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Diagnostics2026-07-25 · 19 min read

Patellar Luxation in Dogs: The 4 Grades, Skipping Gait, and Surgery Decisions

Patellar luxation causes the classic skipping gait in dogs, especially small breeds. Learn the 4 grades, conservative management limits, surgery success rates, and staged cost realities.

Ran Chen
Ran Chen
Founder, VetMedGuide. Life-sciences operator and 10× global market-access lead.
Published

An owner of a small-breed dog — such as a Yorkshire Terrier, Pomeranian, Toy or Miniature Poodle, Chihuahua, Boston Terrier, French Bulldog, or Pug — often witnesses a peculiar behavior on walks. Their dog is trotting along normally, suddenly "skips" or holds a hind leg up for three or four strides, and then, just as suddenly, kicks the leg straight out behind them, pops it back down, and resumes walking as if nothing happened.

This classic, intermittent "skipping gait" is the hallmark sign of a luxating patella (a kneecap that pops out of its groove). For many owners, the initial reaction is confusion, which turns to concern when a veterinarian performs an orthopedic palpation, diagnoses patellar luxation, and begins discussing potential surgery, chronic weight management, and anti-inflammatory medications.

Owners are immediately faced with difficult questions: What exactly is a luxating patella, and is it a serious threat to my dog’s quality of life? What do the four different grades mean, and is surgery really necessary for a dog that seems to recover in a few seconds? What are the surgical success and complication rates, and what does it cost? Furthermore, how does this condition lead to progressive arthritis or increase the risk of a torn cranial cruciate ligament (CCL)?

This guide provides a comprehensive clinical and practical breakdown of canine patellar luxation to help veterinary professionals guide clients, and to help owners make informed decisions about their dog's orthopedic care.

What is a luxating patella, and why do small dogs get the skipping gait?

To understand patellar luxation, one must first look at the anatomy of the canine stifle (knee) joint. The patella (kneecap) is a small, almond-shaped bone embedded within the tendon of the quadriceps muscle group. Under normal conditions, the patella slides smoothly up and down within a vertical cartilage-lined channel called the femoral trochlear groove, located at the front of the distal femur (thigh bone). The patella acts as a pulley, redirecting the pull of the quadriceps muscle to the crest of the tibia (shin bone) via the patellar ligament, allowing the dog to extend the stifle and walk.

Patellar luxation occurs when the patella slips out of this trochlear groove, sliding either to the inside of the knee (medial patellar luxation, or MPL) or to the outside (lateral patellar luxation, or LPL).

The anatomical cascade

In the vast majority of small and toy-breed dogs, patellar luxation is a developmental, congenital condition, rather than the result of acute trauma. It is caused by a progressive misalignment of the entire extensor mechanism of the hind limb. This misalignment typically involves:

  1. Coxa vara and femoral varus: An abnormal inward bowing or curvature of the femur (thigh bone).
  2. Shallow trochlear groove: Because the patella does not sit firmly and consistently in its groove during skeletal development, the groove fails to develop sufficient depth, remaining shallow or even flat.
  3. Tibial tuberosity deviation: The bony attachment point of the patellar ligament on the shin bone (the tibial tuberosity) is rotated inward (medially) relative to the femur.
  4. Quadriceps pull deviation: As a result of these bony deviations, the entire pull of the quadriceps muscle group is directed medially. This exerts a constant inward force on the patella, pulling it over the medial trochlear ridge.

When the patella slips out of the groove, the stifle joint is mechanically locked in a partially flexed position. The dog cannot comfortably put weight on the leg, leading to the classic "skipping" behavior. The dog holds the leg up until the quadriceps muscle relaxes or the dog extension-kicks the leg, allowing the patella to pop back over the trochlear ridge and slide back into the groove.

Medial vs. lateral luxation

  • Medial Patellar Luxation (MPL): This is by far the most common form, accounting for roughly 75% to 90% of all canine patellar luxation cases. It predominantly affects toy, miniature, and small dog breeds.
  • Lateral Patellar Luxation (LPL): LPL is relatively more common in large and giant dog breeds (such as Great Danes, Saint Bernards, and Irish Wolfhounds), often associated with femoral valus (knock-kneed conformation) and external rotation of the tibia. However, it can occasionally occur in toy breeds.

The four grades of patellar luxation (Putnam)

Veterinarians grade the severity of patellar luxation using the Putnam grading system (originally described in 1968). This classification scale, ranging from Grade I to Grade IV, is based on how easily the patella can be luxated during an orthopedic exam, whether it reduces (returns to the groove) spontaneously, and the degree of associated bone deformity.

Grade Physical Characteristics on Exam Typical Clinical Signs & Gait Primary Treatment Approach
Grade I The patella can be manually pushed out of the groove but pops back in spontaneously as soon as pressure is released. Often completely asymptomatic; no skipping or lameness; typically found incidentally during routine vet exams. Conservative management (monitoring, weight control, joint support). Surgery is almost never indicated.
Grade II The patella luxates spontaneously during stifle flexion or manual pressure, and remains out until the joint is extended or manually replaced. Intermittent skipping gait; holding the leg up for a few steps, then kicking it out to reset the kneecap. Symptomatic dogs: Surgery. Asymptomatic dogs: Conservative management with close monitoring.
Grade III The patella remains permanently luxated out of the groove, but can be manually pushed back in. Once manual pressure is released, it immediately re-luxates. Persistent or frequent lameness; a slightly crouched gait; stiffness; reluctance to jump. Surgical correction is strongly recommended to prevent severe arthritis and permanent deformity.
Grade IV The patella is permanently luxated and cannot be manually reduced. The trochlear groove is flat or convex, and there is severe rotational deformity of the lower limb. Persistent crouched or "crab-like" gait; inability to fully extend the knee; significant muscle wastage (atrophy). Surgical correction is highly complex and required to restore basic mobility, often requiring corrective bone cuts.

How is patellar luxation diagnosed?

A definitive diagnosis of patellar luxation requires a thorough orthopedic examination, supplemented by diagnostic imaging.

The orthopedic examination

During the physical exam, a veterinarian will palpate the stifle joint with the dog standing and lying down. The clinician will flex and extend the stifle while internally and externally rotating the paw to assess the stability of the patella.

It is critical during this exam to perform a comprehensive stifle assessment, specifically evaluating the cranial cruciate ligament (CCL). The veterinarian will check for "cranial drawer" and "cranial tibial thrust" — tests where the femur and tibia are manipulated to see if the tibia slides forward abnormally. Because patellar luxation and CCL tears frequently coexist, identifying ligamentous instability early is vital for accurate surgical planning.

Radiography (X-rays)

Orthogonal radiographs (viewed from the side and from front-to-back) of the entire pelvis and hind limbs are standard. Radiographs are used to:

  • Confirm the direction of the luxation (medial vs. lateral).
  • Assess the degree of osteoarthritis (bone spurs, joint effusion, subchondral bone thickening).
  • Check the position of the tibial tuberosity.
  • Screen for femoral varus or tibial torsion.

Advanced imaging (CT scans)

For dogs with Grade IV luxation, or those with severe Grade III deformity, a three-dimensional computed tomography (CT) scan is increasingly recommended. A CT scan allows the veterinary surgeon to precisely measure the angles of femoral varus and tibial torsion. This data is used to plan corrective osteotomies (bone-cutting procedures) to straighten the limb, which is crucial for preventing surgical failure in severe cases.

Grade by grade: conservative management vs. surgery

The optimal treatment path for a dog with a luxating patella is determined primarily by the clinical grade of the condition and whether the dog is experiencing pain or functional impairment.

Grade I

Grade I dogs are typically diagnosed incidentally. They do not skip, show lameness, or have difficulty running.

  • The approach: Conservative management. Surgery is not indicated for Grade I dogs. The goal is to maintain a lean body condition and monitor the knee during annual wellness exams.

Grade II

Grade II represents the most diverse clinical group. Some Grade II dogs skip once every few weeks and show no joint pain, while others skip multiple times a day, limp frequently, and exhibit discomfort during veterinary manipulation.

  • The approach: If a Grade II dog is asymptomatic or has very mild, infrequent clinical signs, conservative management is appropriate. However, if the dog is showing frequent lameness, pain, or a progressive worsening of the gait, surgical correction is recommended. Surgery is performed to prevent the onset of severe, irreversible osteoarthritis and to protect the cruciate ligament.

Grade III & Grade IV

Permanent luxation alters the mechanical alignment of the leg, putting abnormal, continuous forces on the joint cartilage and surrounding ligaments.

  • The approach: Surgical correction is strongly recommended for Grade III and Grade IV cases. Without surgery, these dogs will develop progressive, painful osteoarthritis, joint contracture, and rotational limb deformities that severely limit mobility.

The conservative management toolbox

When managing low-grade or asymptomatic patellar luxation, or supporting a dog that is not a candidate for anesthesia, a multimodal conservative approach is utilized.

1. Strict weight management

This is the single most important non-surgical intervention. Excess body weight increases the force placed on the stifle joint and amplifies the pull of the quadriceps muscle group, making it easier for the patella to slip over the trochlear ridge. Maintaining a dog at a Body Condition Score (BCS) of 4 out of 9 (slightly lean) significantly reduces joint stress and chronic inflammatory markers.

2. Targeted rehabilitation and exercise

High-impact activities that involve sudden turning, pivoting, or jumping (such as chasing balls or playing frisbee) should be limited. Instead, focus on controlled, low-impact exercise (such as leash walking and controlled swimming) to build the quadriceps and hamstring muscles. Strengthening these muscle groups helps stabilize the patella within the groove. Physical rehab exercises, such as sit-to-stands and balance paw-touches, are highly beneficial.

3. Joint supplements

Supplements such as glucosamine, chondroitin sulfate, omega-3 fatty acids (EPA/DHA), and green-lipped mussel help support cartilage health, improve synovial fluid quality, and reduce mild joint inflammation.

4. The veterinary NSAID ladder

For dogs experiencing occasional flares or periods of lameness, non-steroidal anti-inflammatory drugs (NSAIDs) are prescribed under veterinary supervision. NSAIDs reduce joint pain and inflammation, allowing the dog to remain active and maintain muscle mass.

According to pharmacovigilance data from the FDA Center for Veterinary Medicine (CVM) animal drug adverse-event database (aggregated as of July 2026), the following veterinary NSAIDs and analgesics form the primary therapeutic options, listed with their total reported adverse-event footprint:

  • Carprofen: 51,388 reports (The most widely prescribed veterinary NSAID; highly effective for perioperative and chronic osteoarthritis pain).
  • Meloxicam: 17,042 reports (Commonly used liquid NSAID, allowing precise dosing).
  • Deracoxib: 11,958 reports (Chewable tablet, frequently used for post-operative pain).
  • Grapiprant: 8,212 reports (A non-cyclooxygenase-inhibiting NSAID that targets the EP4 receptor specifically, often selected for dogs with renal or hepatic compromise).
  • Firocoxib: 7,725 reports (A highly selective COX-2 inhibitor).
  • Robenacoxib: 3,371 reports (Mainly used in acute pain; available as tablets and injection).
  • Etodolac: 1,945 reports (An older veterinary NSAID).
  • Tepoxalin: 1,166 reports (An older agent, largely discontinued).

[!IMPORTANT] Adverse-Event Reporting Caveat: These raw openFDA numbers represent the total historical volume of reported adverse-event mentions. They reflect overall prescribing frequency and drug usage volume rather than a direct measure of drug toxicity or head-to-head comparative safety. For example, the high count for carprofen reflects its decades-long status as the market-leading canine NSAID, not a higher inherent risk. All veterinary NSAIDs require baseline blood work and regular hepatic and renal monitoring.

[!CAUTION] Human NSAID Warning: Never give human over-the-counter pain medications, such as ibuprofen (Advil, Motrin), naproxen (Aleve), or aspirin, to a dog. These drugs have a very narrow margin of safety in dogs and frequently cause life-threatening gastrointestinal ulceration, acute renal failure, and liver damage.

What does patellar luxation surgery involve?

Surgical correction of patellar luxation is structural. The goal is to rebuild the knee joint so that the quadriceps, patella, and tibia are aligned in a straight line. To achieve this, a veterinary surgeon will combine several surgical techniques:

1. Trochleoplasty (Deepening the groove)

The surgeon must deepen the shallow femoral groove. The preferred technique is a trochlear block recession or trochlear wedge recession. The surgeon cuts a wedge- or block-shaped piece of bone and cartilage out of the groove, removes a layer of underlying bone underneath it, and replaces the cartilage wedge. This sinks the groove deeper into the femur while preserving the vital articular cartilage surface.

2. Tibial Tuberosity Transposition (TTT)

To correct the inward rotation of the lower leg, the surgeon performs a TTT. The tibial tuberosity (the bony ridge where the patellar tendon attaches) is cut free from the shin bone, slid laterally (outward) to line up with the femoral groove, and pinned into its new position using orthopedic pins and tension-band wires.

3. Soft-Tissue Rebalancing

The tissues on the side of the knee that the patella slipped toward are stretched and tight, while the tissues on the opposite side are stretched and loose. The surgeon performs a lateral imbrication (tightening the loose tissues on the outside) and a medial release (incising the tight joint capsule on the inside) to balance the tension.

4. Corrective Femoral Osteotomy

In severe Grade IV cases with marked bone deformity, the surgeon must cut the femur, remove a calculated wedge of bone to straighten the thigh bone, and stabilize it with an orthopedic plate and screws.

[Normal Knee]            [Medial Luxation (MPL)]          [Surgical Fix]
  Femur                     Femur                           Femur
  |   | (Deep Groove)       |   | (Shallow/Flat)            |===| (Deepened Groove)
  | o | (Patella centered)    o   | (Patella slipped in)    | o | (Patella centered)
  |   |                     |   |                           |   |
  Tibia                     Tibia                           Tibia
  | |                       \ \ (Rotated inward)            | | (Tibial ridge moved lateral)

Success and complication rates

  • Success rate: Multiple peer-reviewed studies (such as Di Dona et al. 2018, PMC6055913) report that roughly 90% of owners report good-to-excellent outcomes following surgery, with a return to normal or near-normal limb function and resolution of lameness.
  • Complication rate: Surgical complications occur in approximately 10% to 18% of cases. The most common complications include:
    • Surgical site infection: Managed with antibiotics.
    • Pin migration or irritation: The orthopedic pins used in the TTT can back out or irritate the skin, requiring removal once the bone has fully healed.
    • Patellar re-luxation: In a small percentage of cases (usually Grade III or IV), the patella may slip out of the groove again, sometimes requiring a revision surgery.
    • Tibial tuberosity avulsion: The bone ridge fracture failing to heal or pulling away.

Why a luxating patella leads to arthritis and cruciate (CCL) tears

Patellar luxation is not merely a cosmetic issue; it alters the biomechanics of the stifle joint, leading to progressive damage.

The slide into osteoarthritis

Every time the patella slips out of its groove, it grinds over the trochlear ridge. This mechanical abrasion erodes the smooth articular cartilage, exposing the underlying subchondral bone. This bone-on-bone friction triggers chronic joint inflammation, leading to the development of osteophytes (bone spurs) and joint capsule thickening. Once osteoarthritis begins, it cannot be reversed. The goal of early surgical intervention in symptomatic dogs is to halt or drastically slow this progression.

The cruciate ligament (CCL) connection

The cruciate ligaments are the primary stabilizers inside the dog's knee. In a dog with medial patellar luxation, the inward pull of the quadriceps muscle places a continuous rotational force on the tibia, twisting the knee joint inward. This abnormal rotation puts significant, chronic shear stress on the cranial cruciate ligament.

Over time, this continuous micro-strain weakens the CCL, leading to progressive tearing. Clinical studies indicate that approximately 13% to 25% of dogs with medial patellar luxation will develop a concurrent CCL rupture in the same knee. In small breeds, this rate can be even higher. When this occurs, the surgeon must perform both a patellar stabilization and a cruciate (CCL) repair in the same procedure, which increases surgical complexity, cost, and recovery time.

How much does surgery cost, and what is the recovery?

Surgical costs

The cost of patellar luxation surgery varies widely based on the dog's size, the severity of the deformity, geographic location, and whether the procedure is performed by a general practitioner or a board-certified veterinary surgeon (DACVS).

  • Unilateral (One Leg) Surgery:
    • General Practitioner: $1,200 to $2,500 per leg.
    • Board-Certified Specialist: $3,000 to $5,500 per leg (includes advanced diagnostics, specialized anesthesia monitoring, and post-operative care).
  • Bilateral (Both Legs) Surgery: If both knees are affected, the cost of staging the surgeries separately is higher. However, under certain conditions, both knees can be corrected during a single anesthetic event.

Single-session bilateral surgery economics

In a landmark retrospective study (Fullagar et al. 2017, PMC5157736), researchers compared unilateral, staged-bilateral, and single-session-bilateral surgery for bilateral MPL across 119 stifles. The single-session bilateral subgroup consisted entirely of dogs under 10 kg. The study concluded that dogs under 10 kg undergoing single-session bilateral surgery had a complication rate comparable to those undergoing staged or unilateral procedures — an overall complication rate of 24% (28/119 stifles) with major complications requiring revision in 9% (11/119 stifles), with no significant association between the timing of surgery and complications.

Fixing both knees at once:

  • Cuts the total anesthetic events from two to one.
  • Reduces the total recovery period from 12–16 weeks (staged) to a single 8-week period.
  • Lowers total cost by eliminating duplicate surgical prep, anesthesia, and hospitalization fees (often saving $1,000 to $2,000 compared to staged procedures).

For small dogs, this is often the most compassionate and cost-effective route, provided the owner can dedicate the time to manage a dog with two healing hind legs.

The recovery timeline

Post-operative recovery typically takes 6 to 8 weeks and requires strict confinement:

  • Weeks 1–2: Strict crate confinement. The dog is allowed out only on a short leash for brief, controlled bathroom breaks. Pain management (NSAIDs plus gabapentin) is critical. Absorbable sutures are monitored, and local ice packing is performed.
  • Weeks 3–4: Continued crate confinement. The veterinarian may authorize short, 5-minute leash walks on flat surfaces. Controlled range-of-motion exercises may begin.
  • Weeks 5–6: Follow-up radiographs are taken to verify bone healing at the cut tibial tuberosity. If the bone is healing well, leash walks are gradually increased to 10–15 minutes.
  • Weeks 7–8: Gradual return to normal activity. Leash walks are extended, but off-leash running and jumping are still restricted until full clearance is given by the surgeon.

Frequently Asked Questions

Can a dog live with a luxating patella without surgery?

Yes. Many dogs with Grade I and mild, asymptomatic Grade II patellar luxation live long, comfortable lives without surgery. This is achieved through strict weight control, joint supplements, and regular low-impact exercise to maintain muscle strength. However, dogs with symptomatic Grade II, or Grades III and IV, will suffer from chronic pain, muscle wastage, and severe arthritis if left untreated.

How much does it cost to fix a luxating patella in dogs?

The cost generally ranges from $1,200 to $2,500 per leg at a general practice, and $3,000 to $5,500 per leg at a board-certified veterinary surgeon. If both legs are corrected at once in a small dog (under 10 kg), the total cost is often reduced.

What are the four grades of patellar luxation?

  • Grade I: The kneecap can be manually pushed out of place but pops back in on its own.
  • Grade II: The kneecap slips out of place during movement and stays out until the leg is straightened or pushed back.
  • Grade III: The kneecap sits out of place permanently but can be pushed back in manually.
  • Grade IV: The kneecap is out of place permanently and cannot be pushed back in, even manually, due to bone deformities.

How long does it take a dog to recover from patellar luxation surgery?

It takes approximately 6 to 8 weeks of strict crate confinement and leash-only walks. Post-operative X-rays at week 6 are required to confirm that the cut bone has fully healed before the dog is allowed to gradually resume normal activity.

Does a luxating patella cause arthritis or a torn CCL later?

Yes. The rubbing of the displaced kneecap erodes joint cartilage, inevitably leading to osteoarthritis. Additionally, the abnormal twisting force on the knee joint puts chronic stress on the cranial cruciate ligament (CCL), resulting in a concurrent CCL tear in 13% to 25% of affected dogs.

Sources

Topics
Canine Osteoarthritis
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