Partial Knee Replacement (PKR): A Complete Guide

Introduction to Partial Knee Replacement (PKR)

Partial Knee Replacement (PKR), also called unicompartmental knee replacement, is a minimally invasive surgical option for patients with arthritis or damage confined to one compartment of the knee. Unlike total knee replacement (TKR), PKR preserves healthy bone, ligaments, and cartilage, leading to a quicker recovery and more natural knee movement.

PKR is ideal for patients with localized osteoarthritis who haven’t responded to conservative treatments like physical therapy or injections. The procedure replaces only the damaged part of the knee with artificial components, reducing pain and restoring mobility. Studies show that PKR patients often experience less post-operative pain, shorter hospital stays, and faster rehabilitation compared to TKR.

If you’re considering PKR, this guide will help you understand the procedure, benefits, risks, and recovery process to make an informed decision.

Who is a Candidate for PKR? (Eligibility Criteria)

Not everyone with knee pain qualifies for PKR. Ideal candidates meet the following criteria:

Localized Arthritis: Damage should be limited to one knee compartment (medial, lateral, or patellofemoral).
Stable Ligaments: The knee’s ligaments (especially ACL) must be intact.
Healthy Weight: Obesity increases implant failure risk; BMI under 40 is preferred.
Moderate Pain: Severe deformities or widespread arthritis may require TKR instead.
Failed Non-Surgical Treatments: Physical therapy, medications, or injections didn’t provide relief.

Patients under 60 with active lifestyles often benefit most, but age alone isn’t a disqualifier. A thorough evaluation by an orthopedic surgeon, including imaging tests (X-rays/MRI), determines candidacy.

How PKR Differs from Total Knee Replacement (TKR)

While both procedures address knee arthritis, PKR and TKR have key differences:

Factor	PKR	TKR
Invasiveness	Minimally invasive (smaller incision)	More invasive (larger incision)
Bone Preservation	Preserves healthy bone & ligaments	Removes entire knee joint
Recovery Time	2–6 weeks	6–12 weeks
Longevity	10–15 years (may need revision)	15–20 years

PKR is a joint-preserving option, but if arthritis progresses, conversion to TKR may be needed later.

The PKR Procedure: Step-by-Step Overview

PKR typically follows these steps:

Pre-Op Preparation: Blood tests, imaging, and pre-surgical instructions (e.g., fasting).
Anesthesia: General or spinal anesthesia ensures no pain during surgery.
Incision: A 3–5 inch cut is made over the knee.
Damaged Tissue Removal: The surgeon removes only the diseased bone and cartilage.
Implant Placement: Metal and plastic components are secured to the femur and tibia.
Closure: Stitches or staples close the incision.

The surgery takes 1–2 hours, and most patients walk with assistance the same day. Hospital stays are usually 1–3 days, followed by outpatient physical therapy.

Benefits and Advantages of PKR

PKR offers several advantages over TKR:

Faster Recovery: Less tissue damage means quicker return to daily activities.
More Natural Feel: Retained ligaments improve knee stability and motion.
Lower Blood Loss: Reduced risk of transfusion compared to TKR.
Outpatient Potential: Some PKRs are done as outpatient procedures.
Reversible: Can be converted to TKR if needed later.

Studies report 90% patient satisfaction rates at 5 years post-PKR, with many resuming low-impact sports like golf or cycling.

Potential Risks and Complications

While PKR is generally safe, risks include:

Infection: Rare (<1%) but may require antibiotics or revision.
Blood Clots: Prevented with blood thinners and early movement.
Implant Loosening/Wear: More common in younger, active patients.
Persistent Pain: May occur if arthritis spreads to other compartments.
Nerve Damage: Temporary numbness near the incision.

Choosing an experienced surgeon and following post-op instructions minimizes these risks.

Recovery Timeline & Rehabilitation Tips

Typical PKR recovery milestones:

Week 1–2: Use a walker/cane; focus on reducing swelling and gentle motion.
Week 3–6: Gradually increase walking; outpatient PT begins.
Month 2–3: Resume driving and light activities.
Month 6+: Full recovery; low-impact exercises encouraged.

Rehab tips: Ice regularly, adhere to PT exercises, avoid high-impact sports (running, basketball), and attend follow-ups to monitor progress.

Frequently Asked Questions (FAQs) About PKR

Q: How long does a PKR implant last?

A: 10–15 years, though some last 20+ with proper care.

Q: Will I need a second surgery later?

A: If arthritis progresses, a TKR may eventually be needed.

Q: Can I kneel after PKR?

A: Yes, but it may feel uncomfortable initially.

Conclusion: Is PKR Right for You?

PKR is an excellent option for patients with localized knee arthritis who want a faster recovery and more natural knee function than TKR offers. However, long-term outcomes depend on proper patient selection, surgical skill, and rehabilitation.

If your pain is confined to one knee compartment and conservative treatments haven’t helped, consult an orthopedic surgeon to discuss whether PKR fits your needs.