The knee joint is composed of the top of the tibia (shin bone) and the bottom of the femur (thigh bone). The patella (kneecap) is also an integral part of the knee joint. Where these three bones contact each other there is a layer of very smooth articular cartilage lining.
These bones are held together by ligaments. Ligaments essentially function as living pieces of rope. They prevent the movement of the bones in relation to one another.
Major Knee Ligaments
The major ligaments of the knee are:
- Anterior Cruciate Ligament (ACL)
- Posterior Cruciate Ligament (PCL)
- The Medial Ligament (MCL)
- The Lateral Ligament (LCL)
- The Medial Patellofemoral Ligament (MPFL)
Anterior Cruciate Ligament (ACL)
The anterior cruciate ligament is a strong band of tissue that sits in the centre of the knee next to the PCL. It is very important in preventing rotation of the knee. The ACL is commonly injured during sport. This may occur with contact injuries or more commonly with non contact twisting injuries. Tearing of the ACL often leaves the knee feeling unstable. A torn ACL will usually prevent most high level sporting activity and occasionally even low level activity will be difficult. A reconstruction of the ACL may be required and usually gives good results.
Posterior Cruciate Ligament (PCL)
The posterior cruciate ligament is a strong band of tissue that sits in the centre of the knee next to the ACL. The PCL is usually injured in high energy contact injuries. Instability after
PCL injury is rare. Tearing of the PCL can usually be treated with intensive physiotherapy over a long period of time. Occasionally PCL reconstruction is required.
The Medial Ligament (MCL)
The medial ligament is a strong band of tissue on the inside of the knee. It helps prevent side to side movement of the knee. The medial ligament is usually injured in contact injuries to the knee. Injuries to the medial ligament can usually be treated with a combination of a knee brace and physiotherapy. Occasionally MCL reconstruction surgery is required.
The Lateral ligament (LCL)
The lateral ligament is a strong band of tissue on the outside of the knee. Along with several other structures on the outside of the knee, it helps prevent side to side movement of the knee.
The lateral ligament is rarely injured. When injury does occur multiple other structures are often involved. When injured the lateral ligament will often require surgery to correct instability.
The Medial Patellofemoral Ligament (MPFL)
The MPFL is a relatively slender band of tissue attached to the medial (inside) edge of the patella. If the patella is dislocated this structure often tears. Surgery may be required.
More information on ACL reconstruction and dislocation of the patella can be found in the procedures section of this website