Patellar Luxation in Dogs: Grades, Surgery, and Recovery Guide
This article is reviewed for clinical accuracy. Always consult your veterinarian for diagnosis and treatment.
Key Takeaways
- Patellar luxation is a condition in which the patella (kneecap) slips out of the femoral trochlear groove, the channel at the base of the femur in which it normally rides; the patella is a sesamoid bone embedded within the quadriceps tendon and acts as a pulley to amplify the force of the quadriceps muscle group as it extends the stifle (knee) joint; its correct tracking within the trochlear groove depends on the alignment of the entire quadriceps mechanism, from the hip through the femur, trochlear groove, patella, patellar ligament, and tibial tuberosity (the bony prominence on the tibia to which the patellar ligament attaches); in patellar luxation, a developmental malalignment of this mechanism, usually involving a combination of a shallow or dysplastic trochlear groove, internal rotation or bowing of the distal femur, and medial displacement of the tibial tuberosity, causes the patella to track medially (in most dogs) or laterally (in large breeds) out of its groove.
- Patellar luxation is one of the most common orthopedic conditions in dogs overall and is the single most common orthopedic condition in small and toy breeds; it is classified as medial patellar luxation (MPL), in which the patella luxates toward the midline of the body, or lateral patellar luxation (LPL), in which it displaces away from the midline; MPL accounts for approximately 75 to 80 percent of all canine patellar luxation cases and is strongly associated with small and toy breeds; LPL is more common in large breeds; bilateral patellar luxation (affecting both stifles) occurs in approximately 50 percent of dogs diagnosed with patellar luxation, though one side is often more severely affected than the other; the condition has a strong hereditary component, and breeding dogs with Grade II or higher patellar luxation is discouraged.
- Patellar luxation severity is graded on a four-grade scale: Grade I (the patella can be manually pushed out of the groove during palpation but immediately returns to the correct position when pressure is released; the dog is usually asymptomatic or shows only very occasional lameness); Grade II (the patella spontaneously luxates during normal activity, often during flexion of the stifle, but can be manually reduced; classic clinical sign is intermittent “skipping” gait in which the dog suddenly holds up the affected rear leg for a few steps, then shakes or extends the leg and resumes normal walking as the patella self-reduces; Grade II is the most commonly diagnosed grade in clinical practice); Grade III (the patella is permanently luxated in most positions but can be manually reduced with moderate effort; persistent lameness but the dog may bear some weight); Grade IV (the patella is permanently luxated and cannot be manually reduced; the trochlear groove is severely shallow or absent; the tibia may be internally rotated up to 90 degrees; the dog bears little or no weight on the limb and the limb is held in a characteristic flexed and rotated posture).
- The intermittent “skipping” gait of Grade II patellar luxation is the most recognizable and frequently owner-reported sign: the dog is walking or running normally, then suddenly skips on one rear leg for 2 to 4 steps, sometimes shaking or stretching the leg out behind it, then resumes normal gait; the skipping occurs when the patella luxates medially during stifle flexion (most often during the swing phase of the gait cycle) and resolves when the dog extends the stifle and the patella snaps back into the groove; many owners interpret this as the dog stepping on something sharp or having a momentary cramp, not realizing it is a structural orthopedic issue; the frequency of skipping episodes typically increases over time as the trochlear groove becomes progressively shallower from wear and as the skeletal malalignment progresses.
- Patellar luxation and cranial cruciate ligament (CCL) rupture are closely related: Grade II and higher medial patellar luxation significantly increases the risk of CCL rupture in the same stifle because the skeletal malalignment that causes the patella to track incorrectly also creates abnormal shear forces on the CCL during weight bearing; dogs with MPL have been shown to be 3 to 4 times more likely to develop concurrent or subsequent CCL disease than dogs without MPL; when a dog presents with both patellar luxation and CCL rupture in the same stifle, both conditions must be surgically corrected at the same time; failing to correct the patellar luxation while repairing the CCL leads to higher failure rates for the CCL repair due to ongoing abnormal biomechanical forces.
- Surgical treatment is recommended for Grade II dogs with frequent lameness, for all Grade III to IV dogs, and for Grade II dogs with concurrent CCL disease; the three main surgical techniques are trochlear modification (deepening the trochlear groove by trochlear wedge recession or trochlear block recession so the patella cannot easily luxate), tibial tuberosity transposition (moving the tibial crest laterally to realign the pull of the patellar ligament), and corrective osteotomy (cutting and realigning the femur or tibia when severe bone deformity is present); most surgeries combine trochlear modification with tibial tuberosity transposition; the prognosis after surgical correction is good to excellent in more than 90 percent of Grade II to III dogs, with most returning to full function within 4 to 8 weeks; Grade IV cases and those requiring corrective osteotomy have a more guarded prognosis and longer recovery.
The 3-year-old Yorkshire Terrier had been doing it since she was about 18 months old: every few minutes during a walk, she would suddenly hold her right rear leg up for a few steps, give it a little shake, then carry on as if nothing had happened. Her owner assumed it was a quirk. By her third birthday the skipping was happening every few steps and she had started avoiding stairs. At her annual wellness exam, the veterinarian flexed and extended the stifle, applied light pressure, and felt the patella pop medially out of the groove with a soft click, then self-reduce when the leg was extended. The diagnosis was Grade II medial patellar luxation, right stifle, with Grade I involvement of the left. The veterinarian explained that Grade II on the right was starting to cause wear on the trochlear cartilage and that a radiograph showed mild trochlear groove flattening, consistent with ongoing articular cartilage erosion from years of abnormal patellar tracking. Surgery was recommended before the joint changes progressed further.
Stifle and Patellar Anatomy
The stifle (canine equivalent of the human knee) is a complex joint involving three bones: the distal femur, the proximal tibia, and the patella. Understanding patellar luxation requires understanding the normal mechanics of the quadriceps extensor mechanism:
- Femoral trochlear groove: a groove on the cranial surface of the distal femur between two elevated ridges called the trochlear ridges; the patella sits in this groove and rides within it as the stifle flexes and extends; in normal dogs the groove is sufficiently deep to retain the patella through the full range of stifle motion; in patellar luxation, the groove is abnormally shallow (trochlear dysplasia), reducing the mechanical barrier to patellar displacement
- Patella: a sesamoid bone embedded within the quadriceps tendon; its caudal articular surface is coated with hyaline cartilage that contacts the trochlear articular cartilage; the patella acts as a pulley that increases the mechanical advantage of the quadriceps muscle group by increasing the moment arm of the extensor force at the stifle
- Quadriceps mechanism alignment: the line of action of the quadriceps force (from the quadriceps muscle group through the patella to the tibial tuberosity via the patellar ligament) must be straight or very close to straight for the patella to track centrally in the groove; any angular deviation between the femoral shaft, the trochlear groove axis, and the tibial tuberosity creates a bow-string effect that pulls the patella medially or laterally out of the groove; in medial patellar luxation, the tibial tuberosity is displaced medially relative to the trochlear groove, and the distal femur is often internally rotated or bowed, directing the quadriceps pull toward the midline
- Tibial tuberosity: the bony eminence on the cranial tibial plateau to which the patellar ligament attaches; its position relative to the trochlear groove determines the direction of the patellar ligament’s pull; a medially displaced tibial tuberosity pulls the patella medially; tibial tuberosity transposition surgery moves this attachment laterally to restore normal alignment
Grading Scale and Clinical Signs
| Grade | Behavior of Patella | Typical Clinical Signs | Trochlear Groove |
|---|---|---|---|
| Grade I | Patella remains in groove during normal activity; can be manually luxated with firm pressure but immediately returns to the groove when pressure is released | Usually asymptomatic; occasional very brief lameness that resolves immediately; often discovered incidentally during routine palpation; may never progress | Shallow but functional; trochlear ridges present but reduced in height |
| Grade II | Patella spontaneously luxates during stifle flexion (typically the swing phase of gait); self-reduces when the dog extends the stifle; can also be manually luxated and manually reduced | Intermittent “skipping” gait: dog holds up one rear leg for 1 to 4 steps, sometimes shakes or stretches the leg, then resumes normal gait as the patella self-reduces; may occur several times per walk or only occasionally; frequency increases over time; dog may be comfortable at rest; most common grade presenting for veterinary evaluation | Shallow to moderately dysplastic; progressive articular cartilage erosion from abnormal patellar contact over time |
| Grade III | Patella permanently luxated in most positions; can be manually reduced with moderate effort but immediately re-luxates when pressure is released | Persistent lameness; dog bears weight on the limb but with a characteristic crouched or bow-legged stance; reluctance to exercise; may show muscle atrophy of the affected limb; no more skipping episodes (patella stays out rather than intermittently luxating and reducing) | Significantly shallow or absent trochlear groove; substantial articular cartilage damage from chronic abnormal contact |
| Grade IV | Patella permanently luxated; cannot be manually reduced or requires excessive force; tibia may be internally rotated 60 to 90 degrees relative to the femur | Non-weight-bearing or toe-touching lameness on the affected limb; the limb is often held in a fixed flexed, internally rotated position; severe muscle atrophy; bilateral Grade IV cases produce a characteristic crouching, bow-legged gait with the dog walking on its hocks; severe functional impairment | Trochlear groove absent or convex; severe skeletal deformity of the distal femur and proximal tibia; cartilage and subchondral bone destruction |
Medial vs. Lateral Patellar Luxation
Medial Patellar Luxation (MPL)
Medial patellar luxation is by far the most common form in dogs, accounting for approximately 75 to 80 percent of cases. It occurs almost universally in small and toy breeds and is the result of a developmental varus (inward-bowing) deformity of the distal femur combined with medial displacement of the tibial tuberosity. The characteristic pathoanatomy includes: coxa vara (reduced neck-shaft angle of the femur), internal torsion of the distal femoral metaphysis, shallow femoral trochlear groove, medially displaced tibial tuberosity, and medial displacement of the quadriceps mechanism. Because the pull of the quadriceps is directed medially, the patella is pulled out of the groove medially during stifle flexion. The most at-risk small breeds are Yorkshire Terrier, Chihuahua, Pomeranian, Toy and Miniature Poodle, Maltese, Bichon Frise, Boston Terrier, Miniature Pinscher, and Pekingese.
Lateral Patellar Luxation (LPL)
Lateral patellar luxation is less common overall but is more frequently seen in large and giant breeds, in which the pathoanatomy is a valgus (outward-bowing) deformity of the distal femur combined with lateral displacement of the tibial tuberosity. The breeds most commonly affected include Labrador Retriever, Flat-coated Retriever, Boxer, and some large mixed-breed dogs. Lateral patellar luxation in large breeds tends to present with more severe skeletal deformity and a higher rate of concurrent CCL disease than MPL in small breeds. LPL also occurs in small breeds but is much less common than MPL.
Relationship Between Patellar Luxation and CCL Rupture
The connection between medial patellar luxation and cranial cruciate ligament (CCL) rupture is one of the most clinically important aspects of this condition and must be understood before treatment decisions are made. The skeletal malalignment that causes the patella to track medially also creates two types of abnormal force on the CCL:
- Increased tibial plateau angle: the internal femoral torsion associated with MPL increases the effective tibial plateau angle (the slope of the tibial plateau relative to the long axis of the tibia), which increases cranial tibial thrust (the shear force that drives the tibia forward relative to the femur during weight bearing); this increased shear force is a primary mechanism of CCL rupture in dogs, and it is amplified in dogs with MPL
- Abnormal biomechanical loading of the CCL: when the patella is luxated medially, the patellar ligament pulls medially on the tibial tuberosity, rotating the tibia internally; this rotational force places abnormal tension on the CCL, contributing to fiber fatigue and eventual rupture
In practice, a dog presenting with a Grade II or III MPL and sudden acute severe lameness should be palpated carefully for concurrent CCL rupture (positive cranial drawer sign or tibial thrust test) in addition to the patellar instability. Finding both in the same stifle is common, and the surgical plan must address both simultaneously.
Diagnosis
Physical Examination and Palpation
Patellar luxation is diagnosed by physical examination through palpation of the stifle. With the dog in lateral recumbency or standing, the examiner flexes and extends the stifle while applying medial pressure on the patella (for MPL testing) and lateral pressure (for LPL testing). The grade is assigned based on the patella’s behavior: whether it luxates only with applied pressure (Grade I), luxates spontaneously but reduces manually (Grade II), stays luxated but can be manually reduced (Grade III), or cannot be manually reduced (Grade IV). Both stifles are examined and graded, as bilateral involvement is common. Concomitant CCL stability is assessed with the cranial drawer test and tibial compression test.
Radiography
Radiographs of the stifle and full hindlimb are obtained to assess: the depth of the trochlear groove (best evaluated on a skyline or flexed stifle view), the degree of tibial tuberosity displacement, the presence and severity of angular and rotational deformities of the femur or tibia, the presence of concurrent osteoarthritis (joint space narrowing, periarticular osteophyte formation), and the tibial plateau angle (relevant when concurrent CCL disease is suspected). Radiographs are essential for surgical planning, particularly when corrective osteotomy may be needed for severe skeletal deformity.
Treatment Options
Medical Management
Medical management is appropriate for Grade I disease and selected Grade II cases with infrequent lameness and no progression. The goals are pain control, joint health support, and slowing articular cartilage degeneration:
- Weight management: the most impactful non-surgical intervention; excess body weight increases the load across an already mechanically compromised joint; achieving and maintaining ideal body condition score (BCS 4 to 5 out of 9) reduces pain and slows joint degeneration
- Controlled, low-impact exercise: leash walks on flat surfaces, swimming, and underwater treadmill therapy; avoid activities that involve repetitive jumping, quick direction changes, or stairs that provoke frequent luxation episodes
- NSAIDs: meloxicam (0.1 mg/kg once daily), carprofen (2.2 mg/kg twice daily), or grapiprant (Galliprant, 2 mg/kg once daily) for pain management during flare-ups; should not be used long-term without monitoring of renal and hepatic function
- Joint supplements: omega-3 fatty acids (EPA and DHA from fish oil), glucosamine-chondroitin sulfate combinations, and avocado-soybean unsaponifiables (ASU) have variable evidence for benefit in canine joint disease but are low-risk and may provide modest anti-inflammatory and chondroprotective effects
- Injectable polysulfated glycosaminoglycans (Adequan, administered intramuscularly every 3 to 4 days for 8 injections then monthly): inhibit destructive enzymes within joint fluid and may slow articular cartilage degradation; particularly popular in small breeds with early-grade patellar luxation
Medical management does not correct the underlying skeletal malalignment and does not prevent progression of articular cartilage damage from continued abnormal patellar tracking. Grade II dogs managed medically should be reassessed every 6 to 12 months; progression to more frequent lameness, increased grade on palpation, or development of radiographic joint changes is an indication to reconsider surgery.
Surgical Correction
Surgery is recommended for: Grade II dogs with frequent lameness (more than 2 to 3 skipping episodes per week), Grade II dogs with radiographic evidence of articular cartilage wear or osteoarthritis, all Grade III and Grade IV dogs, and any dog with concurrent patellar luxation and CCL rupture. The timing of surgery matters: earlier correction preserves more articular cartilage and prevents the development of secondary osteoarthritis, which is irreversible.
| Surgical Technique | Purpose | Indication |
|---|---|---|
| Trochlear wedge recession (TWR) | A V-shaped wedge of bone and cartilage is removed from the trochlear groove, the groove is deepened, and the wedge is replaced; the cartilage surface is preserved intact; this technique is generally preferred in young growing dogs and in dogs with remaining articular cartilage | Shallow or dysplastic trochlear groove; Grade II to III; standard component of most patellar luxation surgeries |
| Trochlear block recession (TBR) | A rectangular block of bone and cartilage is removed from the trochlear groove, the groove floor is deepened by removing a thin layer of subchondral bone, and the block is replaced; provides a deeper and wider trochlear groove than TWR | Severely shallow or absent trochlear groove; Grade III to IV; dogs with extensive trochlear dysplasia where TWR would not achieve adequate depth |
| Tibial tuberosity transposition (TTT) | The tibial tuberosity is osteotomized (cut free from the proximal tibia), moved laterally (for MPL) or medially (for LPL) to realign the pull of the patellar ligament with the center of the trochlear groove, and fixed in its new position with a pin and tension band wire or a bone screw | Medially or laterally displaced tibial tuberosity; almost always combined with trochlear modification; essential component of most patellar luxation surgeries |
| Femoral corrective osteotomy (distal femoral osteotomy, DFO) | The distal femur is cut and realigned (rotated and/or angulated) to correct severe femoral torsion or varus/valgus deformity, then stabilized with a bone plate; directly addresses the root cause of the patellar malalignment at the femoral level | Severe femoral torsion or varus deformity (typically Grade III to IV); cases where TTT alone cannot adequately correct alignment due to the severity of the underlying skeletal deformity |
| Tibial corrective osteotomy | The proximal tibia is cut and realigned to correct tibial torsion or angulation contributing to patellar luxation; may be combined with tibial plateau leveling osteotomy (TPLO) when concurrent CCL disease is present | Severe tibial deformity; concurrent CCL disease; Grade IV cases with significant tibial internal rotation |
| Soft tissue procedures (lateral retinacular imbrication, medial desmotomy) | Tightening the lateral joint capsule (for MPL) and/or releasing the tight medial joint capsule reduces soft tissue forces pulling the patella out of the groove; used as adjuncts to bony procedures, rarely adequate as sole treatment | Always combined with bony procedures in moderate to severe cases; may be used alone only for very mild Grade I to II cases with no significant trochlear dysplasia |
Recovery After Surgery
Recovery from standard patellar luxation surgery (combined trochlear recession and tibial tuberosity transposition) in a small dog typically proceeds as follows: strict rest and leash walks only for 6 to 8 weeks after surgery; gradual return to activity over weeks 8 to 12 with physical rehabilitation; full return to normal activity by 3 to 4 months. Complications include implant failure (pin migration, tension band wire loosening), re-luxation (occurs in approximately 10 to 20 percent of Grade III to IV cases and some Grade II cases), infection, and progression of osteoarthritis. Physical rehabilitation with a certified canine rehabilitation therapist (using range of motion exercises, underwater treadmill, and balance board exercises) significantly accelerates recovery and improves functional outcomes, particularly in dogs with muscle atrophy from prolonged pre-surgical lameness.
US Cost Overview for Patellar Luxation
| Service | Typical US Cost |
|---|---|
| Orthopedic examination | $80 to $200 (general practice); $300 to $600 (specialist) |
| Stifle radiographs | $150 to $350 |
| Full hindlimb radiographs (for deformity assessment) | $200 to $450 |
| Surgery: trochlear recession + tibial tuberosity transposition (small dog, one stifle) | $1,800 to $3,500 |
| Surgery with corrective osteotomy (one stifle) | $3,000 to $6,000 |
| Bilateral surgery (both stifles, same anesthetic or staged) | $3,500 to $7,000 |
| Combined patellar luxation + CCL surgery (one stifle, e.g. TPLO + TTT + trochleoplasty) | $4,500 to $8,000 |
| Post-operative radiographs and rechecks | $300 to $600 total over recovery period |
| Rehabilitation program (6 to 12 weeks) | $800 to $2,500 |
| Medical management (NSAIDs, supplements, annual monitoring, Grade I to II) | $300 to $700 per year |
Breed Predispositions
| Breed Category | Breeds | Type | Notes |
|---|---|---|---|
| Toy and small breeds (highest risk) | Yorkshire Terrier, Chihuahua, Pomeranian, Toy Poodle, Miniature Poodle, Maltese, Bichon Frise, Boston Terrier, Miniature Pinscher, Pekingese, Shih Tzu | Medial patellar luxation | Lifetime prevalence in some toy breeds estimated at 50 to 80%; bilateral involvement common; Grade II most frequent presentation; strong heritable component |
| Small-medium breeds | French Bulldog, Cocker Spaniel, Miniature Schnauzer, Lhasa Apso | Medial patellar luxation | French Bulldogs have a particularly high incidence; concurrent lumbosacral disease also common in this breed |
| Large breeds | Labrador Retriever, Flat-coated Retriever, Boxer, Great Pyrenees | Lateral patellar luxation (more common); medial also occurs | LPL in large breeds often associated with more severe skeletal deformity and higher rate of CCL disease; prognosis more guarded than MPL in small breeds |
| Mixed breed dogs | Any size | Either direction | Patellar luxation is common in mixed breeds, particularly those with toy or small breed heritage |
Age-Specific Considerations
Puppies (Under 12 Months)
- Patellar luxation in puppies is often detected at the first veterinary examination at 8 to 12 weeks of age in high-risk toy breeds; Grade I or mild Grade II detected at this age in a growing puppy does not necessarily predict the final grade at skeletal maturity, as the trochlear groove deepens and bone alignment consolidates during growth; some Grade I findings in puppies resolve by skeletal maturity (12 to 18 months in small breeds) without intervention; however, Grade II or higher that persists beyond 6 months in a growing small breed warrants monitoring every 3 to 6 months and early surgical consultation, as correcting skeletal deformity while the bone is still growing can achieve better long-term alignment than correcting after skeletal maturity
- Surgical timing in growing puppies requires careful consideration: surgery performed too early (before skeletal maturity) carries a risk of implant complications as bones grow, and some procedures (particularly those involving the trochlear groove or tibial tuberosity osteotomy) have historically been deferred until near skeletal maturity; however, contemporary orthopedic surgery opinion increasingly supports earlier surgical intervention in puppies with moderate to severe grades to prevent progressive articular cartilage damage; a board-certified veterinary surgeon should be consulted for Grade II or higher patellar luxation identified in a puppy under 12 months to determine the optimal timing
- All puppies of high-risk toy breeds (Yorkshire Terriers, Chihuahuas, Pomeranians, Toy Poodles) should have both stifles palpated at every wellness visit from 8 weeks through 18 months; early detection of progressive disease allows timely referral and intervention before secondary joint changes develop; owners of these breeds should be informed at the first puppy visit that patellar luxation is common in their breed so they recognize the skipping gait if it develops
Adult Dogs (1 to 8 Years)
- The majority of patellar luxation surgeries are performed in young to middle-aged adult dogs (1 to 5 years) who were either not diagnosed as puppies or whose disease progressed to warrant surgery in adulthood; adult dogs have mature skeletal architecture, making surgical planning more straightforward than in growing puppies; trochlear recession, tibial tuberosity transposition, and corrective osteotomy procedures are all well established in adult dogs and carry good to excellent prognoses in appropriately selected cases (Grade II to III with good articular cartilage remaining)
- Adult dogs with Grade II MPL who have been managed medically for 1 to 3 years and are now showing radiographic evidence of secondary osteoarthritis (periarticular osteophytes, subchondral bone sclerosis on the trochlear ridges) should have an honest conversation with their owner about the value of surgery at this stage; while surgery will not reverse existing osteoarthritis, it will halt the progressive articular cartilage damage caused by ongoing abnormal patellar tracking and may significantly reduce pain and improve long-term function compared with continued medical management alone
- Adult dogs that develop sudden severe lameness in a stifle with a known history of patellar luxation should be evaluated urgently for concurrent CCL rupture; the pre-existing patellar luxation increases the risk of CCL rupture significantly, and the owner and veterinarian should not assume the acute lameness is simply a worse patellar luxation episode; a positive cranial drawer test or tibial thrust test confirms CCL rupture and indicates combined surgical repair is needed; waiting several weeks “to see if it improves” in a dog with suspected concurrent CCL rupture and patellar luxation is not advisable, as joint damage accelerates with continued weight bearing on an unstable stifle
Senior Dogs (9 Years and Older)
- Senior dogs with long-standing patellar luxation often present with significant secondary osteoarthritis in the affected stifle, with radiographs showing osteophytes, joint effusion, and periarticular soft tissue thickening; in these dogs, the decision to pursue surgery versus medical management must weigh the degree of functional impairment against anesthetic risk and realistic post-surgical outcomes; a senior toy breed dog with Grade II MPL and mild osteoarthritis who is comfortable at rest and only occasionally skips may be a candidate for optimized medical management rather than surgery; a senior dog with Grade III MPL and persistent daily lameness who is otherwise healthy is still a reasonable surgical candidate with an expected good functional outcome
- Anesthetic risk in senior dogs should be evaluated with pre-anesthetic bloodwork (complete blood count, chemistry panel, urinalysis) and, for dogs with cardiac murmurs or respiratory signs, thoracic radiographs and echocardiography; small breed dogs (particularly Yorkshire Terriers) are prone to concurrent mitral valve disease as they age, and a cardiac evaluation is appropriate before any elective procedure under general anesthesia in a dog over 7 to 8 years with a detectable murmur; cardiac disease is a relative contraindication to elective surgery, not an absolute one, and must be assessed in context with the orthopedic need
- Senior dogs that are not surgical candidates due to age or systemic disease can have their quality of life significantly improved with optimized medical management: appropriate weight management, gabapentin (5 to 10 mg/kg every 8 to 12 hours) for neuropathic and arthritic pain, NSAIDs at the lowest effective dose with regular renal and hepatic monitoring, injectable Adequan, and physical rehabilitation (underwater treadmill, massage, passive range of motion); these dogs should be reexamined every 3 to 6 months to adjust the pain management protocol as their arthritis progresses
Myths and Facts About Patellar Luxation in Dogs
My dog’s knee pops out because it was injured jumping off the couch.
Patellar luxation in dogs is almost always a developmental condition caused by inherited skeletal malalignment, not trauma. The shallow trochlear groove, medially displaced tibial tuberosity, and femoral torsion that allow the patella to luxate are present from birth and become clinically apparent as the dog matures. A jump from furniture may trigger a luxation episode in a predisposed dog, but it did not cause the underlying condition. Trauma-induced patellar luxation (from a fracture or severe ligament injury) is rare and follows a very different clinical presentation than developmental patellar luxation.
Since my dog stops limping after a few steps and seems fine, I do not need to do anything about patellar luxation.
The brief self-resolution of the skipping episode does not mean the joint is undamaged. Every time the patella luxates and snaps back into position, the articular cartilage on the trochlear ridges and the patellar surface is damaged by abnormal contact stress. Over months to years, this repeated microtrauma erodes the cartilage progressively, leading to secondary osteoarthritis that causes persistent pain even when the patella is reduced. Grade II patellar luxation managed expectantly for 2 to 5 years frequently progresses to Grade III with irreversible joint changes; earlier surgical correction preserves more articular cartilage and achieves better long-term functional outcomes.
Patellar luxation surgery always requires cutting bones and has a long, painful recovery.
The complexity of patellar luxation surgery varies considerably by grade and the underlying skeletal anatomy. Grade II cases in small dogs with a shallow but functional trochlear groove and mild tibial tuberosity displacement are often corrected with a combined trochlear recession (which preserves the articular cartilage surface) and tibial tuberosity transposition; these dogs typically return to full activity within 6 to 10 weeks and experience minimal post-operative discomfort after the first week. Corrective osteotomy is reserved for severe skeletal deformity in Grade III to IV cases. An orthopedic surgeon can clarify what specific procedures are planned and what to realistically expect for recovery before you commit to surgery.
Red Flags: Signs That Require Prompt Veterinary Evaluation
- Sudden acute severe lameness (non-weight-bearing or toe-touching) in a dog with known patellar luxation: this pattern is different from the usual brief skipping and raises concern for concurrent CCL rupture, which requires orthopedic evaluation within 24 to 48 hours; do not assume it is just a “bad episode” of patellar luxation
- Skipping gait that has become much more frequent over the past 1 to 2 months (from occasional to multiple times per walk): this progression suggests the condition is worsening; increased luxation frequency is associated with progressive articular cartilage wear and widening trochlear groove dysplasia; a veterinary recheck and surgical consultation are warranted
- A dog that previously had a Grade II patellar luxation and successfully returned to normal activity after surgery, now showing recurrent lameness and skipping gait: this may indicate surgical re-luxation (patella has luxated again after surgery) or implant complications; requires radiographic evaluation and orthopedic reassessment
- Visible swelling, warmth, or significant pain on palpation of the stifle in a dog with patellar luxation: this level of joint reaction is not typical of Grade I to II patellar luxation alone and may indicate joint effusion, concurrent CCL injury, meniscal damage, or septic arthritis; prompt veterinary evaluation is needed
- A young puppy (under 6 months) of a high-risk toy breed that is reluctant to bear weight on one or both rear legs or that assumes an unusually crouched posture: Grade III to IV patellar luxation can be present from a very young age in severely affected individuals; early specialist referral optimizes the timing and choice of surgical intervention
Frequently Asked Questions About Patellar Luxation in Dogs
What is patellar luxation in dogs?
Patellar luxation is a condition in which the kneecap (patella) slips out of the femoral trochlear groove in which it normally rides. It is caused by a developmental skeletal malalignment that is typically inherited. It is graded I through IV based on severity: Grade I is manually luxatable only; Grade II luxates spontaneously but self-reduces (classic skipping gait); Grade III is permanently luxated but manually reducible; Grade IV is permanently luxated and not reducible. It is one of the most common orthopedic conditions in dogs, especially small and toy breeds.
What does patellar luxation look like in a dog?
The most recognizable sign is the intermittent “skipping” gait of Grade II disease: the dog suddenly holds up one rear leg for 1 to 4 steps while walking or running, sometimes shakes or stretches the leg, then resumes normal gait when the patella snaps back into place. Grade III to IV disease produces persistent lameness, a crouched gait, and muscle atrophy. Many Grade I dogs show no symptoms at all. Both rear legs are often affected, though usually one side is worse.
Does patellar luxation require surgery?
Surgery is recommended for Grade II dogs with frequent lameness, all Grade III to IV dogs, and dogs with concurrent CCL rupture. Grade I and mild Grade II dogs with infrequent lameness can be managed medically with weight management, low-impact exercise, NSAIDs for flare-ups, and joint supplements. Medical management does not correct the underlying malalignment or prevent articular cartilage wear; Grade II dogs managed conservatively for years often progress to Grade III and develop secondary osteoarthritis.
What is the success rate of patellar luxation surgery in dogs?
More than 90 percent of Grade II to III dogs undergoing standard patellar luxation surgery (trochlear recession plus tibial tuberosity transposition) return to good or excellent function within 8 to 12 weeks. Re-luxation occurs in approximately 10 to 20 percent of Grade III cases and a smaller proportion of Grade II cases. Grade IV cases and those requiring corrective osteotomy have more variable outcomes. Bilateral surgeries (both stifles) are often staged 6 to 8 weeks apart to allow one leg to recover enough to bear weight before the other is operated.
Can patellar luxation cause cruciate ligament rupture?
Yes. Grade II and higher medial patellar luxation significantly increases the risk of cranial cruciate ligament (CCL) rupture in the same stifle, because the skeletal malalignment that causes the patella to luxate also creates abnormal shear and rotational forces on the CCL. Dogs with MPL are 3 to 4 times more likely to rupture their CCL than dogs without MPL. A dog with both conditions needs both corrected surgically at the same time; repairing only the CCL while leaving the patellar luxation uncorrected leads to higher rates of CCL repair failure.
What breeds are most prone to patellar luxation?
Toy and small breeds have the highest risk, including Yorkshire Terrier, Chihuahua, Pomeranian, Toy and Miniature Poodle, Maltese, Bichon Frise, Boston Terrier, and Miniature Pinscher. French Bulldogs also have high incidence. Large breeds are affected less commonly, with Labrador Retrievers, Flat-coated Retrievers, and Boxers at elevated risk for lateral patellar luxation. The condition is strongly hereditary; breeding dogs with Grade II or higher patellar luxation is discouraged.
How long does recovery from patellar luxation surgery take?
Recovery from standard patellar luxation surgery in a small dog (trochlear recession plus tibial tuberosity transposition) takes approximately 8 to 12 weeks for full return to normal activity. The first 6 to 8 weeks require strict rest and leash walks only. Physical rehabilitation with underwater treadmill and range of motion exercises from weeks 4 to 12 accelerates recovery and reduces muscle atrophy. Most small dogs are walking well on the operated limb within 2 to 3 weeks of surgery. Complex cases involving corrective osteotomy take 12 to 20 weeks.
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