What is Total Knee Replacement?
Total knee replacement (TKR) — also known as total knee arthroplasty — is a surgical procedure in which the damaged surfaces of the knee joint are removed and replaced with precisely engineered metal and plastic components, restoring a smooth, pain-free articulating surface. It is the most commonly performed major joint replacement in the UK.
The knee has three distinct compartments: the medial (inner), lateral (outer), and patellofemoral (kneecap). In a total knee replacement, all three surfaces are resurfaced. The result is a reconstructed joint that moves naturally, is stable in all positions, and — crucially — is free of the deep arthritic pain that brought the patient to surgery.
Approximately 110,000 knee replacements are performed in the UK each year. The National Joint Registry (NJR) holds outcome data from well over two million procedures, making it one of the most thoroughly monitored surgical interventions in medicine. Mr. Lodge performs total knee replacement at York Teaching Hospital (NHS) and at Nuffield Health York Hospital and Ramsay Clifton Park Hospital (private), serving patients from across North Yorkshire, West Yorkshire and East Yorkshire. He is a registered NJR surgeon; patient-reported outcome measures (PROMs) are collected routinely from all his patients to ensure outcomes are continuously audited and evidence-based.
Knee replacement is offered when conservative measures — including physiotherapy, weight management, medication and injections — have been genuinely tried and found insufficient. The decision to operate is always made jointly, following a thorough review of symptoms, examination findings, X-ray appearances, overall health, and the patient's individual expectations and goals.
An important distinction from hip replacement: Patients sometimes expect a similar experience to a hip replacement that a friend or relative has had. Knee replacement recovery differs — it typically requires more committed rehabilitation, and regaining range of movement demands considerable effort from the patient in the early weeks. With that commitment, the results can be equally life-changing.
How the Operation Works
Total knee replacement involves the careful removal of the damaged articular surfaces of the femur (thigh bone), tibia (shin bone), and in most cases the undersurface of the patella (kneecap), replacing them with metal and plastic components that recreate smooth, aligned and pain-free movement.
The operation is performed under spinal or general anaesthesia, typically taking 90 minutes to two hours. An incision is made along the front of the knee, and precision cutting guides — aligned to the patient's anatomy — are used to remove the arthritic bone and cartilage. The components are then trialled, adjusted and finally implanted.
A critical element of the procedure is soft tissue balancing — ensuring that the collateral ligaments on both sides of the joint are equally tensioned throughout the full arc of movement. A well-balanced knee replacement moves naturally, is stable in all positions, and places even load on the polyethylene bearing surface. Poor balancing remains one of the most common causes of a suboptimal outcome, and meticulous attention to this step is central to Mr. Lodge's operative technique.
All decisions — from implant choice to fixation method to whether to resurface the patella — are tailored to each patient's anatomy, age, bone quality and clinical circumstances, and are discussed in advance so that the operative plan is fully understood before surgery.
Femoral Component
A curved cobalt-chrome metal shell that resurfaces the end of the femur, recreating the smooth, rounded contour of the original femoral condyles. Polished to a mirror finish to minimise bearing wear.
Tibial Tray
A flat metal platform fixed to the top of the tibia, providing a stable base for the polyethylene insert. Carefully sized and positioned to restore the correct alignment and joint line height.
Polyethylene Insert
A highly cross-linked polyethylene bearing seated on the tibial tray. This is the articulating surface of the new joint — the functional equivalent of the cartilage — engineered for exceptional durability and low wear.
Patellar Button
A dome-shaped polyethylene component that resurfaces the back of the kneecap, allowing it to glide smoothly over the femoral component. Resurfaced routinely by Mr. Lodge to optimise anterior knee comfort and function.
The Role of the Ligaments
Unlike hip replacement, where the natural ligaments are largely removed during the procedure, knee replacement relies on the patient's own collateral ligaments for stability. The medial and lateral collateral ligaments are preserved and balanced intraoperatively. The posterior cruciate ligament (PCL) may be retained or sacrificed depending on the implant design selected — both approaches have excellent outcomes when used appropriately. The anterior cruciate ligament (ACL) is routinely removed as part of the procedure.
Choosing the Right Type of Knee Replacement
Not every patient with knee arthritis requires a total knee replacement. In selected cases where arthritis is confined to a single compartment of the knee, a partial replacement may be considered. The right choice depends on a thorough assessment of which compartments are affected, the integrity of the ligaments, the degree of deformity, and the overall clinical picture.
Total Knee Replacement
Resurfaces all three compartments of the knee. The most commonly performed type and appropriate when arthritis is widespread, or when significant deformity is present. Well-evidenced with outstanding registry data at 10 and 15 years.
Standard — most patientsPartial (Unicompartmental)
Replaces only the damaged medial or lateral compartment, preserving intact bone, cartilage and ligaments. Recovery is faster and the knee can feel more natural — but patient selection is critical. Not suitable for all.
Carefully selected patientsPatellofemoral Replacement
Addresses isolated arthritis between the kneecap and the front of the femur. Appropriate only when medial and lateral compartments are well preserved. Conversion to total replacement is straightforward if arthritis progresses.
Highly selected patientsPatient selection is everything. A well-selected partial knee replacement can produce an outstanding outcome with a faster recovery and more natural feel than a total replacement. However, care must be taken to ensure there is no degenerative changes in the remaining knee to minimise development of recurrent discomfort in the future. Mr Lodge does not offer partial joint replacements but does assess and refer appropriate candidates to his colleagues where indicated. Mr. Lodge will guide you on which type is appropriate based on your individual assessment.
How Are Implants Fixed to Bone?
As with hip replacement, knee implants can be secured using acrylic bone cement or through biological fixation, where bone grows directly onto the implant surface. The vast majority of knee replacements in the UK are performed with cemented fixation, and this remains Mr. Lodge's standard technique — supported by the strongest long-term evidence base of any fixation method in knee arthroplasty.
Cemented Fixation
Standard approach — the gold standard in knee replacement
- Acrylic bone cement is pressurised into the cut bone surfaces before the components are seated, providing immediate and highly reliable fixation
- Allows full weight-bearing from the day of surgery in most patients
- The most extensively evidenced fixation method in knee replacement, with decades of outcome data confirming excellent longevity
- Appropriate for the majority of patients across all ages, and particularly in those with softer or osteoporotic bone
- The dominant fixation method in the NJR, with cemented TKR demonstrating the lowest all-cause revision rates at long-term follow-up
Uncemented Fixation
Growing evidence in younger, more active patients
- Porous-coated implant surfaces allow bone to grow directly onto the component, achieving biological fixation over weeks to months
- Increasingly used in younger patients with excellent bone quality where very long-term implant survivorship is the priority
- May reduce the risk of aseptic cement-bone interface failure at very long follow-up — a potential advantage over cemented fixation
- Requires precise bone preparation to achieve immediate mechanical stability while biological integration develops
- NJR data now supports equivalent survivorship to cemented fixation in appropriately selected patients, with continued follow-up ongoing
What Results Can You Expect?
Total knee replacement is one of the most effective elective surgical procedures available, with the large majority of patients experiencing a significant and sustained improvement in pain and quality of life. However, it is important to approach surgery with realistic expectations — a knee replacement restores an excellent quality of life, but does not create an entirely normal knee.
Over 80% of patients report being satisfied or very satisfied with their outcome at one year following surgery. The primary benefit is a dramatic reduction in the deep, constant arthritic pain that drove the patient to seek treatment — pain that is frequently present from the earliest days of recovery. Function, range of movement and confidence with activity continue to improve over many months as the knee settles and muscles strengthen.
It is worth being open about the fact that the satisfaction rate following knee replacement is somewhat lower than for hip replacement, and this difference is well-evidenced. A small but significant proportion of patients — estimated at around 4–5% — continue to experience pain after a technically successful knee replacement without any identifiable mechanical cause. The reasons for this remain incompletely understood. Thorough pre-operative assessment, including careful evaluation of pain characteristics and psychological readiness, helps identify patients at higher risk of this outcome and informs an honest discussion of expectations before proceeding.
Implant Longevity & Long-Term Follow-up
Modern knee replacement implants, particularly those using highly cross-linked polyethylene bearings, are expected to function reliably for 15–20 years or more in the majority of patients. NJR data confirms implant survival rates of approximately 95% at ten years. Younger, more active patients may eventually require a revision procedure during their lifetime — a consideration that informs implant selection and the emphasis on bone preservation at primary surgery.
Long-term follow-up appointments are an important part of Mr. Lodge's practice. Regular clinical review and X-ray assessment allow early identification of any signs of wear or loosening, ensuring that any necessary intervention can be planned in a timely and controlled manner.
- Pain relief: The primary aim. Dramatic reduction in arthritic pain is typically experienced within the first few weeks — often the first thing patients notice.
- Recovery timeline: Most patients are walking independently within 6 weeks. Full settlement of the knee — including resolution of swelling and achieving maximum range of movement — typically takes 6–12 months.
- Range of movement: Most patients achieve 100–120° of flexion. Full flexion is not always restored. Kneeling may remain uncomfortable due to scar sensitivity and soft tissue changes.
- Activity: Low-impact activities — walking, cycling, swimming, golf — are actively encouraged. High-impact activities such as running are generally discouraged to reduce wear on the bearing surface.
- Hospital stay: Typically 1–3 nights, with discharge once the patient is independently mobile and medically fit to go home.
What Are the Risks?
Total knee replacement is a safe and well-established procedure, and the vast majority of patients undergo surgery without encountering any significant complications. That said, as with any major operation, it is important that you understand the potential risks before giving your consent to proceed. All of these will be covered in detail at your pre-operative consent appointment.
Infection
~0.5–1%Infection is the most serious potential complication following knee replacement. Prophylactic antibiotics, laminar flow theatre conditions, meticulous sterile technique and careful wound management are all used to minimise this risk. Superficial wound infections are uncommon and usually resolve with antibiotic treatment. Deep infection involving the implant itself — periprosthetic joint infection (PJI) — is more serious and may require further surgery, including in severe cases the temporary removal of the implant while infection is eradicated. Risk is higher in patients who are diabetic, overweight, immunosuppressed, or who have had previous knee surgery. Prompt treatment of infections elsewhere in the body throughout the lifetime of the replacement is important.
Blood Clots (DVT / Pulmonary Embolus)
Reduced with prophylaxisDeep vein thrombosis (DVT) and pulmonary embolus (PE) are recognised risks following any major lower limb surgery. To reduce this risk, Mr. Lodge uses spinal anaesthesia where possible, mobilises patients early, prescribes four weeks of low molecular weight heparin (LMWH) injections, and recommends thromboembolic deterrent (TED) compression stockings. Leg swelling, redness or warmth not settling with elevation overnight should be reported promptly.
Stiffness & Restricted Range of Movement
Minimised by early physiotherapyAchieving and maintaining good knee flexion is one of the greatest challenges of knee replacement recovery. In a small number of patients, excessive scar tissue forms within the joint — a complication known as arthrofibrosis — preventing adequate range of movement despite good physiotherapy effort. Where this occurs, a manipulation under anaesthetic (MUA) may be performed, whereby the knee is gently but firmly bent under a short general anaesthetic to break down scar adhesions. MUA is most effective when carried out early — within the first three months of surgery, before scar tissue matures. Committed engagement with physiotherapy in the first six weeks is the single most effective preventive measure.
Nerve & Vessel Injury
RareThe common peroneal nerve — which passes around the outside of the knee — is at risk during knee replacement, particularly in cases requiring correction of significant valgus (knock-knee) deformity. Injury can cause weakness in lifting the foot (foot drop) and numbness over the dorsum of the foot. The majority of cases are temporary and resolve over weeks to months; permanent injury is rare. Significant vascular injury is also very rare but is a recognised risk in complex revision or deformity-correction cases.
Loosening, Wear & Long-term Failure
Long-term considerationOver time, even a well-functioning knee replacement is subject to wear of the polyethylene bearing surface and, eventually, potential loosening of the implant-bone interface. Modern highly cross-linked polyethylene has dramatically reduced wear-related failure. Aseptic loosening — where the fixation between implant and bone fails in the absence of infection — is the most common cause of revision surgery at long-term follow-up. Regular review appointments with X-ray assessment allow early detection of any signs of loosening before significant bone loss develops, preserving options for future reconstruction.
Persistent Pain Without Identifiable Cause
~4–5% of patientsA small but significant proportion of patients — estimated at around 4–5% — continue to experience pain after a technically successful knee replacement, without any identifiable mechanical cause such as infection, loosening or malalignment. This phenomenon is one of the most challenging issues in knee arthroplasty and remains incompletely understood. Pre-operative assessment of pain characteristics, patient expectations and psychological factors helps identify those at higher risk, and informs a frank and honest discussion before surgery is recommended.
Overall perspective: The chance of undergoing a straightforward primary knee replacement without a major complication is approximately 98–99%. The risks above are real but uncommon, and should be considered in the context of the very high probability of a good outcome. The aim of this information is not to alarm, but to ensure every patient can give genuinely informed consent before proceeding.
Is Knee Replacement Right for You?
The decision to proceed with total knee replacement is never taken in isolation. It is always made together — following a thorough discussion of your symptoms, examination findings, X-ray appearances, overall health, expectations and personal goals.
There is no fixed threshold at which knee replacement becomes the right answer. Surgery is most appropriate when your symptoms are having a significant and sustained impact on your quality of life; when conservative measures have been genuinely tried and found insufficient; when the X-ray shows arthritis consistent with your symptoms; and when you are in the best possible health to commit to surgery and the rehabilitation that follows.
If you are considering knee replacement and would like a specialist assessment, contact us to arrange a consultation with Mr. Lodge. He will take the time to understand your individual situation and give you an honest, evidence-based opinion on your options — including whether the time is right for surgery now, or whether further conservative measures are worth pursuing first.