Cruciate ligament surgery

Normal versus torn cruciate ligament

Injuries to the cranial cruciate ligament in dogs are extremely common, especially in large active breeds. The cranial cruciate ligament (what in humans is called an ACL) prevents the lower half of the leg from displacing forwards when the dog or cat puts weight on the leg. If the ligament snaps, the joint becomes severely unstable, leading to rapid progression of arthritis and damage to the cartilages in the joint.

The majority of dogs who rupture this ligament do so because of degenerative disease in the joint weakening the ligament over a period of months or years. The trauma involved in the final rupture can be very minor. This is an extremely important point to be aware of when deciding how to treat the injury.

It is best to think of a cruciate injury as a surgical problem. The ligament never heals once it starts to degenerate, it just degenerates further until it finally snaps. Snapped cruciate ligaments never heal. The blood supply to ligaments is extremely poor, and the torn ligament cannot be sutured together again.

Surgery involves two parts. Firstly, the joint is opened and any torn ligament or cartilage is carefully removed. Secondly, the joint needs surgery to stabilise it now there is no cranial cruciate ligament.

There are essentially two ways of doing this. The more basic technique involves placing a restrictive band of some form that attempts to replace the function of the lost ligament. The more complex techniques involve changing the structure of the bones to alter the forces acting on the joint.


TPLO surgery

Surgical planning

It is important to realise that orthopaedic surgery is complex, and requires a high level of planning to choose the right procedure. There is no one-size-fits-all option for cruciate surgery, the best option should be chosen after detailed examination, x-ray imaging, and discussion with the patient’s owner.

Tibial surgery

This group of surgeries involves making various cuts to the tibia (shinbone), and then securing it with a bone plate and screws. This results in the forces previously resisted by the cruciate ligament either being neutralised or transferred to another anatomical structure.

Return to normal function after surgery can be dramatically faster than with the traditional nylon band technique.

There are multiple versions of these advanced procedures. They include the TPLO, TTO, and TTA.

TPLO (Tibial Plateau Levelling Osteotomy)

TPLO procedure

This is the most successful technique in terms of normalising forces around the joint and has statistically the best long term outcomes. We are now able to offer this surgery for dogs of almost any size, including small breeds.

The surgery involves making a single, curved cut in the tibia, then rotating the joint surface around a set number of degrees, and finally stabilising it with a bone plate and screws. The result is that the force which pushes the lower limb forwards when the animal bears weight is removed, eliminating abnormal strain on the joint.

TPLO is an operation with a long history of success in many countries. This is the “gold standard” surgery in specialist practices around the world for cruciate ligament injury. If the joint is suitable for this procedure, and if finances permit, this would be our recommended first choice surgery where possible.


TTA Surgery

TTA (Tibial Tuberosity Advancement)

The TTA procedure is technically the simplest to perform, and comes in a variety of forms, depending on what plating system is used and what spacer is placed in the cut bone. The result is the stabilising action of the cruciate ligament is replaced by the strain being transferred to the patellar tendon instead.

TTA is a good technique for medium to large breed dogs. It cannot be done if the tibial plateau angle (measured on pre-operative x-rays) is too high. This is why it is essential to have proper x-rays of the limb performed before deciding which procedure is best suited to your dog.

There are some concerns about risks with TTA, including a higher rate of post-surgical cartilage injury, risk of patellar tendinosis due to the added stress placed on it, and real problems dealing with any post-operative infection that might develop.

Studies comparing TPLO with TTA consistently have the TPLO producing better results for the patient.

TTO Surgery

TTO (Triple Tibial Osteotomy)

This is a procedure that involves three cuts in the tibia. It combines features of the TPLO and the TTA, but functions more like a TTA than a TPLO. TTO is a very versatile procedure, that can cope with severe tibial plateau angles, and can be adapted to manage patellar luxation at the same time relatively easily.

Extrascapular nylon procedure

Extracapsular surgery

This includes what was traditionally the most popular surgery, where a single or double strand of nylon leader line or Fiberwire is placed to try and replace the function of the original cruciate ligament. This can result in good function, but the larger the patient the less satisfactory the results tend to be. The implant is not physiological, in that it does not properly replace the original ligament, and can lead to a rapid progression of arthritis in the joint. Recovery times from surgery can be prolonged. This is a fair option for small dogs, not very good for medium dogs, and not good at all for large dogs.

This technique is simple to perform and avoids the risk associated with cutting bone for the TPLO. However, the nylon will stretch in time and ongoing support is dependent on periarticular fibrosis rather than the removal of the abnormal movement which the TPLO achieve. Additionally, while this technique is most commonly performed on small breeds of dog, these breeds very frequently have extremely steep tibial plateau angles, which makes them poor candidates for extracapsular surgery, since this technique struggles to work when the slope is steep.

Before and after cruciate surgery

Our recommendation for managing cruciate injury in dogs is:

  • TPLO is the best surgery available and should be the first option if the bone shape permits, and if finances are available
  • TTA is a secondary choice, still a good option but not as good as the TPLO. Reduced price is the main reason for choosing this option
  • TTO is chosen if the tibial plateau angle is too steep for TPLO or TTA
  • Extracapsular surgery is a cheaper option for small breed dogs, but is significantly less successful than the TPLO
  • Dogs that have had a previous extracapsular nylon surgery with unsatisfactory results, can have a TPLO as a revisional procedure.

We have lots of dogs now who have had both knees operated on and returned to running and working. A dog who ruptures both cruciate ligaments can have the joints operated on relatively close together, which dramatically reduces recovery time.


The period of rest after cruciate ligament surgery is quite long, up to 12 weeks. It is critically important that the instructions given are followed closely in order to get the best results. We have a rehabilitation programme for you to follow during this period.


The price range for TPLO surgery is from $4500-5500, depending on patient size. The only charge for revisits is for any additional dressings or medications used, and for sedation and x-ray at 6 weeks. Note that there are normally no additional dressings or medications required at all. The 6-week xray costs $300-350 depending on patient size. We can guide what to look for in post-op revisits if required for those having the checkups done locally.

How to book

Give Customer Services a call on 09 238 7486 or email: to discuss the transfer of your patient to our clinic for assessment and treatment. You may be asked to bring any clinical notes, x-rays images, and medications with you when you come.

Dr Paul Eason BVM&S MANZCVS (Surgery; Emergency & Critical Care Medicine)

Check out Riley 12 days post TPLO op


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