The New Ridgestop Solution.

Probably second only to cruciate failure, luxating patella issues are a frequent cause of lameness in dogs and sometimes cats too.

This article represents the personal opinion of Alistair Marks MRCVS, at the time of writing. It is offered, as information, as might be presented in the consulting room and not a scientific document and if you are not a client, no liability for acting on any information written here is accepted. It is not intended to replace your consultation with your own veterinary surgeon but it may help in discussing the various options available to you should your pet require management for a luxating patella.

Anatomy and function.
The stifle joint is equivalent to the knee, in ourselves. It is a joint between the femur (thigh bone) and the tibia (shin bone). Although primarily functioning as a hinge, it is much more complex in that as well as flexing and extension, the stifle can rotate (twist) as well, to a degree

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There is a third important bone, the patella or kneecap. It is actually situated within the output tendon of the large quadriceps femoris (quads) muscles in the front of the thigh. The underside of the patella is covered in hyaline (joint) cartilage and runs in a groove also covered in hyaline cartilage on the front of the lower end of the femur. This apparatus allows the quadriceps tendon to curve around the end of the femur and attach to and straighten the tibia at all positions of the stifle. The cartilage should provide an almost frictionless gliding action that allows a lifetime of free movement.

What happens when the patella luxates.
If the patella is not in the groove, the action of the quadriceps no longer straightens the stifle properly leading to lameness and over time the cartilage on the underside of the patella and that on the groove can become buffed away leading to arthritis leading to pain and stiffness.

Why does it happen.
Occasionally, it is truly traumatic, like a road traffic accident and a normal stifle is sufficiently disrupted to tear the tissues that retain the patella in place, often associated with an injury to the cruciate ligament.  These patients need a repair appropriate to their injury.

Much more commonly the luxating patella arises spontaneously or occurs during activities well within what might be considered the “rough and tumble” of normal life.

In cats and small to medium dogs, the patella generally ends up on the inside, in large breed dogs on the outside.

In order that the severity of the problem can be compared between patients, there is a grading system and fortunately with each grade, there tends to be fewer patients.

In a grade 1, the patella can be luxated by pressing it with the fingers but spontaneously drops back into place when released. Many cats and small dogs with unstable Grade 1 patellas have no symptoms and the condition remains un-diagnosed or is picked up as an incidental finding. I presume they learn how to tense their muscles and control their feet position to keep the patella running correctly in the groove. However, some do have painful episodes and over time become lame as the cartillage on the underside of the patella and the affected side of the groove wears away, leading to arthritis.

In a grade 2, the patella luxates easily when the stifle is flexed and stays out until manually relocated or the animal extends their leg and rotates their stifle to put it back in place. These patients have episodes of lameness which can be both very painful and distressing to the animal. Sometimes the animals work out how to relocate their own patella and in the early stages are pain free in between episodes. However, the concern is that the wearing aways of the cartilage, as the patella flips in and out, will lead to constant lameness due to arthritis.

In a grade 3, the patella is actually out of position most of the time but the patella can be relocated into the grove but re-luxates when the animal extends or flexes the joint. These animals are usually constantly disabled and as the problem is often on both legs, they have to take more of their weight on their front legs and bunny hop with the back legs. In smaller breeds there is often a bow legged appearance, larger dogs tend to be knock kneed.

In a grade 4, the patella is permanently luxated and cannot be replaced. Often the groove is very shallow or flat and over time the quadriceps become permanently shortened and the stifle is kept flexed. Like the grade 3s but more so, these unfortunate animals are profoundly disabled. Animals in this group are beyond simple surgery and often require complex and individually planned re-alignment surgery and this is outwith the scope of this article.


What are the symptoms and what can be done to improve the situation?
Occasionally for symptomatic Grade 1 and some Grade 2 patients. tightening the joint capsule on the side opposite to the luxation is sufficient to maintain the patella in the right place for sufficient time for the animal to learn how to keep their patella in the right place, themselves but this simple surgery should be viewed as potentially a temporary solution, unless the luxation has arisen from trauma as the soft tissues will slacken in a few weeks and this may allow the problem to recur. However doing this surgery does not stop a more involved procedure being performed in the future, if it turns out to be unsuccessful.


For most, altering the bony structures of the joint is required.
In normal animals the patella largely stays in place as there is a deep groove capturing about half of the patella in cross section.

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Most animals with a luxating patella have a more shallow grooves and this allows the patella to ride up onto the edge of the groove and then luxate. Sometimes a sudden worsening of the symptoms occurs in an longstanding mild case and this can be when the cartillage covering the edge of the groove is knocked off, meaning the effective edge is lowered making it easier for the patella to luxate.

Doing something to deepen the groove will provide better stability for the patella.
There are two established surgeries for this, one depicted as VRS 1 VRS 2 and VRS 3 in my very simplified diagram of the cross section of the groove and patella. For my illustration, the patella is luxating to the left. The VRS stands for V recession sulcoplasty and what happens in this surgery is that a V section of bone and cartilage is cut from the groove and set to one side. This is shown as pink. Once removed and carefully set aside, a second (green) wafer of bone is removed and discarded. The original (pink) piece of bone is placed back into the now deepened “V” which means more of the patella is “captured”.


The patella now runs in a new deeper grove and most of the pressure is taken by the preserved cartilage of the (pink) triangle, with the sides healing with scar or fibrocartillage. However, things are never this simple and the fit is good but not exact and therefore there is no escaping that the cartilage is not optimal after the surgery. Unfortunately, sometimes there is no groove the area being flat or sometimes even convex in the high grades. With those stifles a new groove has to be fashioned in the femur with a round rasp. Sadly this removes all of the cartilage and relies upon scar cartilage forming in the longer term.

The Ridgestop.
This is an exciting and relatively new implant that takes a different view and instead of deepening the groove, it builds up the rim of the groove on the side on which the patella is luxating. The implant is a tough polymer, the same sort of material from which the cup of some hip replacements is made and is a precision made three dimensional structure which is screwed onto the side of the groove. The effect is the same, that is to capture more of the thickness of the patella and stop it going over the implant and luxating.

The original groove is not touched and therefore it would seem likely that the long term health of the cartilage in this area will be better.

There is a concern as to whether the implant will wear and there have yet to be implants in patients, for the whole of life but I don’t believe there has been issues with the earliest cases. Whilst it is true both dogs and people can wear out the polymer cup of a replacement hip, the polymer in those cases is bearing the entire weight of the patient, whereas in a Ridgestop procedure the patella is guiding the patella without carrying weight directly.

There are Ridgetop implants for most patients from mid terrier size and above.

If you would like to see a diagramatic animation of the Ridsgstop Procedure see our video below

If you would like to see an actual Risdestop surgery, by the main developer of the tecnique, click here but be aware this is real surgery, on a real leg with real blood!

Moving the tibial tuberosity.
If you sit on a table, so that your feet are off the ground and your knees are bent at ninety degrees, you can rotate your feet in and out and feel your patellar ligament and the bony insertion on the front top of your tibia (shin) moving inward and outward in relation to your own patella

In traditional surgery, often the bony insertion of the patellar ligament, the tibial tuberosity, is moved in the opposite direction from the luxation to alter the angle of pull of the quadriceps mechanism to make the deepening of the groove surgery more reliable at the time of surgery, increasing the chances of good long term stability.

There is little doubt in the higher grade luxations that undoing a rotational deformity of the tibial tuberosity can be needed but in the milder case, it can be argued that the tibia is actually alright and it is the tendency to allow rotation of the tibia and foot that is either contributory to, or is a consequence of the luxation.

What has been found with the Ridgestop in the lower grade luxations is that it provides such immediate resistance to luxation that the lower leg tends to straighten out, spontaneously, without surgery to the tibia.


What happens on the day of the operation.
Whether your pet is having conventional surgery or a Ridgestop, he or she would be admitted early in the morning and settled into one of our day kennels in the prep room.

Prior to the administration of the anaesthetic, we shall weigh and re-examine your pet and if it has not been done already, take a pre anaesthetic blood sample. The practice has a modern blood analyser for this purpose and results are available within 15 minutes, allowing any adjustments to be made in the anaesthetic protocol.

As both procedures are significant operations we provide intravenous fluid support (a drip) for all our luxating patella patients.

It is the routine at Oak Tree Vet Centre that patients receive not only a sedative to allay any fear but two analgesics (painkillers) as their premedication before general anaesthesia.

Following induction of anaesthesia, all patients are intubated to protect their airway and maintained via a modern gas anaesthetic system featuring sevoflurane, the latest and considered the best anaesthetic gas. At this time an intravenous antibiotic is given to reduce the risk of infection.

All anaesthetised patients are monitored throughout, by the theatre nurse under the constant supervision of the operating surgeon. The leg is shaved and vacuumed to remove all hair. The skin is then washed and disinfected by a three stage cleansing program.

All patients have, of course, their own set of operating drapes and instruments. We have surgical power tools from human surgery that are autoclaved along with the specialised instruments that are needed for these procedures.

The patient is draped with large cloths and the foot recovered in a sterile bandage.

The procedure begins the primary veterinary surgeon and a scrubbed assistant, whilst a veterinary nurse monitors the anaesthetic and a fourth person is available to meet the surgeon’s equipment needs throughout the operation.

At the end of the procedure, before leaving the theatre, the wound is cleansed with sterile saline, dried and a spray bandage applied. On top of this a sterile bandage like a giant elastoplast is stuck.

We don’t use a bandage so that the patient has mobility right from immediately post op.

For dogs undergoing a Rdgestop, a post op x-ray is done to check that the screws are correctly placed and of the correct length.

All patients receive post operative pain relief for as long as is required for them to recover from surgery.

We now offer therapeutic laser therapy at the time of surgery to reduce post operative discomfort and swelling. We were the first in Scotland and one of the first few practices, in the UK to have a Class IV laser.


Post operative care
On collecting your pet, both the surgeon and a veterinary nurse will go through what has been found and done and give you written instruction to help you manage the initial recovery.

We like to check all of our luxating patella patients after three days. With both methods, we remove the stitches after 10 days.

With the conventional surgery, it is imperative that the stifle is carefully cared for with minimal movement, toilet exercise on a lead and no jumping, stairs or playing for the first four weeks and then a gradual increase in lead exercise.

With the Ridgestop, your dog is allowed a few minutes lead walking several times a day right from day one, a big advantage for boisterous individuals. Initially on a lead and then onto an extending lead for the first four weeks.

At this time, we hope to start active rehabilitation, if that is required. We believe, in the case of medium and larger dogs, the best rehabilitation is hydrotherapy and the equipment of choice is the water treadmill. Twice a week sessions, wading slowly in deep warm water builds up the muscles in the leg, with minimal danger to the healing joint. Our sister business, which is on site, conducts the hydrotherapy, ideally twice a week for 6 weeks (12 sessions).

Sometimes, prior to, or simultaneous with the hydrotherapy sessions we give a course of four, once a week, injections of a drug designed to curb the inflammation in the healing joint.

Some of our stifle patients have continued to attend regularly for hydrotherapy, as the dogs have enjoyed themselves so much and to keep them in peak physical condition.


What about the arthritis?
Unfortunately, having had a luxating patella and a surgical correction there is an inflammatory process leading to the establishment of arthritis. Arthritis is a progressive disorder but there are many things that can and should be done to slow down the progression of the arthritis and minimise its impact of your pet’s quality of life. The surgery is a significant part but there are four cornerstones to managing the stifle arthritis or indeed any arthritis.


They are:

  1. Weight control. Being too heavy does not cause arthritis but if your dog is too heavy and has arthritis or an injury it progresses much more quickly, the disability is then magnified leading to the possibility of failure in another leg.
  2. Regular and reasonable exercise. Too much or strenuous activity is just as bad as not enough. If your dog has arthritis you need to look at your pet’s routine, curb the excesses and make time for some gentle exercise every day. Do not fall into the “weekend warrior” where your dog bags some Munroes at the weekend and is wiped out for most of the week, recovering just in time to give his joints another battering the next weekend.
  3.  Supplements, in the form of additions to normal diet or the shift to a “joint” diet is a major part of looking after the joints, next week, next month and next year.
  4.  Drugs, surprising, are the last item, not the first. There is undoubtedly a role for drugs to manage the stiffness and inflammation especially early on after surgery or when there is a flare up. However, there may be long periods when daily administration of drugs is not necessary.

At Oak Tree Vet Centre, we are well placed to guide you though making the most appropriate choices for your pet.

Why come to Oak Tree Vet Centre?
Alistair Marks, the founder of Oak Tree Vet Centre, is retiring at the end of June 2018. We hope to offer Ridgestop again soon

Our surgeons are ably assisted by a team of six Registered Veterinary Nurses who are very active in the provision of care, at all stages. We are careful to provide the best experience during the perioperative period for your pet and enthusiastic assistance during rehabilitation, which most dogs thoroughly enjoy.

We are content to make a direct claim to most of the significant insurance companies if we have sight of the original policy documents prior to the commencement of treatment. Please read our practice brochure and speak to us to learn more about this aspect of our service.

Referral to Oak Tree Vet Centre
Whilst many of our luxating patella cases are drawn from our own clients’ pets, we are accepting more and more referral cases, as few surgeries have set themselves up for these procedures and have not undertaken the necessary training for the Ridgestop.

Whilst we can give you general information about the procedure in the typical patient, your own vet must be the one that decides with you, a referral is the preferred treatment route for your pet. He or she will have decided that your dog is sufficiently healthy to undergo this procedure, from clinical examination and usually by the taking of a general blood test profile.

The cost of the procedure in 2017 is between £1200 and £1400 including VAT and covers all the aspects of the surgical procedure on the day, including post operative x-rays. The exact cost depends upon size and the actual surgery recommended. In addition to the surgery charge, you might need to purchase antibiotics and pain medication. We are very happy to liaise with your vet so you can be supplied some or all of your anticipated medicines, by your usual practice, in anticipation of the surgery.

We’ll give you written instruction as to what to do post op. It is important that the stitches are not chewed and your vet or we can sell you a plastic cone, if required.

We like to check the wound at three days and again at ten days when the stitches are removed. A final check is made at 4 weeks post op and all of these checks are included in the fee.

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