Health
What do the patellar luxation grades mean?
They describe joint stability on examination, from grade I where the kneecap only moves under pressure to grade IV where it is permanently dislocated.
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Patellar Luxation in Shetland Sheepdogs: Grades, Anatomy and Surgery
Quick answer
What do the patellar luxation grades mean?
They describe joint stability on examination, from grade I where the kneecap only moves under pressure to grade IV where it is permanently dislocated.
The grade written on your dog's notes describes a specific finding on examination, and it is the number that decides whether an operation is on the table.
Owners weighing up a surgeon's recommendation, and anyone who has been given a grade without an explanation of what it means or what would change it.
Important reminder
This guide is not medical advice. If your dog shows pain, sudden behavior change, or worsening symptoms, consult a licensed veterinarian.
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What this problem looks like
Patellar luxation is a documented Shetland Sheepdog condition in which misalignment of the extensor mechanism allows the kneecap to leave its groove. It is graded I to IV on examination, and that grade, combined with how the dog is actually coping, determines whether surgery is appropriate. Most affected Shelties sit at the lower grades and are managed conservatively for life; the ones that progress face a well-established but demanding surgical pathway.
Common triggers
- Inherited conformation, including a shallow trochlear groove and a misplaced tibial attachment point
- Progressive wear of the groove from repeated luxation, which worsens the grade over years
- Stretching of the joint capsule on one side and contraction on the other
- Excess weight increasing the force through a poorly aligned joint
- Repetitive sharp turning and hard landings on slippery surfaces
Common in the breed and one of its five documented health conditions. Among small dogs generally it is one of the most frequently diagnosed orthopaedic problems. The majority of affected Shelties are grade I or II and never need an operation, which is worth holding onto when a diagnosis first arrives.
Why this happens
Breed factors
The underlying fault is skeletal alignment rather than the kneecap itself. In affected Shelties the groove at the end of the femur may be shallow, the bony attachment of the patellar ligament on the tibia may sit too far medially, and in severe cases the femur itself may be subtly bowed. Those features are inherited and are why patellar luxation sits on the Shetland Sheepdog's documented health list and why responsible breeders have stifles graded. MDR1 drug sensitivity, also documented in this breed, governs the anaesthetic planning that any surgical correction requires.
Environment factors
Environment does not create the deformity but it determines how quickly the joint deteriorates. Hard slippery floors produce lateral forces on take-off that lever the kneecap out repeatedly. Jumping down from furniture and cars adds high-impact loading. Body weight multiplies every force through the joint and is concealed by the breed's double coat. And a dog that has lost hind end muscle, whether from inactivity or from another sore joint, has lost the active stabiliser that keeps the patella tracking correctly.
What you can do at home (once it is not an emergency)
When to talk to your vet
Same day: a hind leg held up continuously rather than for a stride or two, a kneecap that has luxated and will not go back, refusal to bear weight, or a sudden dramatic worsening, which in a dog with an unstable stifle may mean a torn cruciate ligament rather than the patella. Also same day for any swelling, heat or severe pain around the knee after surgery. Within a few weeks: a rising frequency of skipping, new stiffness after rest, reluctance to jump onto things the dog previously managed, or thigh muscle that feels smaller on one side. Ask for a grade for each stifle and a referral opinion if the grade has changed.
At home, alongside your vet's plan
- Ask for both stifles to be graded at each annual examination and keep the numbers, since a rising grade is the clearest evidence that management is losing ground.
- Get a surgical opinion before arthritis is extensive rather than after, since the joint's condition at the time of surgery shapes the long-term result.
- Confirm and record the MDR1 genotype before any surgical consultation, because the anaesthetic plan depends on it and two procedures may be needed.
- Prepare the house for the confinement period in advance: a pen, non-slip flooring on the route to the garden, and a plan for toileting on a lead.
- Commit to formal physiotherapy as part of the surgical budget rather than treating it as an optional extra, because muscle rebuilt afterwards determines the outcome.
- Keep the dog at the lean end of its weight range throughout, checked by hand under the coat.
More Shetland Sheepdog health & behavior issues
- ARVC in Shetland Sheepdogs: Risk, Signs & Reality Check
- DCM and Sheltie Puppy Murmurs: Separating the Two Worries
- GDV Look-Alikes in Shetland Sheepdogs: What Else Swells the Belly
- IVDD in Shetland Sheepdogs: Why This Is Not a Dachshund Spine
- Pancreatitis & Diabetes in Shetland Sheepdogs
- Pancreatitis in Shetland Sheepdogs: The Thyroid Connection
- Sheltie IVDD Type I: The Acute Extrusion Emergency
- Shetland Sheepdog Heart Conditions: Sorting Signal From Noise
- BOAS and Shetland Sheepdogs: Why This Does Not Apply
- Cherry Eye in Shetland Sheepdogs: Rare, But Know the Rule
- Separation Anxiety in Shetland Sheepdogs: Why This Breed Struggles
- Shetland Sheepdog Allergic Reactions: Signs & Response
- Shetland Sheepdog Allergies: Itch, Ears & Skin Care
- Skin Allergies in Shetland Sheepdogs: Signs, Costs and What to Do
- Skin Infections in Shetland Sheepdogs: Hot Spots and Coat
Patellar Luxation in other breeds
- Cavalier King Charles Spaniel Patellar Luxation: Signs
- Cocker Spaniel Patellar Luxation: Signs, Costs & Prevention
- English Bulldog Patellar Luxation: Signs, Costs & Prevention
- English Cocker Spaniel Patellar Luxation: Signs & Costs
- German Shepherd Patellar Luxation: Signs, Costs & Prevention
- Havanese Patellar Luxation: Signs, Costs & Prevention
- Jack Russell Terrier Patellar Luxation: Signs & Costs
- Maltese Patellar Luxation: Signs, Costs & Prevention
- Miniature Schnauzer Patellar Luxation: Signs & Costs
- Poodle Patellar Luxation: Signs, Costs & Prevention
See all Shetland Sheepdog health problems, which breeds are prone to patellar luxation, or the full Shetland Sheepdog breed guide for temperament, exercise needs and ownership costs.
What to expect, and how you know it is working
The surgery itself is a single day. Strict confinement runs four to six weeks, followed by a graded return over six to eight weeks with physiotherapy throughout. Most dogs are walking on the leg within days and using it well by two months. Return to agility or comparable sport is usually a six month proposition. If both stifles need operating, allow several months between them.
Success is a dog that uses the leg normally, has rebuilt symmetrical thigh muscle, and is not skipping. It is not a knee that will look normal on radiographs, since the arthritis already present does not reverse. For conservatively managed dogs, success is a grade that has not changed in five years. For surgical dogs, it is a Sheltie that goes back to doing what it wants to do without the household organising itself around the knee.
The four grades, defined by what the vet can do with their thumb
Grading is done by manipulation during examination and it is a description of joint stability, not of how much the dog is limping. Both stifles are graded separately, and they are often different.
- Grade I: the kneecap sits in its groove normally and can be pushed out by the examiner, but returns immediately on its own. Usually no clinical signs at all. Monitored, not treated.
- Grade II: the kneecap sits in place but luxates during normal movement, then returns spontaneously or when the leg is extended. This is the classic skipping dog. Surgery is discussed on the basis of symptoms and progression rather than the grade alone.
- Grade III: the kneecap is out of the groove most of the time and can be replaced by the examiner, but comes straight back out. Gait is persistently abnormal. Surgery is usually recommended.
- Grade IV: the kneecap is permanently out and cannot be replaced manually. The limb is often turned inward and the dog may crouch or refuse to extend the leg. Surgery is the only meaningful option and is more complex.
- Direction matters too. In small breeds the kneecap usually luxates medially, toward the inside of the leg. Lateral luxation is less common and can indicate a different underlying deformity.
- Grades can worsen over time as the groove wears shallower and the soft tissues stretch, which is why a grade recorded five years ago is not a current description.
What a surgeon is actually correcting
There is no single patellar luxation operation. A surgeon assesses which of several anatomical faults are present and combines procedures accordingly, which is why costs and recovery times vary so widely between dogs.
Deepening the groove addresses a trochlea that is too shallow to hold the kneecap. A wedge or block of cartilage and underlying bone is lifted, the bed beneath is deepened, and the piece is replaced, preserving the joint surface.
Moving the attachment point addresses the commonest underlying fault. The bony bump on the shin where the patellar ligament attaches sits too far to the inside, so the whole mechanism pulls the kneecap off-centre. The surgeon cuts that bump free, moves it outward, and pins it in its new position.
Soft tissue balancing tightens the stretched capsule on one side of the joint and releases the tight tissue on the other.
In severe grade IV cases with genuine bone deformity, corrective osteotomy of the femur may be needed, which is a considerably bigger undertaking.
For a Shetland Sheepdog all of this happens under general anaesthesia, sometimes more than once if both stifles are done separately, which makes MDR1 genotype a non-negotiable piece of information rather than a detail. Have it tested and recorded before the surgical consultation, not after.
What to do next about patellar luxation in Shetlands
If you think your Shetland has patellar luxation, the plan is three steps: write down what you have seen and when it started, book a veterinary appointment rather than waiting for the next flare, and take video of the behaviour or symptom before you go — the thing you are worried about rarely happens in the consulting room. Screening in the parents covers collie eye anomaly, mdr1 drug sensitivity, dermatomyositis.
What the vet visit should produce is a diagnosis and a written plan, not just reassurance: what is being ruled out, what the monitoring interval is, and which signs mean you come back sooner. Ask what the treatment costs across a year rather than per visit, because that is the number that decides whether you are managing this condition or reacting to it.
Between appointments, keep a short log — dates, what you saw, what changed. It is the single most useful thing an owner brings to a follow-up, and for patellar luxation it is often what separates a clear pattern from a guess.
Grade II at four, grade III at six, and the decision in between
Aled's Sheltie, Cerys, was recorded as grade II on the left stifle at four. She skipped occasionally and it did not seem to bother her, so nothing was done, which was reasonable advice at the time. At six the same vet graded her III. She was skipping most days, had lost noticeable muscle from the left thigh, and had started refusing the stile on their usual walk. There was already early arthritic change on the radiographs. Her surgeon deepened the groove and moved the tibial attachment point outward. The anaesthetic was planned around a carrier MDR1 result that Aled's practice had recorded when she was a puppy. She was confined for five weeks, which Aled describes as the hardest five weeks of dog ownership he has had, and got through it on scentwork games and a food-dispensing puzzle. At eight she is sound, symmetrical and back over the stile. Her surgeon's one comment was that the operation would have gone better at four than at six, because the arthritis would not have been there.
Key takeaway: The grade is a moving number, and the joint's condition when you operate determines the ceiling on the result. Have both stifles graded annually, and treat a rising grade as the prompt for a surgical opinion rather than waiting for the dog to stop coping.
Frequently asked questions
Does a grade II kneecap need surgery?
Not automatically. Grade II covers a wide range, from a dog that skips twice a month to one that skips constantly and is developing arthritis. The decision rests on how often it luxates, whether that frequency is increasing, whether the dog is showing pain or muscle loss, and what the other stifle is doing.
Both my Sheltie's knees are affected. Are they done together?
Usually not. Staging the surgeries lets the dog use one sound leg while the other recovers, which is safer and produces better rehabilitation. It does mean two anaesthetics, which is a specific consideration in an MDR1 breed and worth discussing with the anaesthetist rather than assuming.
What is the success rate?
Good in experienced hands for grades II and III, with most dogs returning to normal or near-normal function. Complication rates rise with grade, with severity of bone deformity, and where an owner cannot enforce the post-operative restriction. Ask your surgeon for their own outcomes rather than general figures.
Will surgery prevent arthritis?
It slows the process rather than preventing it. Arthritis that has already developed does not reverse, and the joint has been abnormal since birth. What surgery buys is the removal of ongoing abnormal wear, which is why operating before extensive arthritis has developed produces better long-term results.
What does the recovery actually involve?
Strict confinement for several weeks with lead-only toileting, then a graded return over a further six to eight weeks, usually with formal physiotherapy. Full return to sport takes longer. The restriction phase is the part that determines the outcome and the part that most owners underestimate.
Is this inherited? Should affected dogs be bred?
Patellar luxation has a hereditary component and is documented in this breed, which is why Sheltie breeders have stifles examined and graded and why the results should be part of any breeding decision. If you are buying a puppy, ask about it alongside the eye certification and MDR1 status.
Can an unstable kneecap cause other injuries?
Yes. A stifle that is chronically maltracking loads the cruciate ligament abnormally, and dogs with long-standing patellar luxation have a higher rate of cruciate injury. A sudden severe lameness in a dog with a known luxating patella should be examined rather than assumed to be the kneecap again.
Quick answers
View more answersHealth
At what grade is surgery usually recommended?
Grade III and IV almost always, grade II depending on symptoms and progression, grade I rarely. The dog's clinical picture matters as much as the number.
Costs
How much does patellar surgery cost?
Commonly two to four thousand dollars per stifle including imaging and follow-up, and a Sheltie may need both knees done at different times.
Living
How long is the recovery?
Several weeks of strict confinement followed by six to eight weeks of graded return, with formal physiotherapy through most of that period.
Health
Why does the anaesthetist need the MDR1 result?
Because the genotype determines which sedative and anaesthetic agents are appropriate in a Shetland Sheepdog, and this surgery may mean two separate anaesthetics.
Related DogBreedCompass guides
- living with a Sheltie's luxating patellas – The day-to-day management side and the household changes that reduce luxation frequency.
- cruciate ligament injuries in Shelties – An unstable stifle raises the risk of cruciate ligament rupture.
- drug sensitivity in Shetland Sheepdogs – Anaesthetic planning in this breed is dictated by MDR1 status.
- keeping a Sheltie lean – Weight is the load the repaired joint carries on every stride.
- Shetland Sheepdog breed guide – Full breed profile listing patellar luxation among documented conditions.
- Sheltie insurance claim patterns – Stifle surgery is typically the single largest claim in this breed.
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