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Unilateral vs. Bilateral Medial Patellar Luxation in Dogs

Unilateral vs. Bilateral Medial Patellar Luxation in Dogs

Medial Patellar Luxation

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Compare unilateral vs. bilateral medial patellar luxation in dogs—symptoms, treatment, surgery options, and recovery differences explained simply

By 

Sustainable Vet Group

Updated on

July 28, 2025

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Unilateral vs. Bilateral Medial Patellar Luxation in Dogs

What Is Medial Patellar Luxation (MPL)?

Medial Patellar Luxation (MPL) is a condition where a dog’s kneecap slips out of its normal position, usually toward the inside of the leg.

In a healthy knee, the patella (kneecap) sits in a groove on the thigh bone and moves smoothly as the leg bends. With MPL, the kneecap moves out of place, causing the joint to become unstable. This can lead to limping, pain, or an unusual gait.

MPL is most often congenital, meaning a dog is born with it. It may also develop from poor skeletal alignment or trauma to the knee. It’s common in small breeds like Pomeranians, Chihuahuas, and Poodles, but it can also affect large breeds like Labradors or Great Pyrenees.

MPL is graded by severity:

  • Grade I: Occasional luxation
  • Grade II: Frequent but returns on its own
  • Grade III: Constant but manually correctable
  • Grade IV: Permanently out and not correctable manually

Understanding the grade helps guide treatment.

Unilateral vs. Bilateral MPL: What’s the Difference?

Some dogs have MPL in one knee (unilateral), while others have it in both knees (bilateral). The difference matters for treatment, recovery, and long-term health.

  • Unilateral MPL affects only one knee, often showing signs like limping or skipping on a single limb.
  • Bilateral MPL means both knees are unstable, leading to crouched posture, bunny-hopping, or bow-legged gait.
  • Around 50% of dogs diagnosed with MPL have both knees involved.
  • Even if only one knee shows symptoms now, the other may develop problems later.
  • Dogs may be born with both knees affected or develop the second case over time.

Knowing whether MPL is unilateral or bilateral helps you and your vet plan treatment. Surgery decisions, home recovery setup, and rehab routines may differ.

Your vet will examine both knees, even if only one looks painful, to catch early signs. Treating both knees at once can be harder short term but may reduce future complications. Monitoring both knees is important, no matter which type your dog has.

Read more | Grade 2 Medial Patellar Luxation: Surgery Decision Guide

Symptoms Comparison in Unilateral vs. Bilateral Cases

The signs of medial patellar luxation (MPL) can differ depending on whether one or both knees are affected. Understanding these differences helps in faster recognition and proper care.

Unilateral MPL usually causes signs in one back leg. You might notice:

  • Limping or skipping on the affected limb
  • Sudden return to normal gait after skipping
  • Less weight-bearing on one side

Bilateral MPL tends to affect the dog’s posture and overall movement more visibly:

  • Bunny-hopping when running
  • Crouched stance or stiffness in both legs
  • Bow-legged posture, especially in small breeds

In both cases, you may see behavioral changes such as reduced play, unwillingness to go on walks, or hesitation to jump. Often, dogs compensate by using the stronger leg more, which can hide the issue for a while. That’s why many unilateral cases go unnoticed until the second knee shows signs.

Early signs are often subtle, so regular observation of how your dog moves is key. Watch for changes in rhythm, posture, or hesitation during movement. Prompt evaluation helps in catching the condition early—before the second knee becomes involved or symptoms worsen.

Read more | How to Prevent Medial Patellar Luxation in Puppies

Diagnosis and Imaging for One or Both Knees

Vets use hands-on exams and imaging to confirm MPL and check whether one or both knees are involved. Diagnosis is important to plan treatment and avoid future issues.

During the physical exam, your vet will:

  • Feel the kneecap for looseness or misalignment
  • Apply pressure to assess luxation and assign a grade (I to IV)
  • Observe your dog’s gait for limping, skipping, or stance changes

Each knee is graded separately. Even if signs appear in one leg, both knees are always checked. Around half of MPL cases affect both knees, so early diagnosis can guide preventive care for the other side.

Radiographs (X-rays) may also be recommended:

  • Help evaluate bone alignment and shape
  • Detect signs of joint wear or arthritis
  • Rule out fractures or other problems

In some cases, advanced imaging (like CT scans) may be used for surgical planning. Diagnosis isn’t just about confirming MPL—it’s about understanding the extent and making the best plan for treatment. Whether surgery is needed or not, knowing both knees’ condition helps avoid surprises later.

Read more | Medial Patellar Luxation in Small vs. Large Dogs

Surgical Options: Treating One or Both Knees

Surgery is often needed when MPL causes pain or affects movement. The decision to operate on one or both knees depends on symptoms, severity, and the dog’s overall condition.

Unilateral Surgery

  • Recommended when only one knee shows signs
  • Less intense recovery since one leg stays stable
  • If the second knee worsens later, surgery can be done separately
  • Helps dogs return to normal activity with fewer risks

Bilateral Surgery

  • Done when both knees are affected or if one is borderline
  • Can be performed at once (simultaneous) or one after another (staged)
  • Offers long-term relief and cost savings when done together
  • Slightly tougher recovery since both legs are healing

Most dogs recover well from either approach. The choice depends on vet advice, owner ability to manage post-op care, and how the dog is handling its current condition. Many vets prefer to treat both knees if symptoms exist, to avoid multiple surgeries and extended downtime.

Read more | Best Exercises and Rehab for Dogs After MPL Surgery

Pros and Cons of Bilateral vs. Unilateral Surgery

Owners often wonder whether fixing one knee or both is better. Each option has trade-offs in terms of cost, recovery, and long-term outcomes.

Bilateral Surgery Pros

  • One anesthesia event instead of two
  • Single recovery period with no second surgery later
  • Often more cost-effective overall

Bilateral Surgery Cons

  • Harder for dogs to walk during early healing
  • May require more hands-on care (sling walking, crate rest)
  • Slightly increased risk of surgical stress

Unilateral Surgery Pros

  • Easier recovery using the healthy leg for support
  • Less intensive aftercare
  • Good for mild or first-time cases

Unilateral Surgery Cons

  • Second knee may need surgery later
  • Total recovery timeline could be longer
  • Dogs may overuse healthy leg, causing strain

Choosing depends on your dog’s health, the vet’s opinion, and your ability to manage care. Discuss risks and benefits openly with your vet so you’re prepared for either scenario.

Read more | Medial Patellar Luxation Treatment Without Surgery

Long-Term Outlook and Risk of Progression

Understanding the long-term effects of unilateral and bilateral MPL is key to managing your dog’s mobility and comfort. Even if only one knee is affected now, there’s a strong chance the other may show symptoms later.

For unilateral MPL:

  • Many dogs develop issues in the second knee within months or years
  • Overuse of the healthy leg may cause early joint wear
  • Ongoing monitoring is needed to catch problems early

For bilateral MPL:

  • Dogs treated for both knees often enjoy better balance and long-term comfort
  • Posture and gait return to normal faster
  • Risk of progression is lower once both knees are stabilized

Dogs with Grade I or II luxation may live comfortably with exercise control and monitoring, but higher grades often require surgery to prevent worsening. Without treatment, MPL can lead to joint damage, arthritis, or permanent mobility issues.

Early intervention, whether surgical or not, helps preserve quality of life and joint health. Work closely with your vet to reassess alignment and gait during routine visits. Catching changes early often leads to easier, less invasive treatment and fewer complications.

Read more | How to Tell If Your Dog Has a Medially Luxating Patella

Post-Operative Care: What Differs by Type

Recovery after MPL surgery is slightly different for unilateral and bilateral cases. The basic care principles stay the same, but the intensity and support required can vary.

For unilateral surgery:

  • Dogs often manage with one strong leg
  • Shorter duration of assisted walking
  • Faster return to weight-bearing activity

For bilateral surgery:

  • May need help walking for the first 7–10 days
  • Use of a sling or harness is common
  • Physical therapy is often more intensive

Key aspects of post-op care for both:

  • Restricted activity for 6–8 weeks
  • Controlled leash walks to rebuild strength
  • Passive range-of-motion exercises (if advised)
  • Pain management and anti-inflammatories
  • Preventing access to stairs or jumping surfaces

Recovery timelines vary by dog, but many show big improvements by week 4. It’s important to follow your vet’s timeline closely. Skipping steps or increasing activity too fast can cause setbacks.

Bilateral cases may feel harder early on, but both types require patience and consistency to achieve full healing and normal movement.

Read more | Recovery After Medial Patellar Luxation Surgery in Dogs

Owner Considerations When Choosing Surgery Type

Choosing between unilateral and bilateral MPL surgery depends on more than just vet advice. Your lifestyle, budget, and support system also matter when planning for your dog’s recovery.

Key things to consider:

  • Care support: Can someone help with sling walking or lifting?
  • Budget: Bilateral surgery may cost more upfront but saves on future anesthesia and follow-up visits.
  • Time: One recovery period vs. two separate ones
  • Home setup: Stairs, slippery floors, and crate space all play a role
  • Dog's comfort: Some dogs do better when both knees are treated together, while others need a slower approach

Your vet will guide you based on your dog’s health and luxation grade. But your role in daily care is just as important. If you work long hours or have limited help at home, staged unilateral surgeries may be easier to manage.

On the other hand, if your dog is struggling with both legs, doing both at once may offer quicker overall relief. Think about the long run—not just the surgery day.

Monitoring for Changes in the Opposite Knee

Even if your dog only has MPL in one leg now, the other knee may be at risk too. Keeping a close eye on gait and posture helps you catch early signs before things get worse.

Watch for these signs in the “healthy” leg:

  • Skipping, limping, or toe-touching
  • Slower movement or hesitation to climb stairs
  • Shifting weight to one side
  • Bunny-hopping gait during fast movement

Regular rechecks are important. Your vet may perform:

  • Physical exams to grade luxation
  • X-rays to check bone angles and joint wear
  • Gait assessments to spot compensation or early imbalance

Home videos of your dog walking can also help detect changes between visits. If the second knee begins to show signs, treatment can start early, often avoiding a crisis. Early detection helps prevent cartilage damage, arthritis, or falls from instability.

Stay proactive even after surgery. The second knee might stay stable, but many dogs eventually need care for both legs. Monitoring ensures you act before the issue becomes painful or limits movement.

Read more | Signs and Symptoms of Medial Patellar Luxation in Dogs

Final Thoughts: Which Option Is Better?

There’s no single “best” option—unilateral or bilateral MPL surgery both have value depending on your dog’s situation. What matters most is tailoring the approach to your dog’s needs and your ability to manage recovery.

Choose unilateral if:

  • Only one knee is affected
  • You prefer an easier recovery process
  • You want to space out costs and care time

Choose bilateral if:

  • Both knees show symptoms or have high-grade luxation
  • Your dog struggles with movement or posture
  • You want to avoid two anesthesia events and staggered healing

Many dogs thrive after either route when post-op care is done right. The goal isn’t just to fix the knee, it’s to restore comfort, prevent joint damage, and let your dog enjoy normal play again.

Trust your vet’s assessment and be honest about your home setup. Either way, early treatment and steady follow-through give your dog the best shot at a full, active life.

FAQs

Is it common for unilateral MPL to become bilateral?

Yes, it’s quite common. Many dogs diagnosed with unilateral medial patellar luxation eventually develop it in the other knee. This is especially true in small breeds or dogs with poor limb alignment. The added stress on the unaffected leg can speed up the problem. Regular vet checks help catch early signs so you can plan treatment before the second knee worsens or becomes painful.

Can both knees be operated on at the same time?

Yes, both knees can be treated in one surgical session, especially if both are symptomatic or have high-grade luxation. Many vets recommend bilateral surgery when the dog struggles to walk or stand properly. Recovery may be more intense at first, but long-term healing is faster. Your vet will consider age, overall health, and your ability to support the recovery process before recommending this approach.

Which surgery has a faster recovery—unilateral or bilateral?

Unilateral surgery often feels easier in the short term. The dog can rely on the healthy leg during early recovery, making movement and care simpler. Bilateral surgery may look harder at first but can shorten overall recovery by addressing both knees at once. If managed carefully with support and rehab, dogs recover well from either surgery type and return to normal activity with proper care.

Is bilateral MPL more painful or severe?

Bilateral MPL can cause more discomfort and instability than unilateral cases because both knees lack support. Dogs may show more signs of lameness, awkward walking, or reluctance to move. Surgery for both knees can cause more soreness early on, but pain is well controlled with medication. Once healed, dogs often regain better balance and comfort compared to treating just one knee at a time.

What if only one knee shows symptoms?

Even if just one knee shows signs, the other may be affected mildly or start developing changes later. Your vet will check both knees during the exam to assess risk. If the second knee is stable, your dog may only need unilateral treatment. However, keep monitoring the other leg. Early signs like skipping or shifting weight may mean it’s time to discuss further care.

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