Knee Surgery

Partial Knee Replacement

Partial knee replacement (unicompartmental knee arthroplasty) targets only the damaged area of the knee joint. By preserving healthy cartilage and ligaments such as the ACL and PCL, patients experience a natural movement knee joint with smaller incisions.

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On This Page

Recovery

Minimal tissue disturbance, outpatient surgery eligibility, swift recovery.

Clinical Focus

Medial, lateral, or patellofemoral compartment resurfacing; ACL/PCL ligament preservation.

Ideal Candidate

Patients with localized knee arthritis restricted to a single compartment.

Understanding Your Procedure

In-Depth: Partial Knee Replacement

A clear, comprehensive look at what this procedure is, how it works, and why it may be the right choice for you.

The knee joint has three compartments: medial (inner), lateral (outer), and patellofemoral (). In many patients, only affects one of these compartments, while the other two remain healthy. ( knee ) resurfaces only the damaged compartment, leaving the healthy compartments and crucial ligaments—particularly the ACL and PCL—completely intact.Because the ACL and PCL are preserved, the knee continues to function with its natural kinematics. Patients often report that a feels more like their natural knee than a —they can often kneel, squat, and return to activities that total knee patients find difficult. The incision is smaller, recovery is faster, and blood loss is less. is performed with the MAKO robotic system, which allows Dr. Sobh to plan the exact bone cuts from a and execute them with sub-millimeter precision. This is especially important in , where accurate is critical to long-term success. If arthritis eventually progresses to other compartments, a partial knee can be reliably converted to a .

Partial Knee Replacement anatomical illustration

Partial Knee Replacement — illustrated overview of the surgical approach and implant placement.

20-30+

Years Implant Lifespan

90%+

Patient Satisfaction

24h

Walking Post-Op

<1%

Complication Rate

What Makes This Approach Different

ACL & PCL Preservation

Unlike , preserves both cruciate ligaments, maintaining the knee's natural biomechanics and stability.

Smaller Incision

The incision is typically half the length of a total knee incision, resulting in less tissue trauma, less blood loss, and a smaller scar.

Faster Recovery

Most partial knee patients walk unassisted within 1-2 weeks and return to golf, tennis, and other activities in 6-10 weeks—roughly half the time of total knee recovery.

Convertible to Total Knee

If arthritis progresses in other compartments, a partial knee can be revised to a total knee. Because bone is preserved, this revision is typically simpler than revising a total knee.

Clinical information reviewed and edited by Dr. Ali H. Sobh, MD, board-certified orthopedic surgeon. Content synthesized from peer-reviewed orthopedic literature, American Academy of Orthopaedic Surgeons (AAOS) guidelines, and Dr. Sobh's fellowship training at Rush University Medical Center. Last updated 2025.

Interactive Education

See How Your Joint Works

Understanding your condition is the first step toward confident decisions. Use this interactive visualizer to explore the anatomy of the knee joint, compare a healthy joint with an arthritic one, and see exactly what partial knee replacement restores.

1
Toggle states to compare healthy, arthritic, and post-surgical joints.
2
Tap the dots to learn about each anatomical structure.
3
Watch the motion to see how the joint moves during activity.

Interactive Joint Visualizer

Explore how partial knee replacement works

For Education

Front View

100%

Tap the dots to explore the joint anatomy

Arthritic / Damaged

Illustration for educational purposes. Not a diagnostic image.

Recognizing the Signs

Common Symptoms

Many patients live with joint pain for years before seeking treatment. If you recognize several of these symptoms, it may be time to schedule a consultation.

When to seek care

If your symptoms interfere with sleep, work, or activities you enjoy, or if conservative treatments no longer provide relief, a surgical consultation is appropriate.

Pain concentrated on one side of the knee (inner or outer)

Stiffness and swelling limited to one area of the knee

Pain that worsens with prolonged activity but eases with rest

A feeling of catching or locking in one part of the knee

Knee bends relatively well—full range of motion is still present

Discomfort that has not progressed to the entire knee joint

Dr. Ali H. Sobh, MD

Board Certified & Fellowship-Trained Orthopedic Surgeon

Rush University Medical Center Fellowship

Hour Detroit Top Doc Award 2025

900+ 5-Star Google Reviews

Why Dr. Sobh for This Procedure

Fellowship-Trained Expertise in Partial Knee Replacement

Dr. Sobh combines his MAKO robotic training with partial knee expertise to precisely resurface only the damaged compartment. Because he uses robotic guidance, the bone cuts are extremely accurate and conservative—preserving healthy bone and your crucial ACL and PCL ligaments. His fellowship training emphasized patient selection: he carefully evaluates imaging to confirm arthritis is truly confined to one compartment, ensuring partial replacement will deliver long-lasting relief rather than masking progression in other areas.

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Conditions Treated

Is Partial Knee Replacement Right for You?

Dr. Sobh may recommend this procedure for patients diagnosed with the following conditions.

Medial compartment knee arthritisLateral compartment knee arthritisPatellofemoral arthritisAvascular necrosis in one knee compartmentIsolated cartilage damage

A thorough consultation and imaging review will confirm the best treatment path for your specific situation.

Are You a Candidate?

Candidacy for Partial Knee Replacement

Dr. Sobh carefully evaluates each patient to determine if this procedure is the right fit. Here's a general guide — your individual consultation will provide a definitive answer.

Good Candidate

Patients with arthritis confined to a single compartment (medial, lateral, or patellofemoral) confirmed on weight-bearing X-rays and MRI, with intact ACL and correctable deformity.

Good Candidate

Active patients who want to preserve their ACL and return to sports or kneeling activities that total knee replacement may limit.

May Not Be a Candidate

Patients with arthritis in two or more compartments, a deficient ACL, severe fixed deformity (>15°), or inflammatory arthritis (rheumatoid) are not candidates for partial knee replacement.

May Not Be a Candidate

Patients with morbid obesity (BMI >40) may have higher failure rates with partial knee replacement due to increased load on the implant.

Technology & Techniques

Advanced Technology Used in Your Surgery

Dr. Sobh uses these specialized tools and technologies to ensure the highest level of precision and safety during your procedure.

MAKO Robotic Planning

A CT scan creates a 3D model of your knee. Dr. Sobh plans the exact bone cuts for the damaged compartment only, preserving healthy bone and ligaments.

Unicompartmental Implant

A metal femoral component and metal tibial baseplate with a polyethylene insert replace only the damaged compartment's bearing surfaces.

Ligament-Balancing Assessment

The robotic system allows Dr. Sobh to assess ligament tension through the full range of motion, ensuring the partial implant moves naturally with your preserved ligaments.

How the Surgery Works

Understanding Your Surgical Journey

From your first consultation to full recovery, here's what to expect at each stage. Dr. Sobh and the team at Michigan Orthopaedic Surgeons will guide you through every step.

MAKO Robotic Planning

A creates a 3D model of your knee. Dr. Sobh plans the exact bone cuts and position for the damaged compartment only, preserving healthy bone and ligaments.

Targeted Resurfacing

Only the arthritic portion of the knee is resurfaced with a metal and plastic . Your ACL, PCL, and healthy cartilage in other compartments remain intact.

Outpatient Recovery

Because the procedure is less invasive than , many patients qualify for outpatient surgery and return home the same day.

Recovery Timeline

Your Path Back to Activity

Recovery timelines vary by individual and procedure complexity. Dr. Sobh will provide a personalized rehabilitation plan. Here's a general guide to what most patients experience.

0-24 hours

Day of Surgery

Walk with assistance. Many patients go home the same day. Begin gentle range-of-motion exercises.

1-2 weeks

Early Recovery

Walk with minimal support. Physical therapy focuses on knee bend and quadriceps activation. Less pain than total knee replacement.

2-6 weeks

Progressive Activity

Return to driving and work. Resume walking, stationary bike, and swimming. Therapy advances to strengthening.

6-10 weeks

Full Recovery

Return to golf, tennis, and recreational sports. The preserved ligaments provide a more natural-feeling knee than total replacement.

Comparing Your Options

Partial Knee Replacement vs. Alternatives

Understanding how partial knee replacement compares to other treatment options helps you make an informed decision. Dr. Sobh will discuss all viable options during your consultation.

Total Knee Replacement

Total knee replaces all three compartments and removes the ACL (and usually the PCL). It's necessary when arthritis affects multiple compartments but results in a less natural-feeling knee and longer recovery.

Knee Arthroscopy

Arthroscopy can clean up torn or cartilage flaps but cannot reverse arthritis. It may temporarily help but does not resurface the damaged joint surface like does.

High Tibial Osteotomy (HTO)

HTO realigns the leg by cutting and repositioning the to shift weight away from the arthritic compartment. It's an option for younger, active patients but has a longer recovery and doesn't resurface the damaged cartilage.

Patient Journey Tip

Partial knee replacement patients often say their knee feels 'like my own knee' rather than an artificial joint. This is because your ACL, PCL, and healthy compartments remain intact, preserving the knee's natural proprioception and movement patterns.

Benefits

This procedure offers significant advantages for qualified patients:

Preserves healthy bone, cartilage, and ligaments (ACL/PCL)
Smaller incision and less tissue damage
Faster recovery than total knee replacement
More natural knee bending and stability
Often performed as outpatient surgery
Easier to revise in the future if needed

Potential Risks

As with any surgery, there are potential risks. Dr. Sobh takes extensive measures to minimize them:

Progression of arthritis in other compartments
Implant loosening over time
Infection (rare)
Blood clots—prevented with medication and early walking
Persistent pain if arthritis progresses
Anesthesia-related risks

Important

This information is for educational purposes only. Your individual risks depend on your health history. Dr. Sobh will discuss your specific risk profile during your consultation.

Patient Questions

Frequently Asked Questions

Common questions patients ask about partial knee replacement.

Am I a candidate for partial knee replacement?

You are a good candidate if your arthritis is confined to one compartment of your knee and your ligaments (especially the ACL) are intact. Dr. Sobh will use X-rays and MRI to confirm this during your consultation.

How is partial knee replacement different from total knee replacement?

resurfaces only the damaged compartment, preserving healthy bone and ligaments. This results in a more natural-feeling knee, faster recovery, and smaller incision. resurfaces the entire joint.

Will I need a total knee replacement later?

Not necessarily. If arthritis progresses in the other compartments, a partial knee can be converted to a . Because partial replacement preserves bone, this conversion is typically straightforward.

How long does a partial knee implant last?

Partial knee implants can last 15-20 years or more, depending on activity level, weight, and positioning. Dr. Sobh's MAKO robotic precision helps maximize longevity.

Medically ReviewedLast reviewed: August 14, 2026

Dr. Ali H. Sobh, MD

Board Certified & Fellowship-Trained Orthopedic Surgeon — Minimally-Invasive Hip & Knee Replacement Specialist

This procedure page was clinically reviewed and approved by Dr. Ali H. Sobh, MD, a board-certified, fellowship-trained orthopedic surgeon specializing in direct anterior hip replacement and MAKO robotic knee surgery. Dr. Sobh graduated with high honors from Wayne State University School of Medicine and completed his adult reconstruction fellowship at Rush University Medical Center in Chicago. He practices at Michigan Orthopaedic Surgeons (MOS) with offices in Royal Oak and Southfield, Michigan.

View Full Credentials Editorial Standards

This information is for educational purposes only and is not a substitute for professional medical advice. Individual results and recovery timelines vary. Schedule a consultation with Dr. Sobh to discuss your specific condition and treatment options.

Happy, active patients enjoying life after orthopedic surgery recovery with Dr. Ali H. Sobh

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Ready to Take the Next Step?

Schedule a personalized consultation with Dr. Sobh to discuss whether partial knee replacement is right for you. Our team will help coordinate your visit, insurance verification, and pre-operative planning.

Book an Appointment Call (833) 667-3627