Anatomy
The knee joint is comprised of the lower end of the thigh bone (femur), the upper end of the shin bone (tibia), and the kneecap (patella). Important structures of the knee joint are outlined below.
Ligaments: These provide strength and stability for the knee. The major ligaments of the knee are:
-The anterior cruciate ligament (ACL): This crosses the knee joint from the back of the end of the femur to the front of the top of the tibia.
- The posterior cruciate ligament (PCL) – This crosses from the under side of the front of the femur to the back of the tibia.
- The patella tendon: This attaches the bottom end of the patella to the front of the tibia.
- The medial (inner side) and lateral (outer side) collateral ligaments: These help prevent sideways movement of the knee.
Meniscus: The two C-shaped menisci of the knee joint lie on top of the tibia. They are the medial (inner side) and lateral (outer side) meniscus. The meniscus is made of a dense cartilage that acts as a shock absorber between the tibia and femur.
Articular cartilage: The ends of the tibia and femur and the back of the patella are covered by articular cartilage. This provides a smooth surface for the bones to move over each other.
Damage to the Knee
Damage to the knee can occur as a result of trauma, or as part of the disease process, e.g. arthritis. The common signs of knee injury or damage are pain, swelling, locking of the joint, or a feeling of the knee giving way. A knee arthroscopy may be recommended to confirm diagnosis of a knee problem, and surgically correct a knee injury.
Operative Treatment
Arthroscopic surgery is performed using a telescope and specifically designed instruments that are inserted through small skin incisions into the knee joint. Following inspection of the knee joint, it is possible to perform a range of surgery, to correct the pathology found. Some common arthroscopic knee procedures are outlined below:
- Lateral or medial meniscectomy: When a meniscal injury has occurred (usually a tear), pain results. If the torn pieces of the meniscus are not removed, further damage could occur to the knee joint. A meniscectomy entails the removal of the torn and damaged pieces of the meniscus.
- Lateral retinacular release: In some patients, the patella does not track properly in its groove as it moves over the femur. This results in pain and damage to the cartilage of the patella. Often, fibrous tissue on the outer side of the patella (the lateral retinaculum) is too tight and pulls the patella to the side, causing maltracking of the patella. A lateral retinacular release is performed to release this tissue to stop it tethering to the patella. A chondroplasty is also performed (reshaping and evening out of the cartilage) if there is damage to the patella cartilage.
- Removal of loose bodies: If a piece of meniscus or cartilage breaks free in the knee joint, it can float around inside the joint, causing pain and possibly further knee damage.
- Defects in the articular cartilage: If the articular cartilage on the femur, tibia or patella is damaged, the knee joint bones don’t move smoothly over each other. Pain and swelling are common symptoms of this. Articular cartilage damage can occur from trauma and is also an early sign of arthritis. A chondroplasty (surgery to the cartilage) is often performed to smooth the cartilage, to help improve knee function and reduce pain. Gross defects in the articular cartilage may be helped by cartilage grafting.
- Anterior Cruciate Ligament (ACL) Reconstruction: A torn ACL cannot heal itself. A reconstruction involves removing the torn ACL and replacing it with a tendon graft harvested from the patella tendon or the hamstring.
Arthroscopic knee surgery is often done as a day procedure. If extensive surgery is performed, it may be necessary to stay in hospital overnight.
Post-operative Course
When you return home, keep your leg elevated and apply ice to the knee joint several times a day for the first few days. It is also important to keep the knee moving – you can do this by sitting on the edge of a table or chair and flexing and extending the knee at regular intervals.
Walking is only for necessity, and should not be considered part of your rehabilitation exercise. Non-weightbearing activities are important in helping your knee recover after surgery. After 2 or 3 days, when your knee is feeling better, gentle mobilisation on an exercise bike is ideal rehabilitation. Start this gently, and increase as your knee allows. Further instructions relevant to your specific surgery will be discussed at your follow-up visits with Dr Mansfield.
Normal recovery following a simple arthroscopy takes about 3 weeks, but will not be complete for up to 6 weeks. It is important to continue the bike riding and other non-weight-bearing exercise for this period of time.
Risks/Complications
This surgery usually has a low complication rate, however complications that can occur include: