Anterior Cruciate Ligament (ACL) Ruptures

Along with the bone, the hyaline cartilage, the synovium, the capsule and the menisci, the joint also has two special ligaments within.  These are called the “cruciate ligaments”.  There is an anterior cruciate (at the front) and a posterior cruciate (at the back).  The term “cruciate” comes from “cross” in Latin and refers to the fact that the anterior cruciate ligament runs upwards and backwards and the posterior cruciate ligament runs upwards and forwards.  They cross in the middle of the knee as you would note on a crucifix.  Thus the name.

These ligaments are very important.  They provide a large part of the stability enjoyed by a knee joint.  They are responsible for limiting and controlling forwards and backwards movement of the shin bone on the thigh bone, and also rotary movement of the shin bone on the thigh bone.

If the anterior cruciate ligament is ruptured, patients often feel quite unstable whilst loading bearing on the knee.  This can occur with normal walking but is also exacerbated by ascending and descending steps or slopes, running and squatting.  Changing direction, weaving or cutting whilst running is particularly troublesome for patients without an anterior cruciate ligament.  Ask any touch football player!

These ligaments can be ruptured with traumatic events.  We not infrequently see them with netballers, softballers, footballers and baseballers.

The anterior cruciate ligament has a very rich blood supply.  If it is ruptured, the vessels are also damaged.  The knee joint rapidly fills with blood.  It becomes tense and very painful within a few hours.

The Orthopaedic Surgeon can usually make the diagnosis based on the history alone.  A clinical examination further aids the diagnostic process and ultimately, an MRI scan examination can sometimes be performed.