Knee Replacement Risks and Complications

Knee replacement is a major operation that can provide substantial pain relief and improved function for appropriately selected patients, but it cannot be risk-free. Good consent should explain both the expected recovery experience and the less common complications that may require additional treatment, hospital care or revision surgery.

Risk is individual. Age, diabetes, heart or lung disease, kidney function, anaemia, obesity, smoking, previous blood clots, skin condition, circulation, previous knee surgery, bone quality, deformity, one- or two-knee surgery and revision complexity all influence the plan. A complication list should support shared decision-making rather than create fear or imply that every patient has the same probability.

Quick Answer: What Are the Main Risks?

Important risks include infection, blood clots, bleeding, wound problems, stiffness, persistent pain, instability, fracture, nerve or blood-vessel injury, implant wear or loosening, falls, anaesthetic or medical complications and the possibility of further surgery. Most patients do not experience a major complication, but no surgeon, implant, approach or robotic system can guarantee that complications will not occur.

Expected Recovery Versus a Complication

Pain, swelling, bruising, warmth, fatigue, disturbed sleep, temporary weakness, use of a walker and difficulty bending are expected during early recovery. Concern increases when symptoms progressively worsen, return after improvement, become severe at rest or occur with drainage, spreading redness, fever, calf pain, repeated buckling, a fall or inability to bear weight. The overall pattern matters more than one isolated symptom.

Infection Around the Implant

Infection may involve the skin and wound or extend deep around the replacement, where bacteria can attach to metal and polyethylene surfaces. It can occur soon after surgery or months or years later. Warning patterns include persistent drainage, increasing pain, redness, swelling, stiffness or decline in a previously well-functioning knee. Fever may be absent.

Deep infection can require surgical cleaning, component exchange, implant removal, staged reconstruction and prolonged antibiotics. Read Infection After Knee Replacement.

Deep-Vein Thrombosis and Pulmonary Embolism

Major lower-limb surgery and temporary reduced mobility increase venous-thromboembolism risk. A deep-vein thrombosis may cause new calf pain, tenderness, warmth or unequal swelling. A pulmonary embolism can cause sudden breathlessness, chest pain, coughing blood, rapid heartbeat, fainting or collapse and is an emergency.

Prevention may include early mobilisation, ankle movements, compression in selected patients and anticoagulant medicine matched to clot and bleeding risk. Read Blood Clots After Knee Replacement.

Bleeding, Bruising and Anaemia

Blood loss and bruising are expected to some degree. Tranexamic acid and modern surgical pathways can reduce blood loss, but some patients develop symptomatic anaemia, wound bleeding or a collection of blood called a haematoma. Risk is influenced by preoperative haemoglobin, anticoagulants, bleeding disorders, kidney disease and procedure complexity. Significant dizziness, fainting, rapid heartbeat, breathlessness or expanding swelling requires assessment.

Wound Healing Problems

The incision may heal slowly, separate, blister or continue draining. Diabetes, smoking, obesity, poor circulation, malnutrition, previous scars, swelling and skin disease can increase risk. Persistent drainage is important because it may increase the risk of deeper infection. Patients should not apply unprescribed powders, oils, antiseptics or home remedies.

Read Wound Care After Knee Replacement.

Stiffness and Limited Movement

Some early stiffness is expected. Persistent functional limitation may result from swelling, pain, preoperative stiffness, muscle weakness, delayed rehabilitation, excessive scar tissue, infection, instability or component position. Selected patients may require manipulation under anaesthesia, scar-tissue release or revision when a correctable cause exists.

Read Stiffness After Knee Replacement Surgery.

Persistent or Unexplained Pain

Most patients obtain meaningful pain relief, but some continue to have pain or develop new pain later. Causes include infection, stiffness, instability, loosening, patellar problems, tendon irritation, nerve pain, complex regional pain syndrome, hip or spine disease, or an expectation mismatch. Revision should not be performed for pain alone without a treatable diagnosis.

Read Pain After Knee Replacement Surgery.

Instability, Buckling and Ligament Problems

Early buckling may occur from quadriceps weakness, but recurrent shifting, giving way or a loose feeling can also indicate ligament imbalance, component position or wear. Instability may cause pain, falls, swelling and loss of confidence. Treatment ranges from rehabilitation to revision, depending on whether the cause is muscular or mechanical.

Fracture During or After Surgery

A fracture can occur during implantation or later after a fall. Risk is higher with osteoporosis, severe deformity, revision surgery and certain bone defects. Treatment depends on fracture location, implant stability and bone quality and may require fixation or revision components. Sudden pain, deformity or inability to bear weight after a fall requires urgent X-rays.

Nerve or Blood-Vessel Injury

Temporary numbness beside the scar is common because small skin nerves are divided. Major nerve injury is uncommon but can cause foot weakness, altered sensation or neuropathic pain. Blood-vessel injury is rare but serious and may cause bleeding, reduced circulation or a cold pale foot. New foot-drop, progressive numbness, severe pain or circulation change requires prompt assessment.

Tendon and Kneecap Problems

The quadriceps tendon, patellar tendon and kneecap mechanism are essential for straightening the knee. Injury, fracture, maltracking, scar tissue or weakness can cause pain, extensor lag, catching or inability to perform a straight-leg raise. Some painless clicking is benign, but a pop followed by sudden loss of extension requires urgent review.

Implant Wear, Loosening and Mechanical Failure

Modern implants are durable, but polyethylene wear, loosening, bone loss, component breakage or instability can develop over time. These problems may cause new pain, swelling, reduced function or altered alignment. Routine follow-up and comparison of X-rays can identify changes before they become advanced. Read Loose Knee Implant Symptoms.

Anaesthetic and Medical Complications

Possible complications include medicine reactions, nausea, urinary retention, confusion, heart rhythm problems, heart attack, stroke, lung complications, kidney injury, uncontrolled blood sugar and pressure injury. The anaesthetic and medical team assess risk before surgery and plan monitoring, but risk cannot be reduced to zero. Optimisation may require postponing elective surgery until a condition is safer.

Falls and Loss of Independence

Early weakness, dizziness, sedating medicines, unfamiliar walking aids and stairs increase fall risk. A fall can damage the wound, tendon, bone or implant. Safe discharge planning includes walking-aid training, home preparation, lighting, bathroom support and caregiver availability. A shorter hospital stay is not useful if the home transition is unsafe.

Reoperation and Revision Surgery

A complication may require a return to theatre for wound treatment, fracture fixation, manipulation, tendon repair, infection surgery or revision replacement. Revision operations are generally more complex than first-time replacement and can have greater risks, longer recovery and less predictable outcomes. This possibility should be included in preoperative counselling without implying that revision is likely for every patient.

Factors That Can Increase Risk

Important factors include poorly controlled diabetes, smoking, anaemia, malnutrition, active infection, severe obesity, previous clots, untreated sleep apnoea, poor circulation, kidney or heart disease, immune suppression, skin wounds, osteoporosis, severe deformity, multiple previous operations and inadequate home support. These factors guide optimisation and consent; they do not automatically mean that surgery is impossible.

How Risk Is Reduced

Risk reduction may include confirming that replacement is genuinely indicated, treating skin or dental problems when relevant, controlling diabetes and blood pressure, correcting anaemia, stopping smoking, reviewing medicines, planning antibiotics and clot prevention, using sterile technique, reducing blood loss, beginning mobilisation when safe, protecting the wound and providing clear discharge instructions. No single measure or technology replaces the complete safety pathway.

Robotic, Mini-Subvastus, Partial, Bilateral and Revision Surgery

Robotic assistance supports planning and execution, while the mini-subvastus approach aims to preserve the quadriceps mechanism in suitable patients. Neither eliminates infection, clot, wound, pain or medical risk. Partial replacement can involve a smaller reconstruction but depends on correct disease selection. Bilateral and revision procedures often have greater physiological, mobility and reconstruction demands and require separate counselling.

Questions to Ask Before Surgery

Patients should ask why replacement is recommended, whether total or partial replacement is suitable, which individual risks matter most, what optimisation is required, how infection and clots will be prevented, what recovery support is available, which symptoms require urgent contact and what alternatives remain. The discussion should include realistic pain relief, movement and activity expectations.

When Prompt or Emergency Care Is Needed

Seek prompt assessment for wound drainage, spreading redness, increasing rest pain, fever, new calf pain or swelling, repeated buckling, sudden loss of movement, a fall, new foot weakness or inability to bear weight. Seek emergency care for chest pain, sudden breathlessness, coughing blood, fainting, uncontrolled bleeding, severe confusion or a cold pale or blue foot.

Questions Patients Commonly Ask

Is knee replacement a high-risk operation?

It is major surgery with recognised risks, but many patients undergo it safely after appropriate selection, optimisation and preventive care.

Can all complications be prevented?

No. Risk can be reduced but not eliminated completely.

Is warmth around the knee a complication?

Mild warmth can occur during healing. Increasing warmth with redness, drainage, pain or declining function needs review.

Does every blood clot cause calf pain?

No. Some clots cause few or no symptoms, which is why prevention and risk assessment matter.

Can infection happen years later?

Yes. Late infection is possible, although uncommon, and may present with pain, swelling or stiffness rather than fever.

Is numbness beside the scar nerve damage?

A small numb area is common from skin-nerve division. New foot weakness or progressive numbness is different and needs assessment.

Does robotic surgery remove surgical risks?

No. It assists planning and execution but does not eliminate biological, medical or rehabilitation complications.

Is partial replacement always safer?

It may involve a smaller reconstruction in selected patients, but inappropriate selection creates its own risks and it is not suitable for all arthritis patterns.

Does persistent pain mean the operation failed?

Not automatically. The pain source must be diagnosed before conclusions or revision decisions are made.

Can a complication require revision surgery?

Yes, but revision is reserved for specific problems where expected benefit justifies the additional risk.

Clinical References and Further Reading

NICE NG157: Shared Decision-Making, Risks and Recovery After Joint Replacement

AAOS OrthoInfo: Total Knee Replacement

AAOS OrthoInfo: Revision Total Knee Replacement

About Dr. Mayur Rabhadiya

Dr. Mayur Rabhadiya is an Orthopedic and Joint Replacement Surgeon in Mumbai. His focused knee practice includes total, partial and minimally invasive mini-subvastus robotic knee replacement, complication assessment and revision planning. His qualifications are MBBS, D’Ortho, DNB (Orthopedics), MNAMS (Orthopedics) and FIJR (Robotic & Navigation).

Last medically reviewed: 24 July 2026. Medical reviewer: Dr. Mayur Rabhadiya.

Book a Knee Replacement Risk Consultation

Patients seeking individual risk assessment, a second opinion or review of a postoperative concern can consult Dr. Mayur Rabhadiya in Ghatkopar East or Ghatkopar West, Mumbai. Call or WhatsApp +91 84249 03913 or +91 96113 30063, or use the orthopedic appointment page.

Medical Disclaimer

This guide provides general education and does not estimate an individual patient’s surgical risk. Risk counselling, optimisation and treatment decisions require medical assessment and review of the planned procedure.