When a patient is told they need knee replacement surgery, the immediate image that forms is of the entire knee joint being replaced. A large operation. A long recovery. A significant commitment.
For many patients, this picture is accurate. But for a meaningful subset of people with knee arthritis, there is an alternative that achieves the same outcome of pain relief and restored function through a smaller, more targeted operation with a faster recovery and a more natural-feeling result.
This is partial knee replacement, and understanding what it is, who qualifies for it, what the latest clinical evidence says about its outcomes, and how it compares to total knee replacement gives patients the knowledge they need to have a genuinely informed conversation with their orthopaedic surgeon.
What Is Partial Knee Replacement?
Partial knee replacement, also called unicompartmental knee arthroplasty (UKA), is a surgical procedure that replaces only the damaged portion of the knee joint rather than the entire joint surface.
The knee joint has three compartments:
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Medial compartment: The inner side of the knee, between the inner femur (thigh bone) and inner tibia (shin bone). This is the compartment most commonly affected by osteoarthritis and the most common site for partial knee replacement.
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Lateral compartment: The outer side of the knee. Less commonly affected in isolation.
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Patellofemoral compartment: The joint between the kneecap (patella) and the groove on the front of the femur.
When arthritis is confined to a single compartment, that compartment alone is resurfaced with metal and plastic implant components. The healthy bone, cartilage, and ligaments in the other compartments are left entirely untouched. Both cruciate ligaments (the ACL and PCL), which are removed in total knee replacement, are preserved in partial knee replacement.
Partial knee replacement addresses arthritis confined to one area of the knee. Rather than replacing the entire joint, the surgeon resurfaces only the damaged compartment while preserving healthy bone, cartilage, and ligaments.
This preservation of native tissue is the fundamental reason partial knee replacement patients describe their operated knee as feeling more natural than total replacement patients: the intact compartments and cruciate ligaments maintain much of the knee's normal proprioception and movement mechanics.
The Latest Evidence: What Does 2025 Research Tell Us?
The evidence base for partial knee replacement was significantly strengthened by a landmark clinical trial published in November 2025 in The Lancet Rheumatology.
A 2025 study found that for people with advanced knee osteoarthritis in which the damage is limited to one side of the joint, partial knee replacement is as effective as total knee replacement for pain relief and improved function and carries a similar need for additional surgeries within 10 years.
The trial included 528 people with arthritis only on the inside (medial side) of the knee joint who were randomly assigned to receive either total or partial knee replacement. This is one of the most robust head-to-head comparisons of the two procedures ever conducted, and its findings directly support expanding the appropriate use of partial knee replacement in correctly selected patients.
Additionally, a 2025 OrthoIndy update highlighted that robotic-assisted partial knee replacement is increasingly available at specialist orthopaedic centres, with technology providing real-time imaging and data to guide precise implant placement tailored to each patient's anatomy. The precision advantages of robotic assistance are particularly significant for partial knee replacement, where accurate alignment within a single compartment is more technically demanding than total replacement.
Who Is a Candidate for Partial Knee Replacement?
Patient selection is the most critical factor determining the success of partial knee replacement. Only 25 to 30% of patients who require knee replacement are anatomically and clinically eligible for the partial procedure. An experienced orthopaedic surgeon evaluates multiple criteria before recommending partial over total replacement.
Clinical Criteria That Support Partial Knee Replacement
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Single-compartment arthritis confirmed on imaging: The damage must be confined to one compartment on X-ray and MRI. Arthritis affecting two or three compartments significantly increases the likelihood of symptoms from the remaining compartments after partial replacement, and total replacement becomes the more appropriate choice.
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Intact anterior cruciate ligament (ACL): The ACL must be intact and functional. Partial knee replacement relies on the ACL for joint stability. If the ACL is absent, torn, or functionally deficient, the mechanical basis for a stable unicompartmental implant is absent.
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Intact articular cartilage in the remaining compartments: If significant cartilage loss is present in the non-replaced compartments, those compartments will become symptomatic after surgery regardless of how well the replaced compartment is functioning.
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Flexion deformity of less than 10 degrees: A fixed flexion deformity greater than 10 degrees is generally considered a relative contraindication for partial replacement.
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Adequate range of motion: A minimum pre-operative flexion of 90 degrees is generally required.
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Body weight considerations: Very high body weight increases the mechanical load on the partial implant. While obesity is not an absolute contraindication, it is a factor in the risk-benefit assessment.
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Age and activity level: Partial knee replacement is well-suited to both younger active patients who want to preserve as much native tissue as possible, and older patients where a smaller operation carries lower surgical risk. It is not exclusively for older patients as is sometimes assumed.
Clinical Features That Suggest the Patient Is NOT a Good Candidate
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Arthritis affecting multiple compartments
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Inflammatory arthritis (rheumatoid arthritis, psoriatic arthritis) causing generalised synovial disease
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Absent or deficient ACL
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Significant pre-operative varus or valgus deformity beyond 10 to 15 degrees
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A history of previous significant ligament injury or instability affecting the knee
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Active knee sepsis or prior deep knee infection
How Partial Knee Replacement Differs From Total Knee Replacement
Understanding the comparison between the two procedures helps patients appreciate both what partial replacement offers and what it does not.
What Partial Knee Replacement Offers That Total Does Not
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Preservation of healthy tissue: Bone, cartilage, and both cruciate ligaments in the non-replaced compartments remain intact. The surgical principle of preserving what is healthy avoids the permanent commitment of removing structures that are functioning normally.
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More natural feel: Patients who receive partial knee replacement consistently report a more natural-feeling knee than total replacement recipients in comparative studies. The preserved cruciate ligaments maintain proprioception and the normal arc of knee motion much more closely than total replacement, where both ligaments are removed.
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Faster recovery: The procedure is smaller, involves less blood loss, and causes less trauma to the surrounding soft tissues. Many patients go home on the day of surgery. Return to light activities typically occurs within two to three weeks, and return to full activity by six to eight weeks. Total knee replacement typically requires a hospital stay of two to three days and return to full activity over three to four months.
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Lower risk of some complications: Partial knee replacement carries lower rates of blood transfusion, thromboembolic events, and wound complications compared to total replacement in most comparative studies.
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Convertible: If the remaining compartments develop significant arthritis in future years, partial replacement can be converted to total knee replacement. The conversion surgery is more complex than a primary total replacement but is a well-established and reproducible procedure.
What Total Knee Replacement Offers That Partial Does Not
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Addresses all three compartments simultaneously: Total replacement eliminates the risk of future arthritis progression in the non-replaced compartments producing new symptoms.
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Broader eligibility: Patients who are not anatomically suitable for partial replacement, those with multi-compartment disease, inflammatory arthritis, or ACL deficiency, can be treated with total replacement.
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Longer established evidence base: Total knee replacement has decades of long-term outcome data. Partial replacement data, while increasingly robust, has a shorter follow-up history for implant survivorship at 15 to 20 years.
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Predictably corrects significant deformity: Varus or valgus deformity beyond the range suitable for partial replacement is reliably corrected by total knee replacement.
Signs That You May Be a Candidate for Partial Knee Replacement
A patient may be a candidate for partial knee replacement if their clinical and imaging picture includes:
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Knee pain that is clearly localised to one side of the knee: the inner side (most common) or the outer side, rather than generalised across the whole joint
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Pain on going up or downstairs, on prolonged walking, or after sitting, rather than constant severe pain at rest
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X-ray changes showing joint space narrowing and arthritis on one side of the joint only, with preserved joint space and normal bone on the other side
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An intact ACL confirmed on clinical examination or MRI
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Conservative management including physiotherapy, analgesics, intra-articular injections, and activity modification that has provided inadequate relief for a reasonable period
Pain that is genuinely and consistently localised to the medial (inner) knee with preserved lateral and patellofemoral compartments on imaging is the most classical and straightforward presentation for partial knee replacement assessment.
What the Surgery Involves
Partial knee replacement is performed under general or spinal anaesthesia. The procedure typically takes 60 to 90 minutes.
The surgeon makes an incision over the affected compartment of the knee, typically smaller than the incision used for total knee replacement. The damaged bone and cartilage in the affected compartment are removed with precision, leaving the cruciate ligaments and the other compartments entirely undisturbed. Metal components are fixed to the resurfaced bone ends of the femur and tibia, and a plastic spacer is inserted between them to create the new joint surface.
The wound is closed and the patient is moved to recovery. Most partial knee replacement patients are able to begin weight-bearing with the assistance of a frame on the day of surgery, a significantly faster start to rehabilitation than total replacement.
Many centres now perform partial knee replacement as a day procedure, with the patient going home on the day of surgery when appropriate criteria for safe discharge are met.
Recovery After Partial Knee Replacement
The faster recovery of partial knee replacement compared to total replacement is one of its most practically significant advantages for many patients.
Typical partial knee replacement recovery timeline:
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Day 0 to 1: Weight-bearing with frame or crutches begins on the day of surgery in most patients. Hospital discharge day 0 or day 1 for most cases.
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Weeks 1 to 2: Walking with reduced crutch or frame support. Pain management with oral analgesics. Wound check at one to two weeks.
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Weeks 2 to 4: Most patients walking with minimal or no support. Return to driving (in an automatic vehicle on the non-operated side) discussed with the surgeon at two to four weeks.
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Weeks 4 to 8: Return to light work, light exercise including walking and cycling. Physiotherapy exercises to restore range of motion and build quadriceps strength.
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Weeks 8 to 12: Return to full normal activities for most patients. Return to low-impact sport.
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Months 3 to 6: Progressive return to higher-impact and more demanding activities depending on individual recovery.
Post-operative physiotherapy is essential for optimising the outcome of partial knee replacement. Quadriceps strengthening, balance training, and graduated return to activity are the core rehabilitation priorities.
Dr. Omer Sheriff: Partial Knee Replacement at Humayun Hospital, T Nagar
For patients in T Nagar and across Chennai who are living with knee arthritis and want to understand whether partial knee replacement may be an appropriate option for them, Dr. Omer Sheriff at Humayun Hospital provides the specialist assessment and surgical expertise that this decision requires.
Dr. Omer Sheriff is a Consultant Orthopaedic and Joint Replacement Surgeon at Humayun Hospital, T Nagar, Chennai. He holds an MBBS, Diploma in Orthopaedics (Sri Ramachandra University), MS in Orthopaedics, and a Fellowship in Joint Replacement. He trained at CMC Vellore and brings international clinical experience from Hamad Medical Corporation, Doha, Qatar, to his practice in Chennai.
With over 25 years of experience and more than 3,500 successful orthopaedic procedures, Dr. Omer Sheriff brings both the technical surgical expertise required for partial knee replacement and the patient assessment experience needed to accurately identify which patients will be best served by the partial approach versus total replacement.
He is a life member of the Indian Orthopaedic Association (IOA), the Indian Society of Hip and Knee Surgeons (ISHKS), and the Tamil Nadu Orthopaedic Association (TNOA).
We offer:
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Clinical examination and knee assessment including range of motion, ligament stability, and compartment-specific pain mapping
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Weight-bearing X-rays and MRI for compartment damage assessment and ACL status
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Honest, individualised surgical recommendation: partial replacement when the anatomy and clinical picture support it, total replacement when multi-compartment disease or other factors indicate it
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Surgical expertise in both unicompartmental knee arthroplasty and total knee arthroplasty
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Structured post-operative physiotherapy coordination
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Clear, realistic recovery timeline guidance based on each patient's individual circumstances
If you have been told you need a knee replacement and want to understand whether the partial procedure may be appropriate for you, a consultation with Dr. Omer Sheriff starts that conversation with the clinical specificity it deserves.
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