What is the cruciate ligament?

There are two cruciate ligaments which cross over each within the knee linking the thigh and shin bones. One of these – the cranial cruciate ligament acts like a brake that stops the tibia sliding forward. It provides stability of the stifle ( knee) joint in the forward plane .

The top ( plateau) of the tibia is sloped slightly and so when the joint is loaded with force ( e.g. standing or walking ) the tibia wants to slide forward – this is referred to as a shearing force . This force is counteracted by the cruciate ligament . When the cruciate ligament is ruptured this shearing force causes the tibia to move forward abnormally when the leg is placed on the ground causing pain in the joint and lameness.

Cruciate ligament failure and arthritis

Rupture of the ligament is usually a consequence of degenerative joint disease sometimes described as a wear and tear arthritis. Sometimes the ligament ruptures as a result of trauma in an otherwise healthy joint. However in most cases there is underlying joint disease /arthritis that may require management in the longterm.

Once the cruciate ligament fails the joint becomes unstable and this movement prevents normal use of the joint and will increase the severity of the arthritis.
Surgical Repair
There are different types of surgery that can be used to treat cruciate rupture ether complete or or partial rupture.
There are two main categories of surgical repair:

  • Extra articular stabilization

    • e.g. Lateral Tibio Fabellar Suture ( LTFS) or imbrication

  • Geometry altering surgery

    • e.g. Tibial Tuberosity advancement ( TTA ) or Tibial plateau Leveling Osteopathy ( TPLO )

We will describe here one technique from each of the two major categories of surgery .

1. Extra articular stabilization – with a prosthetic ligament

This technique involves placing a prosthetic ligament anchored behind the joint and threading forward to a bone tunnel made in the top of the tibia. This new artificial ligament runs parallel to the original cruciate ligament but is outside the joint .This technique is usually carried out in small dogs and cats .

fig1 .

2. Geometry altering surgeries : eg TTA

There are two procedures which alter the mechanics of the joint in a way that reduce the shearing force towards zero and so removes the need for a cruciate alignment function.

The first such technique described was called TPLO and the newer technique which we do is called TTA .

The TPLO procedure involves cutting and rotating the tibial plateau to remove the slope and therefore remove the shearing/sliding force. The tibial plateau is re attached with a special plate .

TPLO moves the tibial plateau to meet the force.

The TTA procedure advances the patellar tendon forward which changes the angle between this tendon and the tibial plateau to 90 degrees which also reduces the shearing force towards zero .

This is achieved by cutting the non weight bearing part of the tibia bone and advancing this front portion of the tibia and holding it in place with a special plate and placing a bone graft in the gap .

TTA moves the joint force to meet the tibial plateau

Winola 6 y old Labrador

We offer both extra articular stabilization by means of a prosthetic ligament and also geometry altering surgery using the TTA technique .

In general the Prosthetic ligament is very suitable for smaller patients and the TTA for larger patients . However the choice of surgery depends on several factors which we discuss individually in every case so that as an owner you can make an informed choice.

As in all orthopaedic surgies there is a small risk of complications which we can discuss .

Your pet will first need x rays ( this may have already taken place ) under a short aneshetic in order to allow evaulation annd pre operative planning after which we will disicuss which surgical option is appropariate for your pet and schedule the surgery . On the day of surgery you need to withold food from 9pm the night before and withdraw water at 7 am and admit your pet to us at 8.30 am . The procedure takes 2 to 3 hours will speak with you during the day to report. In the case of TTA surgery your pet woudl normally go home the following day .


Post operative care and rehabilitation

During the first 12- 24 hours at home your pet will feel quite drowsy from the pain control medications. In addition there will be a large bandage on the limb which will make getting up a little awkward. Some assistance getting outside to to the toilet will be needed.

However very quickly within a day or so patients feel much better and quickly get used to getting up and around by themselves.

It is important for the first three weeks to restrict activity to toilet visit to the garden .

During the next 3 weeks you can allow your pet to stay out in the garden for 10 minutes at a time for up to five times daily.

Restricted controlled lead walking can start from 6 weeks.


garden only

lead walks

1 , 2 , 3

toilet only


4 , 5 , 6

10 min 3-5 times daily


6 – 10

5 minutes twice daily


10 minutes twice daily


15 minutes twice daily


20 minutes twice daily


25 minutes twice daily

* exercise advice may be modified according to each individuals progress and needs.

Medication :

Your pet will be going home on medication . This varies from case to case but will include pain control medicines and anti inflamatories. The type of medication and amounts are tailored to each patients needs. Usually medication reduces after the first two weeks but It is common to need anti inflamatories for the first two to three months

Arthritis and weight control

Most pets with cruciate ligament rupture also have arthritis and so this will require on going monitoring and management . This includes a balance of weight control, exercise and arthritis medications. Again this is tailored to each patients specific needs.

Check ups :

We will schedule regular check ups after the operation .If you are worried in between check ups please don’t hesitate to call for advice. 01 2821909.