• Osteoarthitis
  
  • This is most often due to wear-and-tear of the knee joint, and is associated with age and activity levels. It can also be due to previous injuries of the knee as well as pre-existing malformations. Osteoarthritis most often affects individuals over the age of 50, but with increasing active lifestyles, even younger people can be affected. In the early stages, the condition can be treated by activity modification, medications and other non-surgical means. However, in more severe cases, surgery may offer the best chance of long-lasting results, and this may range from simple procedures such as arthroscopy, to more complex operations such as realignment surgeries and knee replacement.
    

• Rheumatoid and other inflammatory arthritis  
  
  This group of diseases include rheumatoid, sero-negative arthritis, systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), psoriatic arthritis and other rare forms of arthritis. They are often autoimmune in nature, and the disease process can often be suppressed by medications, but not usually cured. If joints become irreversibly damaged by the disease, joint replacement is often a good option that can yield excellent results.
  
  
  
• Gout and other crystal diseases  
  These conditions are caused by the presence of various types of crystals within joints. Uric acid crystals give rise to gout, while calcium pyrophosphate crystals cause pseudogout. The crystals are responsible for pain, swelling and inflammation of joints, including the knee, ankle and foot joints. Medications can often control the acute attacks, and dietary measures may help. In severely affected knee joints, total knee replacement can often give long-lasting relief.
  

Trauma can result in injuries to the ligaments situated on the inner (medial collateral ligament) or outer (lateral collateral ligament) portions of the knee, as well as within the knee itself (cruciate ligaments). Immediate pain is a common manifestation of such injuries, although pinpointing the exact location can sometimes be challenging.

Usually, a collateral ligament injury is felt on the inner or outer portions of the knee. A collateral ligament injury is often associated with local tenderness over the area of the ligament involved. 

A cruciate ligament injury is felt deep within the knee. It is sometimes noticed with a "popping" sensation with the initial trauma. The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee, especially in sports such as basketball and football. The ACL stabilises the knee for cutting, twisting and jumping and pivoting activity. The anterior cruciate ligament is in the centre of the knee joint. When you tear an ACL, you will often feel or hear a pop, feel the knee shift out of place and develop significant swelling in just a few hours. 

Ligament injuries to the knee are typically painful at rest, accompanied by swelling and warmth. Pain intensifies when bending the knee, putting weight on it, or walking. The severity can range from mild (minor stretching or tearing of ligament fibres, such as a low-grade sprain) to severe (complete tear of ligament fibres). In some cases, a single traumatic event may result in injuries to multiple areas.

Ligament injuries are initially treated with ice packs and immobilisation, with rest and elevation. We generally recommend that patients avoid bearing weight on the injured joint, and use crutches for walking, if necessary. Some patients are placed in splints or braces to immobilise the joint to reduce the pain and promote healing. Arthroscopic or open surgery may be necessary to repair severe injuries.

Surgical repair of ligaments may involve suturing alone, grafting, and synthetic graft repair. These procedures can be done by either open knee surgery or arthroscopic surgery. The type of surgery depends on the level of damage to the ligaments and the activity expectations of the patient. Many repairs can now be done arthroscopically. However, certain severe injuries will require an open surgical repair. Reconstruction procedures for cruciate ligaments are increasingly successful with current surgical techniques.

• Arthroscopy—A surgical technique where a small diameter video camera is inserted through tiny incisions on the sides of the knee to examine and repair internal knee joint problems. Tiny instruments can be used during arthroscopy to repair the torn meniscus.
• Arthrography—A radiological technique where a contrast liquid is directly injected into the knee joint and internal structures of the knee joint so that they become visible on X-ray film. It is not used commonly used nowadays as MRI is getting more popular.MRI scan—A radiological technique where magnetic fields and a computer combine to produce two- or three-dimensional images of the internal structures of the body. It does not use X-rays and can give accurate information about the internal structures of the knee when considering a surgical intervention. Meniscal tears are often visible using an MRI scanner.
• Once diagnosed, meniscal tears are generally repaired arthroscopically.

The surgical treatment options vary according to the different conditions. Common knee surgeries include:

Diagnostic and therapeutic arthroscopies

This procedure, typically conducted as a day surgery, involves the use of a small telescope inserted into the knee. Arthroscopy is commonly employed for patients with meniscal and cruciate ligament injuries. Patients can return home either on the same day or the following day. Younger patients with isolated cartilage injuries may be offered a two-stage articular cartilage transplantation.

Open surgeries

These surgeries address various knee issues, including proximal and distal realignment procedures for isolated patellofemoral problems. Techniques involve lateral retinacular release of the patella and tibial tubercle elevation and medialization to enhance patellar tracking. 

High tibial osteotomies which involve cutting bone, are frequently performed procedures. They include either a medial opening wedge or lateral closing wedge osteotomy of the proximal tibia. The aim is to redirect weight-bearing forces from the medial compartment of the knee to the lateral side, alleviating pain and correcting varus deformities. Bilateral procedures can be done in a single session or in a staged manner.  

Total knee replacement

This procedure is commonly performed for severe tricompartmental arthritis. It entails resurfacing the damaged articular lining of the knee, mainly the distal femur and proximal tibia, with metal prostheses. A tibial articular liner/insert made of high-density polyethylene is inserted, and the patellar articular surface may also be replaced with a patellar button, depending on the surgeon's findings.

The prosthesis is usually fixed with bone cement. If only one compartment is involved, unicompartmental knee replacements are offered. The risks of this elective surgery is weighed against the benefits of this procedure as it improves the quality of life of most patients and gives them significant relief from pain. 

The commonly cited risks are of that related to anaesthesia, bleeding, infection, deep venous thrombosis in the veins of the lower limbs, fracture, loosening of the prosthesis- aseptic or septic. 

Patients are usually assessed preoperatively by anaesthetists and if deemed fit, they can arrive on the day of surgery. Postoperatively, a drain is usually placed in the knee, removed on postoperative day 1 or 2, and followed by the patient sitting up, getting out of bed, and walking with full weight-bearing on the operated limb using a walking frame. Typically, patients can return home by the 4^th or 5^th postoperative day.