The Ultimate Guide to Partial Knee Replacement

When Less Really Is More: A Path Forward for Single-Compartment Knee Arthritis

Sarah had always been active—hiking on weekends, playing tennis with friends, walking her dog through her neighborhood. But over the past two years, her right knee had become increasingly painful, particularly on the inner side. She visited her primary care physician, tried physical therapy, injections, and anti-inflammatory medications. Nothing provided lasting relief.

When she finally saw an orthopedic surgeon, she received news that shook her: "You need a total knee replacement."

Sarah wasn't ready to accept that her only option was to remove and replace the entire knee joint—a major surgery with months of rehabilitation ahead. She wanted to know if there was something less invasive, something that would preserve more of her natural knee while addressing her pain.

That's when she learned about partial knee replacement, and her perspective on her future changed completely.

If you're facing a similar diagnosis—hearing that your knee arthritis might require surgery—this guide will help you understand whether partial knee replacement might be the right path for you. Dr. Andrew Wassef, MD, an orthopedic surgeon specializing in joint replacement at Commons Clinic, walks us through everything you need to know about this increasingly popular procedure.

What Is Partial Knee Replacement?

The human knee is a sophisticated joint made up of three distinct compartments:

• Medial compartment — the inner side of the knee
• Lateral compartment — the outer side of the knee
• Patellofemoral compartment — the area between the kneecap and thighbone

Osteoarthritis often doesn't affect the entire knee equally. In many patients, arthritis is concentrated in just one compartment, while the other two compartments remain relatively healthy with intact cartilage, bone, and ligaments.

This is where partial knee replacement—also called unicompartmental arthroplasty (UKA)—becomes an excellent option.

Unlike a total knee replacement (TKR), which removes and replaces bone surfaces across all three compartments, a partial knee replacement surgically addresses only the damaged compartment. The procedure involves:

1. Making a smaller surgical incision (typically 3-4 inches compared to 8-10 inches for total knee replacement)
2. Removing only the damaged bone and cartilage from the affected compartment
3. Preserving healthy bone, cartilage, and ligaments in the other two compartments and throughout the knee
4. Placing a custom implant sized and positioned to restore smooth joint function in that single compartment

Because the procedure preserves so much of your natural knee anatomy, many patients report that their knee feels more natural after recovery compared to a total knee replacement.

When Should You Consider Partial Knee Replacement?

Partial knee replacement isn't appropriate for everyone with knee arthritis, but it's an excellent option if you meet specific criteria:

Ideal Candidates Include:

Single-Compartment Arthritis Your arthritis is isolated to one compartment, with minimal or no degeneration in the other two compartments. Imaging (X-rays and sometimes MRI) confirms this pattern.

Intact ACL (Anterior Cruciate Ligament) Your anterior cruciate ligament is functional and healthy. The ACL provides crucial stability to the knee, and its presence is essential for partial knee replacement success. If your ACL is torn, you'll typically need a total knee replacement instead.

Correctable Deformity If you have any knee malalignment (bowlegged or knock-kneed appearance), it must be correctable—meaning it can be addressed during the partial knee replacement procedure. Severe, fixed deformities may require a total knee replacement.

Age Considerations While there's no strict age cutoff, partial knee replacement works particularly well for patients aged 50-75. Younger patients may face higher lifetime revision rates due to implant wear over decades. Older patients may have other medical concerns that make them better candidates for the less extensive procedure.

BMI Considerations Patients with a BMI under 32 generally have better outcomes. Higher BMI can increase stress on the implant and may affect long-term durability.

Conservative Care Has Failed You've tried non-surgical options—physical therapy, weight management, activity modification, injections (steroid, hyaluronic acid, platelet-rich plasma)—and they haven't provided adequate relief for at least 3-6 months.

How Partial Knee Replacement Works

The Procedure

Your partial knee replacement will likely be performed at Marina Outpatient Surgery Institute (MOSI) in Marina del Rey, a state-of-the-art surgery center designed for orthopedic procedures.

Standard Arthroscopic-Assisted Approach:

1. General anesthesia is administered
2. The surgeon makes a small incision (3-4 inches) over the affected compartment
3. Through this minimal-access approach, damaged bone and cartilage are carefully removed
4. Bone surfaces are precisely prepared
5. The implant components are positioned and secured
6. The incision is closed with sutures

Mako Robotic-Assisted Option: Many patients at Commons Clinic benefit from Mako robotic technology, an advanced system that provides enhanced precision during partial knee replacement. Here's how it works:

• Pre-operative CT scanning creates a 3D model of your unique knee anatomy
• Real-time guidance during surgery helps the surgeon position the implant with robotic precision—to within fractions of a millimeter
• Optimized implant placement based on your specific anatomy, rather than relying on generic surgical techniques
• Bone preservation is maximized because the surgeon removes only the necessary damaged bone

Dr. Wassef explains: "With Mako guidance, we can position the implant in the exact location that will provide the best long-term outcome for each patient's unique anatomy. This precision translates to better pain relief, improved function, and potentially longer implant longevity."

Outpatient Procedure

Unlike total knee replacement, which often requires hospitalization, most partial knee replacements at MOSI are performed on an outpatient basis. You'll arrive in the morning and return home the same day, with a family member or friend driving you.

Recovery Timeline: Back to Your Life Faster

One of the biggest advantages of partial knee replacement is the accelerated recovery compared to total knee replacement.

Week 1

• Day of surgery: You'll be able to walk with crutches same-day under physical therapy guidance
• Days 2-7: Continue crutches as needed, begin range-of-motion exercises at home, ice and elevate to manage swelling, pain managed with prescribed medications
• Follow-up visit: See Dr. Wassef to check incision healing and assess progress

Weeks 2-4

• Walking: Progress to walking without crutches by week 2-3
• Desk work: Most patients can return to desk-based work by week 2-4 (depending on pain and swelling)
• Physical therapy: Continue at-home exercises or outpatient physical therapy 2-3 times weekly
• Range of motion: Gradually increasing, typically 90-110 degrees by week 4

Weeks 6-8

• Activity level: Can perform most daily activities, including light walking, swimming, golf
• Work: Most patients with non-physical jobs have returned to full work duties
• Driving: Usually safe to drive again (assuming adequate pain control and no narcotic use)
• Exercise: Can progress to stationary cycling, elliptical machines

3 Months and Beyond

• Full activity: Most patients achieve full range of motion and pain-free function
• Impact activities: Can typically resume moderate hiking, tennis, recreational sports
• High-impact: Usually not recommended for running or jumping activities (these can accelerate implant wear)

Comparison to Total Knee Replacement Recovery: Total knee patients typically need 12+ weeks before returning to most activities and often 6+ months before feeling "normal." Partial knee patients often feel substantially better by 6-8 weeks, representing a significant quality-of-life advantage.

Partial vs. Total Knee Replacement: Side-by-Side Comparison

The Benefits and Risks: What You Should Know

Key Benefits

More Natural Knee Function Because you're preserving your natural knee anatomy—including your ligaments and the healthy compartments—your knee often feels more natural during everyday activities. Walking, climbing stairs, and kneeling feel closer to your pre-arthritis experience.

Faster Recovery Return to work, driving, and activities significantly faster than total knee replacement. Many patients feel back to normal within 2-3 months rather than 6+ months.

Smaller Incision Less surgical trauma means less pain, less swelling, less blood loss, and easier post-operative management.

Preserves Bone Stock If you ever need revision surgery in the future, the preserved bone in your knee provides more material to work with. This is particularly valuable if you're younger and might need a revision 15-20 years down the road.

Better Range of Motion Many partial knee patients achieve greater range of motion than total knee patients, with more natural-feeling movement, particularly bending the knee.

Fewer Restrictions While high-impact activities like running aren't recommended, moderate activities like golf, hiking, swimming, and tennis are generally possible after full recovery.

Important Risks and Considerations

Progression to Other Compartments The most significant long-term risk: arthritis may eventually develop in one of the preserved compartments. Studies show that 10-15% of partial knee patients will eventually need conversion to total knee replacement, usually within 10-15 years. This is still a minority of patients, and many enjoy a full lifetime with their partial knee replacement.

Implant Wear The bearing surfaces between the implant and your natural bone can wear over time, particularly with high-impact activities. This is why patient compliance with activity recommendations is important.

Conversion Surgery If arthritis progresses to another compartment and you need a total knee replacement later, the conversion surgery is more complex than a primary total knee replacement. The previous partial knee implant must be removed, and revisions have slightly higher complication rates than primary surgeries.

Early Revision While uncommon (2-5%), some patients require early revision within the first few years due to loosening, infection, or unexpected progression of arthritis in adjacent compartments.

Length of Benefit Period A partial knee replacement might "buy you" 10-15 pain-free years, whereas a total knee replacement might last 15-20+ years. For younger patients, this means potentially facing revision surgery earlier in life.

Why Patients Choose Commons Clinic for Partial Knee Replacement

Dr. Andrew Wassef, MD — Your Surgeon

Dr. Wassef is an orthopedic surgeon with specialized training and extensive experience in joint replacement, including partial knee replacement with robotic guidance. His approach emphasizes patient education, conservative decision-making, and surgical precision. Patients consistently report feeling heard and well-informed throughout their treatment journey.

Advanced Technology: Mako Robotic Assistance

Commons Clinic offers Mako robotic-assisted partial knee replacement, providing sub-millimeter precision in implant positioning. This technology allows Dr. Wassef to customize the procedure to your unique anatomy for optimal outcomes.

Marina Outpatient Surgery Institute (MOSI)

Located in Marina del Rey, MOSI is a state-of-the-art, surgery-center focused specifically on orthopedic procedures. The facility's specialized design, experienced surgical team, and high-volume orthopedic focus mean safer procedures and faster recovery. Same-day discharge (when medically appropriate) gets you back home quickly.

Extended Consultation Time

Unlike typical orthopedic practices, Commons Clinic allocates 3x the standard consultation time. This means your first appointment isn't rushed. You have time to ask questions, discuss your concerns, review imaging together, and fully understand your options.

Vertically Integrated Care

Everything happens under one roof:

• Orthopedic evaluation with Dr. Wassef
• Advanced imaging (X-ray, MRI, CT) available in-office
• Pre-operative medical clearance from on-site physicians
• Physical therapy provided by Commons Clinic therapists
• Post-operative care with consistent follow-up

No referrals between different clinics. No losing your medical records. Seamless, coordinated care.

Care Guarantee + Extended Warranty

Commons Clinic stands behind their work. Your partial knee replacement includes a 2-year Care Guarantee:

• Covered follow-up visits during the first 2 years
• Coverage for any implant-related issues during this period
• Direct access to Dr. Wassef's team if concerns arise

Virtual Consultations Nationwide

If you're unable to travel to Los Angeles for your initial consultation, Commons Clinic offers comprehensive virtual consultations. Discuss your case with Dr. Wassef via video, review your imaging together, and make an informed decision about proceeding with in-person evaluation.

Multiple Convenient Locations

Commons Clinic operates surgical/consultation spaces in:

• Santa Monica
• Marina del Rey (MOSI surgery center)
• Beverly Hills
• Long Beach

Choose the location most convenient to you.

Frequently Asked Questions

Will my insurance cover partial knee replacement?

Most major insurance plans cover partial knee replacement when medically necessary. Commons Clinic works with:

• Aetna
• Cigna
• Anthem Blue Cross
• Blue Shield of California
• United Healthcare
• Carrum Health
• Transcarent
• LanternCare

We also handle private pay and cash cases. During your consultation, we'll verify your specific coverage, discuss any out-of-pocket costs, and set clear financial expectations before proceeding.

How long does the partial knee replacement implant last?

Current data shows 85-95% of partial knee implants are still functioning well at 10 years. Beyond 10 years, longevity depends on your activity level, body weight, implant quality, and surgical technique. Many patients enjoy 15+ years of good function, though some may require revision earlier if arthritis progresses to other compartments.

Will I need physical therapy after surgery?

Yes, physical therapy is crucial for optimal recovery. Most patients benefit from 4-8 weeks of physical therapy, either in-clinic at Commons Clinic or with a therapist near their home. Dr. Wassef will provide specific recommendations based on your progress.

Can I return to sports after partial knee replacement?

Low-impact activities (golf, swimming, hiking, recreational tennis, bowling) are generally safe after full recovery (3+ months). High-impact activities (running, basketball, jumping sports) are typically not recommended because they can accelerate implant wear. Dr. Wassef will discuss what's appropriate for your specific situation.

What if arthritis develops in another compartment later?

This is possible—it's one of the risks of partial knee replacement. If arthritis progresses to involve another compartment and causes pain despite non-surgical treatment, conversion to total knee replacement may be necessary. This is more complex than a primary total knee replacement, but skilled surgeons perform it regularly with good results.

Am I a candidate if I had previous knee surgery?

Previous knee arthroscopy, ligament repair, or meniscal surgery doesn't automatically exclude you from partial knee replacement. However, it requires careful evaluation. The most important factor is that your ACL must be intact and functional. During your consultation, Dr. Wassef will review your surgical history and imaging to determine candidacy.

How much pain will I have after surgery?

Most patients manage post-operative pain with prescribed medications during the first 2 weeks, with significant improvement by week 3-4. Pain management is individualized—some patients need stronger medications briefly, others manage well with over-the-counter options. We focus on multimodal pain control (combining ice, elevation, medication, and early movement) to minimize opioid use.

Can I have the procedure on both knees if both are affected?

If both knees have single-compartment arthritis, staged bilateral partial knee replacement is possible. Typically, we perform one knee first, allow full recovery (3+ months), and then schedule the second knee. This approach allows you to maintain mobility during recovery and avoid being dependent on others for extended periods.

Key Takeaways

• Partial knee replacement is an excellent option for patients with single-compartment knee arthritis, an intact ACL, and failed conservative care.

• The procedure preserves your natural knee anatomy, resulting in a more natural-feeling knee with better long-term range of motion compared to total knee replacement.

• Recovery is significantly faster than total knee replacement—most patients return to work and activities within 6-8 weeks rather than 12+ weeks.

• Robotic guidance with Mako technology provides precision positioning of the implant, potentially improving long-term outcomes.

• The risks are manageable and worth considering against the substantial benefits of faster recovery and preservation of natural knee anatomy.

• Commons Clinic offers world-class care with extended consultation time, advanced technology, vertically integrated services, and a commitment to your long-term success.

Ready to Explore Your Options?

Don't accept limitations on your life without fully understanding all your options. Partial knee replacement might be the path that gets you back to the activities you love, with less downtime and a more natural-feeling knee.

Contact Commons Clinic today:

• Phone: (310) 437-7921
• Email: hello@commonsclinic.com
• Locations: Santa Monica | Marina del Rey | Beverly Hills | Long Beach
• Virtual consultations available nationwide

Schedule your comprehensive consultation with Dr. Andrew Wassef. In a relaxed, unhurried environment, we'll review your imaging, discuss your concerns, and determine whether partial knee replacement is right for you.

Your journey back to pain-free movement starts here.

Sources

American Academy of Orthopaedic Surgeons (AAOS). Partial Knee Replacement. OrthoInfo. https://orthoinfo.aaos.org

Kozinn, S. B., & Scott, R. D. (1989). Unicompartmental knee arthroplasty. The Journal of Bone and Joint Surgery, 71(1), 145-150.

Lustig, S., Magnussen, R. A., Cheze, L., & Neyret, P. (2012). Malalignment and functional impairment strongly correlate with quality of life after medial unicompartmental arthroplasty. Clinical Orthopaedics and Related Research, 470(11), 2971-2981.

Pandit, H., Jenkins, C., Gill, H. S., et al. (2015). Unnecessary contraindications for mobile-bearing unicompartmental arthroplasty in patients with interlocking varus deformity. The Journal of Bone and Joint Surgery, 90(12), 1581-1586.

Saldanha, K. A., Ghai, S., Moran, M., et al. (2007). The role of varus/valgus alignment in unicompartmental knee replacement. The Knee, 14(2), 142-148.

Word count: 2,847 | Published March 2026 | Updated Quarterly