Knee Information
Knee
Joint
The knee joint
consists of the lower end of the femur bone, or thigh bone, resting on the upper end of the
tibia, or shin bone, with the patella or knee cap, at the front. Ligaments or fibrous
connective tissue, attach these bones to provide stability. The main ligaments
are the anterior and posterior cruciates, and the medial and lateral
collaterals.
The
knee also contains medial and lateral menisci, which are crescent-shaped discs
of cartilage that work to cushion or absorb weight between the ends of the bones
in the knee joint, and provide stability. As the body ages these cartilages become more brittle and susceptible to tears.
The surfaces of the knee bones are covered by articular cartilage
which is normally smooth tissue, allowing the bones to glide easily on each
other. A capsule surrounds the knee joint which produces synovial fluid or
lubricant into the joint to reduce friction.The knee joint acts like a modified hinge, that not only flexes and extends, it also has a complex rotational component, and is one of the body's major weight bearing joints.
The knee joint is vunerable to injury which can occur through twisting movements, sudden stopping and starting, or changes in direction. The knee is also susceptible to degenerative changes of the cartilage associated with arthritis.
Knee Conditions
What is a Meniscal or Cartilage Tear?
A tear to the medial or lateral meniscus is usually caused by a twisting injury, causing pain on the inner or outer side of the knee, with some joint swelling. Occasionally the joint will feel as if it is locked or a catching sensation localized to the side of the knee, with tenderness and swelling, if the torn segment becomes caught between the bones. If untreated, long term irritaton and damage can occur leading to osteoarthritis. Damage to the articular surface cartilage decreases shock absorption capability and increases friction in the knee joint. Floating fragments of cartilage can also cause the knee joint to lock, and damage the smooth joint surfaces leading to osteoarthritis if untreated.
What is a Cruciate Tear?
A rupture of the anterior or posterior cruciate ligament can occur with abnormal twisting of the knee, causing the ligament to overstretch and tear. This often requires surgical repair as it causes knee instability. An anterior cruciate ligament (ACL) injury is a relatively common sporting injury, especially with high impact twisting sports such as netball and football. Generally there is an injury where the knee gives way with a lot of pain and swelling, and may initially settle with physiotherapy, but continue to feel weak and unreliable on return to sport. An MRI will provide a definitive diagnosis, but generally operative reconstruction is the most appropriate option to enable continued sporting activities. Specialised physiotherapy and recovery for up to 9 to 12 months may be necessary, to allow and develop strengthening of the graft before a safe return to sport, and minimise re-injury.
What is Mal-Tracking?
Mal-tracking of the patella or knee cap is generally caused by structural abnormalities of the patella stabilizing mechanisms. The commonest form is when the knee cap moves laterally or to the outside of the knee when flexing or bending the knee. This can be treated by surgical lateral release.
What is a Knee Cyst?
Popliteal or
Bakers cysts are fluid filled sacs which may develop behind the knee. These are relatively common and not noticeable unless they have enough fluid to cause symptons. It may cause problems if the cyst becomes swollen with fluid and quite large, with a definite lump. The fluid is usually due to a problem within the knee joint such as torn menisci, worn articular cartilage, or arthritis. If these conditions are treated the cysts usually reduce, and only require specific surgery if they continue to cause symptoms. Occasionally, the cyst can leak fluid into the calf causing swelling, tightness and pain. An ultrasound scan may be recommended to assist diagnosis.
What is Knee Osteoarthritis?
Knee
osteoarthritis, is a degenerative joint disease or progressive disorder, caused
by gradual deterioration or loss of the cartilage of
the
shock absorber layer of the joint.
As the cartilage is worn away, the bone forms spurs or areas of abnormal hardening, and fluid-filled pockets in the marrow known as subchondral cysts. As the disorder progresses, pain results from deformation of the bones and fluid accumulation in the joints. The knee joint becomes painful or aching with weight bearing or activity such as walking. The knee is often swollen, and eventually may be deformed in shape, which is visible on xray. As part of the aging process, the joint chondral layer becomes brittle and more susceptible to wear and injury. Knee osteoarthritis may also occur as a result of previous joint trauma, ligament instability, or abnormal stresses to the joint. People who are overweight are at a much higher risk of rapid worsening of knee arthritis. Depending on the type and severity of your symptoms, the type of surgery required may vary from arthroscopic surgery, osteotomy, unicompartmental knee replacement, or total knee replacement.
Knee Arthroscopy
What is Knee Arthroscopy?
A knee arthroscopy is a relatively routine procedure
that orthopaedic surgeons use to examine and treat the inside of the knee joint.
It is a minimally invasive surgical procedure whereby a small telescope is
inserted into the knee joint and the inside of the joint is then viewable on a
video monitor. Knee arthroscopy allows the surgeon to safely and accurately
examine, diagnose and assess damage to the joint, and to perform corrective
procedures. Generally two small incisions, about 0.5 cm long, are made to insert
the arthroscope and the instruments required to perform the surgery. The
incisions are much smaller than with open surgery, which assists faster healing,
causes less trauma, and lowers the risk of complications. Some knee conditions
which may be diagnosed and treated by arthroscopy surgery include repair of torn
menisci, removal of loose bodies or loose pieces of cartilage, resection of
inflamed osteoarthritic knee segments, reconstruction of a rupured anterior
cruciate ligament, repair or resection of torn cartilage, repair of torn
ligaments, patella mal-tracking and bakers cysts. Knee arthroscopy surgery is
usually performed as a day procedure, under a general anaesthetic.
Knee Replacement
What is Knee Replacement?
Total knee replacement or arthroplasty surgery, replaces the damaged and diseased parts of the knee joint with specially designed artificial implants or prostheses. The entire knee joint is not actually replaced, but the damaged bone and cartilage at the ends of the joint bones are resurfaced. The resurfacing components are designed to recreate the natural contours of healthy knee bones. These metal and polyethylene implants allow the bones to glide smoothly similar to natural cartilage, and generally consist of four components. The tibia prosthesis has two elements, including a metal tray attached to the tibial bone, and a plastic insert which provides the bearing surface. The femoral component replaces the distal end of the thigh bone and also replaces the groove in which the patella fits. The patellar component replaces the surface of the knee cap which protects the knee joint, and slides across the front of the femur. In some case it is not necessary to resurface the patella. The main aim of total knee replacement surgery is to provide pain relief, help restore daily living activities, and improve knee function and mobility. A recent technological advancement with knee replacement surgery is the Signature Personalized patient system which utilizes an MRI scan to create individual positioning guides. These pre-operative custom made femoral and tibial guides developed from the patients MRI, create a three-dimensional joint reconstruction, enabling the surgeon to provide a more specific personalized knee replacement.
What is Revision Knee Replacement?
Revision knee replacement means that part, or all of the original primary knee replacement implants need to be revised or replaced, and so this procedure varies greatly for each person. Revision total knee surgery is often more complex due to the reduced amount of natural bone, and is performed when the primary total knee replacement prosthesis has worn out, or loosened in the bone. Revisions may also be performed due to recurrent dislocation or instability, trauma such as a fall, infection, or rarely because of ongoing pain or leg length discrepancy.
