Menisci can be torn by shearing forces of rotation applied to the knee during sharp and rapid motions, especially in sports demanding quick-reaction body movements. Incidence increases with age and degeneration of the underlying cartilage. More than one tear can be present in an individual meniscus. Patients with meniscal tears may have rapid onset of a popping sensation during a certain activity or knee movement.

Patients may experience pain in the knee's interior or exterior during activities. Some patients also experience 'locking', which is a sensation of a 'jammed' knee unable to straighten fully.

Occasionally, this injury is associated with swelling and a warm sensation in the knee, often associated with locking or an unstable sensation in the joint. The surgeon can perform certain manoeuvres while examining the knee which may help detect meniscal tears.

Routine X-rays may not reveal meniscal tears but can be used to exclude other problems of the knee joint. 

• 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 radiology 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 radiology 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.

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 activities. 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. 

A ligament injury to the knee is usually painful at rest and may be swollen and warm. The pain usually worsens if one bends, puts weight on the knee or walks. The severity of the injury can vary from mild (minor stretching or tearing of the ligament fibres, such as a low grade sprain) to severe (complete tear of the ligament fibres). Patients can have more than one area injured in a single traumatic event.

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 can 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.