia (shinbone) and helps in stabilising the knee.

Meniscal Injuries

The knee is one of the most complex and largest joint in the body, and is more susceptible to injury. Meniscal tears are one among the common injuries to the knee joint. It can occur at any age, but are more common in athletes playing contact sports.

Ligament Injuries

The knee is a complex joint which consists of bone, cartilage, ligaments and tendons that make joint movements easy and at the same time more susceptible to various kinds of injuries.

Knee problems may arise if any of these structures get injured by overuse or suddenly during sports activities. Pain, swelling, and stiffness are the common symptoms of any damage or injury to the knee.

Knee 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 several reasons; often the definite cause is not known.

There are three basic types of arthritis that may affect the knee joint:

Osteoarthritis

Osteoarthritis (OA) is the most common form of knee arthritis. OA is usually a slowly progressive degenerative disease in which the joint cartilage gradually wears away. It most often affects middle-aged and older people.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory type of arthritis that can destroy the joint cartilage. RA can occur at any age. RA generally affects both knees.

Post-traumatic Arthritis

Post-traumatic arthritis can develop after an injury to the knee. This type of arthritis is similar to osteoarthritis and may develop years after a fracture, ligament injury, or meniscus tear.

Arthroscopy

Arthroscopy is a surgery that uses the latest technology to look inside a joint, clean it up and to repair any abnormalities that are found. Essentially, there are at least 2 small 1cm cuts. One has the camera and the other is and entrance for the tools that are used. During this procedure lots of water is pumped into the joint to minimize the bleeding and to expand the joint. This also allows us to get a clear picture of what is going on inside the joint.

There are many reasons for needing an arthroscopy. The most common are arthritic changes causing pain and loss of movement, torn cartilage, damaged ligaments and damage to the joint surface. Sometimes we do an arthroscopy to get a biopsy of the joint tissue in order to get a diagnosis on what is affecting the joint.

The most common joints that are investigated and treated in this way are: Shoulder, elbow, wrist, hip, knee and ankle joints.

In my practice I most commonly do knee and ankle scopes.

What is Knee Arthroscopy?

Knee Arthroscopy is a common surgical procedure performed using an arthroscope, a viewing instrument, to consider the knee joint to diagnose or treat a knee problem.

Indications for Knee Arthroscopy

The knee joint is vulnerable to a variety of injuries. The most common knee problems where knee arthroscopy may be recommended for diagnosis and treatment are:

• Torn meniscus
• Torn or damaged cruciate ligament
• Torn pieces of articular cartilage
• Inflamed synovial tissue
• Misalignment of patella
• Baker’s cyst: a fluid filled cyst that develops at the back of the knee due to the accumulation of synovial fluid. It commonly occurs with knee conditions such as meniscal tear, knee arthritis and rheumatoid arthritis.
• Certain fractures of the knee bones

Knee Arthroscopy Procedure

Usually this is done under general anaesthetic but can also be done under spinal anaesthesia. Most of these are done as day cases with admission and discharge from the hospital on the same day.

• 2 small cuts are made on either side of the knee, just below the knee cap.
• Next, a sterile saline solution is injected into the knee to push apart the various internal structures. This provides a clear view and more room to work with.
• An arthroscope, a narrow tube with a tiny video camera on the end, is inserted through one of the incisions to view the knee joint. The structures inside the knee are then visible on a video monitor in the operating room.
• The structures inside the knee joint are examined to assess the cause of the problem.
• Once a diagnosis is made, surgical instruments such as scissors, motorized shavers, or lasers are inserted through another small incision, and the repair is performed based on the diagnosis.

The repair procedure may include any of the following:

• Removal or repair of a torn meniscus
• Reconstruction or repair of a torn cruciate ligament
• Removal of small torn pieces of articular cartilage
• Removal of loose fragments of bones
• Removal of inflamed synovial tissue
• Removal of baker’s cyst
• Realignment of the patella
• Making small holes or microfractures near the damaged cartilage to stimulate cartilage growth
• After the repair, the knee joint is carefully examined for bleeding or any other damage.
• The saline is then drained from the knee joint.
• Finally, the incisions are closed with sutures or steri-strips, and the knee is covered with a sterile dressing.

Postoperative Care Following Knee Arthroscopy

Most patients are discharged the same day after knee arthroscopy. Recovery after the surgery depends on the type of repair procedure performed. Recovery from simple procedures is often fast. However, recovery from complicated procedures takes a little longer. Recovery from knee arthroscopy is much faster than that from an open knee surgery.

Pain medicines are prescribed to manage pain. Crutches or a knee brace may be recommended for several weeks. A rehabilitation program may also be advised for a successful recovery. Therapeutic exercises aim to restore motion and strengthen the muscles of the leg and knee.

Risks and Complications of Knee Arthroscopy

Knee arthroscopy is a safe procedure and complications are very rare. Complications specific to knee arthroscopy include bleeding into the knee joint, infection, knee stiffness, blood clots or continuing knee problems.

Knee Replacement

When is a Total Knee Replacement Necessary?

Usually, when your knee degeneration has advanced to such a point that it is affecting your lifestyle, we recommend that you consider having a knee replacement if you are older than 50 or even younger in certain cases.

The outcome of a Total Knee Replacement

A Total Knee Replacement or Total Knee Arthroplasty (TKA) is a very common procedure and has been modified through the years to give excellent results. Following a Total Knee Replacement, a patient is able to walk long distances usually without pain or discomfort. Patients often return to social sports after TKA.

Should I have a Total or Partial Knee Replacement?

There are very specific criteria for partial or Uni-compartmental knee replacements. If you fulfil those criteria, it is much better to have a uni-compartmental knee replacement as there are less complications, shorter recovery and they tend to do better.

Dr. Endenburg’s Technique

For Total Knee Arthroplasty I use a technique known as “Visionaire”. This requires the patient to have specific x-rays and a limited MRI scan. These scans are then sent to the USA where Smith & Nephew – the supplying company, has engineers that analyse the shape and size of the knee you require. They then manufacture special cutting blocks to match your exact knee. This is like having a computer decide what is best and then we can adjust it according to what we see when we operate.

This technique allows us to work faster and more precisely when operating, reducing your operating theatre time and anaesthetic time. We spend much less time “making the knee fit” and therfore there is greater mobility and less pain post-op.