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By Dr Daisy May, MRCVS BVSc, VetPrac
Naming the problem is not the same as understanding it: a vaguely philosophical notion that is especially true with medial patellar luxation.
The moment we assign a grade, the case can feel satisfyingly contained. Grade II. Grade III. Medial. Painful. Documented. Bite avoided (muzzle was worth it despite owner eye roll). Plan discussed briefly with client. Done.
The dog feels filed away in the correct mental drawer. Yet we need to be sure that we aren’t relying on grading as a form of closure.
The grade tells you where the patella is and where it roams. And indeed, whether it has become stuck on the wrong side of the trochlear groove like a Roomba snagging on the edge where your kitchen floor meets the hallway (ridiculous robot).
It does not tell us how much the dog hurts, whether the limb is conformationally straightforward, whether the stifle is stable, or even whether MPL is acting as the decoy for a concurrent CCL problem.
Smallies GPs see MPL often enough to recognise it almost by reflex; the MPLs spotted out of the car window alone probably number in the tens or hundreds every year. Being a vet ruins everything – that cute Pom passing by is now a bit of a downer.
In any case – the danger with a familiar diagnosis is sometimes not that we miss it. It’s that we trust it too quickly.
Let’s not allow it to slip our collective hive-mind that MPL can be an incidental finding, a distraction, contributory factor, or part of a bigger alignment issue (apologies for making us sound like clinical bees). And sometimes, particularly in the older small-breed dog who’s always had a skip, it becomes the convenient explanation that distracts us from the stifle’s newer, messier truth.
Really, that’s where MPL gets interesting: not at the point of diagnosis, but at the point where we decide what the diagnosis means. And heed these words, for the mercy of kneecaps everywhere: MPL punishes oversimplification. Or rather more crucially: oversimplification punishes the poor dog.
So, is grading pointless? Should we chuck it out the window in favour of applying ourselves to a thoroughly time-consuming process of trying to describe the tracking of each patella to a tee, and to find the exact right words in a pinch for every part of the equation?
Well…no actually. Probably not. At least, not at that first visit, stress-tested by time, with a likely excited or anxious dog who won’t stand still for long and an owner who may need easing into the idea of a chronic, potentially surgical issue.
Grading matters because it gives us a shared – and efficient – language (cue second hive-mind reference). This, in a way, is the whole point of clinical notes, especially when it might not be you who sees the dog next. Also very useful when you see a hundred different cases in between visit one and visit two.
It’s a starting point that guides treatment conversations and makes our clinical notes more useful than ‘lame’. But it’s obviously not the whole story, as we’ve clearly and somewhat evangelically now established. It’s only the opening line.
A Grade II medial patellar luxation in one dog may be an incidental finding discovered during a vaccination exam. In another, it may explain a very real pattern of pain, skipping, reduced activity or progressive lameness.
In this second scenario, that little pebble-like sesamoid could be creating significant daily discomfort, nagging away at that dog’s mental health. Yup – dogs absolutely do have mental health; it’s 2026.
Same label. Different patient. Different plan.
‘Luxating patella’ makes the patella the main character. It certainly is taking up a lot of space in the plot, but most developmental or non-traumatic MPL cases are better understood as a problem of extensor-mechanism and limb alignment, not simply that the body’s biggest sesamoid is rebelling.
The quadriceps mechanism, femoral trochlea, tibial tuberosity, soft tissue balance and sometimes broader limb conformation all have their say. In higher-grade cases, skeletal deformities such as distal femoral varus or tibial torsion can become part of surgical decision-making.
During the examination and note-making process, we shouldn’t only be asking ourselves ‘What grade is this?’, but also:
How often is this dog skipping? Or indeed, is it consistently and/or currently lame?
Is the lameness proportional to the luxation?
Is there pain, effusion, crepitus, reduced range of motion or muscle atrophy?
What about medial buttress?
Where indicated by signalment or clinical suspicion: should I carry out a cranial drawer and tibial compression test (and will I need some sedation for that?)
Has the owner noticed a change in frequency, duration or severity of lameness? If worse, was that sudden or a slow-build?
What’s the limb conformation like?
Is there another disease process hiding behind or acting in tandem with the MPL?
The older small-breed dog with the known and largely ignored (for whatever reason) MPL is particularly skilled at catching us out. One week the lameness changes; now Frankie is slower to rise, reluctant on stairs, and less keen to jump up onto his owner’s lap.
The temptation is to blame the familiar abnormality, but sometimes we’re accusing the wrong suspect, and in doing so leaving a criminal on the loose. Emphasis on loose – or possibly on snapped.
Bodies love a good combo:a dog with MPL can also have CCL pathology, and the two conditions can muddy the waters beautifully.
It shouldn’t be automatically assumed that the patella thing sort of just got worse. Consider CCL disease, meniscal injury, worsening OA, or another stifle problem. Even referred pain from the hip (this last one can be important: OA commonly strikes in more than one place).
Familiar or known diagnoses have a special sort of gravity: they pull clinical signs towards themselves.
Slow down (as much as realistically feasible – or book a longer follow-up) and ask yourself those questions. The real skill is not just identifying MPL, but rather, working out what that diagnosis and grade mean for this dog.
Hands-on and targeted training in MPL assessment and correction is key for those GPs wishing to take these cases further and get a little more detail in terms of assessment and planning. Plus – for the eager – getting started personally with surgical management.
For those looking at building broader orthopaedic foundations, a practical grounding in small animal orthopaedics can help make the stifle feel less like an isolated puzzle and more like part of a bigger system.
The grade still matters and we should keep using it, but maybe we should treat it less like the answer and more like a prompt. And maybe we should be looking less at the kneecap, and more at the leg.
Margie is the Director of VetPrac and a globally respected veterinary anaesthetist, dedicated to practical, inclusive, and human-centred veterinary education. She began her career in general practice across Australia and the UK, grounding her teaching in real-world clinical experience. Specialising in anaesthesia and analgesia, Margie earned Membership of the Australian and New Zealand College of Veterinary Scientists, completed a residency at Cornell University (USA), and became a Diplomate of the American College of Veterinary Anesthesia and Analgesia. Her academic roles in the USA and Australia have focused on veterinary education, communication, and skills training. Since 2019, Margie has led VetPrac, delivering hands-on workshops and online courses that continue to inspire lifelong learning for veterinarians, nurses, and technicians.
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