Knee Replacement Surgery: Complete Guide for Osteoarthritis

What Is Knee Replacement Surgery?

Knee replacement surgery, also called total knee arthroplasty (TKA), is a surgical procedure that replaces the damaged surfaces of the knee joint with artificial components made of metal alloys and medical-grade plastic. It is primarily performed to treat severe osteoarthritis when conservative treatments no longer provide adequate pain relief.

Knee osteoarthritis is a degenerative condition where the protective cartilage that cushions the ends of the bones gradually wears away. As the cartilage deteriorates, the bones begin to rub against each other, causing pain, stiffness, swelling, and reduced mobility. When this damage becomes severe and significantly impacts quality of life, knee replacement surgery offers a solution by creating new, smooth joint surfaces.

The knee joint is one of the largest and most complex joints in the human body. It consists of three compartments: the medial (inner) compartment, the lateral (outer) compartment, and the patellofemoral (kneecap) compartment. During a total knee replacement, all three compartments are typically resurfaced. In some cases, if damage is limited to one compartment, a partial (unicompartmental) knee replacement may be an option.

Total knee replacement has been performed for over 50 years and is one of the most successful and commonly performed orthopedic procedures worldwide. According to global statistics, approximately 1 million knee replacements are performed annually in the United States alone, with the number continuing to rise as populations age and the procedure's success becomes more widely recognized.

Types of Knee Replacement Surgery

There are several types of knee replacement procedures, each suited to different situations:

• Total Knee Replacement (TKR/TKA): The most common procedure, replacing all three compartments of the knee joint. Suitable for patients with widespread osteoarthritis affecting the entire joint.
• Partial (Unicompartmental) Knee Replacement: Replaces only the damaged compartment, preserving healthy bone and cartilage. Offers faster recovery but is only suitable for patients with localized damage.
• Bilateral Knee Replacement: Replacement of both knees, either simultaneously (same surgery) or staged (separate surgeries). The approach depends on patient health and surgeon recommendation.
• Revision Knee Replacement: Surgery to replace a worn or failed previous knee implant. More complex than primary replacement due to bone loss and scar tissue.

Understanding Knee Implant Components

A total knee replacement prosthesis consists of three main components that work together to recreate the smooth movement of a healthy knee:

The femoral component is a curved metal piece that fits over the end of the thighbone (femur). It is typically made from a cobalt-chromium alloy, chosen for its strength, durability, and biocompatibility. The femoral component has a smooth, polished surface that allows smooth gliding motion.

The tibial component consists of a flat metal platform that fits on top of the shinbone (tibia). This component is usually made from titanium alloy and includes a polyethylene (medical-grade plastic) insert that sits on top, providing a smooth cushion between the metal components.

The patellar component is a dome-shaped plastic piece that resurfaces the underside of the kneecap (patella). Not all knee replacements include this component; your surgeon will determine if it's necessary based on the condition of your kneecap.

Who Needs Knee Replacement Surgery?

Knee replacement surgery is recommended for patients with severe knee osteoarthritis who experience significant pain that limits daily activities, have not responded adequately to conservative treatments, and whose quality of life is substantially affected. The decision is based on symptoms and functional limitations rather than age or X-ray findings alone.

The decision to undergo knee replacement surgery is highly personal and should be made jointly between you and your orthopedic surgeon after careful consideration of your symptoms, lifestyle, and treatment goals. While there is no absolute age limit for knee replacement, most candidates are between 50 and 80 years old. However, younger patients with severe osteoarthritis may also be appropriate candidates.

Before recommending surgery, your healthcare team will typically try various conservative treatments. These non-surgical approaches may include physical therapy to strengthen the muscles around the knee, weight management to reduce joint stress, anti-inflammatory medications, pain relievers, corticosteroid injections, hyaluronic acid injections, and assistive devices like knee braces or walking aids. Surgery is generally considered when these measures no longer provide adequate relief.

Indications for Knee Replacement

Your doctor may recommend knee replacement surgery if you experience:

• Severe knee pain that limits daily activities such as walking, climbing stairs, or getting up from chairs
• Moderate to severe pain at rest, including pain that disrupts sleep
• Chronic knee inflammation and swelling that doesn't improve with rest or medications
• Significant knee stiffness that limits your ability to bend or straighten your knee
• Knee deformity - bowing in or out of the knee
• Failure of conservative treatments to provide adequate relief after an appropriate trial period
• X-ray evidence of severe joint damage with loss of cartilage

Who May Not Be a Good Candidate

While knee replacement is highly successful for most patients, certain factors may affect candidacy or increase surgical risks:

• Active infection anywhere in the body, particularly in the knee joint
• Severe peripheral vascular disease affecting blood supply to the leg
• Significant medical conditions that increase surgical risk to unacceptable levels
• Unrealistic expectations about surgical outcomes
• Inability to participate in post-operative rehabilitation

How Should You Prepare for Knee Replacement Surgery?

Preparation for knee replacement surgery includes attending a preoperative consultation, completing required medical tests, using antibacterial wash before surgery, preparing your home for recovery, practicing with mobility aids, stopping certain medications, and following fasting instructions. Quitting smoking and optimizing overall health significantly improves outcomes.

Proper preparation is essential for a successful knee replacement surgery and smooth recovery. The preparation process typically begins several weeks before your scheduled surgery date. Your healthcare team will provide specific instructions, but understanding the general preparation process can help you feel more confident and ready.

Preoperative Consultation

Before your surgery date, you will attend one or more preoperative appointments. During these visits, your medical team will explain the surgical procedure in detail, discuss what to expect during recovery, and answer any questions you may have. This is an excellent opportunity to address any concerns and ensure you have realistic expectations about the surgery and rehabilitation process.

Your healthcare team will review your complete medical history, including all current medications, supplements, and any allergies. Certain medications, particularly blood thinners and some anti-inflammatory drugs, may need to be stopped before surgery. Never stop any medication without explicit instructions from your healthcare provider.

Medical Tests and Evaluations

You will likely need to complete several tests before surgery to ensure you are medically fit for the procedure. These typically include blood tests to check your overall health and detect any conditions that might affect surgery, an electrocardiogram (ECG) to evaluate heart function, a chest X-ray to assess lung health, and possibly a urinalysis to rule out infection.

If you have other health conditions such as diabetes, heart disease, or lung problems, your surgeon may request clearance from other specialists to ensure these conditions are well-controlled before surgery.

Reducing Infection Risk

Infection is one of the most serious potential complications of joint replacement surgery. To minimize this risk, you will be asked to shower with a special antibacterial soap (such as chlorhexidine) for several days before surgery. This helps reduce the number of bacteria on your skin. Follow your healthcare provider's specific instructions carefully regarding when and how to use this soap.

Before surgery, inform your medical team of any signs of infection anywhere in your body, including dental problems, skin infections, or urinary tract infections. These should be treated before proceeding with joint replacement surgery.

Lifestyle Modifications

If you smoke, quitting before surgery is one of the most important things you can do to improve your outcome. Smoking impairs wound healing, increases infection risk, and can affect bone health. Research shows that stopping smoking at least 4-8 weeks before surgery significantly reduces complications. Similarly, reducing or eliminating alcohol consumption before surgery can help improve healing and reduce complications.

If you are overweight, even modest weight loss before surgery can reduce stress on your new joint and improve surgical outcomes. Your medical team may recommend working with a dietitian or participating in a weight management program before surgery.

Physical Preparation

Strengthening your body before surgery can make recovery easier and faster. Your surgeon or physical therapist may recommend specific exercises to strengthen the muscles around your knee and improve your overall fitness. Strong quadriceps (front thigh muscles) and good upper body strength will help you with mobility after surgery.

Practice walking with crutches or a walker before your surgery. You will need to use these aids for several weeks after the procedure, and being comfortable with them beforehand will make your initial recovery much smoother. You can often obtain or purchase crutches from a medical supply store or pharmacy.

Preparing Your Home

Making modifications to your home before surgery will make your recovery safer and more comfortable. Consider the following preparations:

• Remove trip hazards: Secure or remove loose rugs, electrical cords, and any clutter from walkways
• Rearrange frequently used items: Place items you use daily at arm level to avoid bending or reaching
• Install safety equipment: Consider grab bars in the bathroom, a raised toilet seat, and a shower chair or bench
• Prepare a recovery area: Set up a comfortable space with everything you need within reach, ideally on the main floor to avoid stairs
• Stock up on supplies: Prepare meals that can be frozen and reheated, and ensure you have enough medications and supplies
• Arrange help: Organize assistance from family or friends for the first few weeks after surgery, or arrange for professional home care if needed

Fasting Before Surgery

You will need to fast (not eat or drink) for a specified period before surgery, typically 6-12 hours. This is essential for safe anesthesia administration. Your surgical team will provide specific instructions about when to stop eating and drinking, and which medications you should take with a small sip of water on the morning of surgery.

How Is Knee Replacement Surgery Performed?

During knee replacement surgery, the surgeon makes an incision over the knee, removes damaged cartilage and bone from the joint surfaces, prepares the bone to receive the implant components, secures the metal and plastic prosthesis in place, and closes the incision. The procedure typically takes 1-2 hours under regional or general anesthesia.

Understanding what happens during knee replacement surgery can help reduce anxiety and prepare you mentally for the procedure. While surgical techniques continue to evolve with advances in technology and research, the fundamental principles of the operation remain consistent.

Anesthesia Options

Before surgery begins, you will receive anesthesia to ensure you are comfortable and pain-free during the procedure. There are two main options:

Regional anesthesia (spinal or epidural) numbs the lower body while you remain awake or lightly sedated. Many patients and surgeons prefer this option because it typically results in better pain control immediately after surgery, lower risk of certain complications, and faster initial recovery. You may receive sedation so you sleep through the procedure even though you are not under general anesthesia.

General anesthesia puts you completely to sleep during the surgery. This may be recommended in certain situations or if regional anesthesia is not suitable for you. Your anesthesiologist will discuss the best option for your specific situation.

The Surgical Procedure

The surgery itself typically follows these steps:

Step 1: Incision. The surgeon makes an incision over the front of the knee, typically 15-25 centimeters (6-10 inches) long. In some cases, minimally invasive techniques with smaller incisions may be used, though this depends on various factors including your anatomy and the surgeon's expertise.

Step 2: Exposing the joint. The surgeon carefully moves muscles and tendons aside to expose the knee joint. The kneecap (patella) is typically moved to the side to allow access to the joint surfaces.

Step 3: Removing damaged surfaces. Using specialized cutting guides and instruments, the surgeon precisely removes the damaged cartilage and a small amount of underlying bone from the end of the femur (thighbone), the top of the tibia (shinbone), and often the underside of the patella.

Step 4: Preparing the bone. The remaining bone surfaces are carefully shaped to fit the prosthetic components exactly. Precise bone cuts are essential for proper implant alignment and long-term function.

Step 5: Placing the implant. The metal femoral component is attached to the end of the femur, and the tibial component is secured to the top of the tibia. A medical-grade plastic spacer is inserted between the metal components to create a smooth gliding surface. If the patella is being resurfaced, a plastic button is attached to its undersurface.

Step 6: Testing the joint. Before closing, the surgeon tests the knee through its full range of motion to ensure proper alignment, stability, and function of the new joint.

Step 7: Closing the incision. The incision is closed with sutures or staples, and a sterile bandage is applied. A drain may be placed to remove excess fluid, though this is less common with modern techniques.

Types of Implant Fixation

Knee implants can be secured to the bone in two ways:

Cemented fixation uses a special bone cement (polymethylmethacrylate) to bond the implant components to the bone. This provides immediate stability and is the most common method used worldwide.

Cementless fixation uses implants with a special porous surface that allows bone to grow into and around the components over time. This approach may be preferred in younger, more active patients with good bone quality.

Hybrid fixation combines both methods, typically using cement for the tibial component and cementless fixation for the femoral component.

High Tibial Osteotomy: An Alternative for Some Patients

In some cases, particularly for younger patients with osteoarthritis affecting only one side of the knee, an alternative procedure called high tibial osteotomy may be considered. This procedure does not replace the joint but instead realigns the leg by removing a wedge of bone from the tibia. This shifts weight-bearing away from the damaged area to healthier cartilage. While this can delay the need for knee replacement, it may not be permanent, and many patients eventually require knee replacement later.

What Happens After Knee Replacement Surgery?

After knee replacement surgery, you will typically stay in hospital for 1-3 days. Physical therapy begins within 24 hours to restore movement. Pain is managed with medications, and you will use crutches or a walker for several weeks. Most patients return to normal activities within 6-12 weeks, though complete recovery may take up to a year.

Recovery from knee replacement surgery is a gradual process that requires patience, dedication to rehabilitation, and realistic expectations. Understanding what to expect at each stage can help you prepare and stay motivated throughout your recovery journey.

Immediately After Surgery

You will wake up in the recovery room where medical staff will monitor your vital signs and manage any immediate post-operative symptoms. You may feel groggy from the anesthesia and may experience some nausea. Pain medication will be provided to keep you comfortable.

Once stable, you will be transferred to your hospital room. Modern recovery protocols, often called "enhanced recovery" or "fast-track" programs, encourage early mobilization. A physical therapist will typically visit you within 24 hours of surgery to help you stand and take your first steps with a walker or crutches.

Hospital Stay

Most patients stay in the hospital for 1-3 days after knee replacement surgery. During this time, you will receive pain medication, antibiotics to prevent infection, and blood thinners to reduce the risk of blood clots. Physical therapy sessions will continue, focusing on walking, knee bending exercises, and transferring safely between positions.

Before discharge, you must demonstrate that you can walk safely with an assistive device, manage stairs if necessary, bend your knee adequately, and control your pain with oral medications. A discharge planner will help arrange any needed equipment and home care services.

Pain Management

You will experience pain after surgery, which is normal and expected. Effective pain management is crucial because it allows you to participate actively in rehabilitation. Your pain management plan may include a combination of oral pain medications (including opioids for the first few weeks), non-opioid pain relievers such as acetaminophen, anti-inflammatory medications when appropriate, ice therapy to reduce swelling, and elevation of the leg.

Follow your prescribed pain medication schedule, especially in the first week. Taking medication regularly prevents pain from becoming severe, which makes it harder to control. As you progress through recovery, your need for pain medication will decrease, and you should work with your healthcare team to gradually reduce and eventually stop opioid medications.

Managing Swelling

Swelling is common after knee replacement and can persist for several months. Managing swelling is important for comfort and mobility. Effective strategies include elevating your leg when resting (with the knee higher than your heart), applying ice packs wrapped in a towel for 15-20 minutes several times daily, wearing compression stockings as recommended, and moving regularly to promote circulation.

Using Mobility Aids

You will need to use a walker or crutches for several weeks after surgery. Most patients use a walker initially, then progress to crutches or a cane as strength and balance improve. Follow your physical therapist's guidance on how to use these aids correctly and when to transition between them. Most patients no longer need walking aids by 4-6 weeks after surgery.

Rehabilitation Program

Physical therapy is perhaps the most important factor in achieving a successful outcome from knee replacement surgery. Your rehabilitation program will progress through several phases, beginning immediately after surgery and continuing for several months.

In the early phase (weeks 1-2), therapy focuses on basic mobility, gentle range of motion exercises, and reducing swelling. You will learn to perform exercises independently at home and gradually increase walking distance.

During the intermediate phase (weeks 3-6), exercises become more challenging. You will work on increasing knee flexibility, strengthening the quadriceps and other leg muscles, improving balance, and progressing from walker to cane.

In the advanced phase (weeks 6-12 and beyond), therapy focuses on returning to normal activities. This includes advanced strengthening exercises, higher-level balance training, and activity-specific training based on your goals.

Recovery Milestones

While everyone recovers at their own pace, here are typical milestones:

What Are the Risks and Complications?

While knee replacement is generally safe, potential complications include infection (1-2%), blood clots (deep vein thrombosis), nerve or blood vessel damage, implant problems (loosening or wear), stiffness, and persistent pain. Serious complications are uncommon, and preventive measures significantly reduce these risks.

Knee replacement surgery is one of the most successful orthopedic procedures, but like any surgery, it carries some risks. Understanding these potential complications helps you make an informed decision and recognize warning signs that require medical attention.

Infection

Infection is one of the most serious complications of joint replacement surgery, occurring in approximately 1-2% of cases. Infections can occur at the wound site (superficial) or deep within the joint (deep infection). Superficial infections are usually treated successfully with antibiotics, while deep infections may require additional surgery and prolonged antibiotic treatment.

Warning signs of infection include increasing pain after initial improvement, fever, redness, warmth, or swelling around the knee, wound drainage, and feeling generally unwell. Contact your healthcare provider immediately if you experience these symptoms.

To minimize infection risk, antibiotics are given before and after surgery, sterile surgical technique is used, and patients are screened and treated for any existing infections before surgery.

Blood Clots

Deep vein thrombosis (DVT), or blood clots in the leg veins, is a concern after any major surgery. These clots can be dangerous if they travel to the lungs, causing a pulmonary embolism. Preventive measures include blood-thinning medications, compression stockings, early mobilization, and mechanical compression devices during and after surgery.

Signs of a blood clot include calf pain or tenderness, swelling in the leg or ankle, warmth and redness in the affected area, and shortness of breath or chest pain (if a clot reaches the lungs). Seek immediate medical attention if you experience these symptoms.

Nerve and Blood Vessel Injury

Nerves and blood vessels around the knee can occasionally be damaged during surgery. This is uncommon but can cause numbness, weakness, or circulation problems. Minor nerve injury causing numbness around the incision is relatively common and usually improves over time.

Implant Problems

While modern implants are highly durable, problems can occur including implant loosening over time (particularly with very active patients or those with poor bone quality), implant wear (the plastic bearing surface gradually wears down), instability (the knee feels unstable or gives way), and misalignment (improper positioning affecting function).

Stiffness

Some patients develop stiffness that limits knee movement, a condition called arthrofibrosis. This is usually prevented with early, consistent rehabilitation. In severe cases, a procedure called manipulation under anesthesia may be needed to restore movement.

Persistent Pain

A small percentage of patients (approximately 10-15%) experience persistent pain after knee replacement despite no identifiable cause. Research into this problem continues, but contributing factors may include nerve sensitivity, patient expectations, and psychological factors.

What Follow-Up Care Is Needed?

Follow-up care includes a wound check at 2-3 weeks for suture removal, progress evaluations at 6 weeks and 3 months, and annual check-ups to monitor implant function. Regular follow-up helps detect any problems early when they are most treatable.

After discharge from the hospital, you will have several follow-up appointments to monitor your recovery and ensure your new knee is functioning well. These appointments are important even if you feel you are recovering well.

Initial Follow-Up Visits

Your first post-operative visit is typically scheduled 2-3 weeks after surgery. At this appointment, your surgeon will examine the wound, remove any staples or sutures, check your range of motion and strength, review your progress with physical therapy, and adjust medications as needed.

Additional visits are usually scheduled at 6 weeks and 3 months post-surgery to assess your continued progress and address any concerns. X-rays may be taken to confirm proper implant positioning.

Long-Term Follow-Up

Even after you have fully recovered, regular follow-up is important to monitor the long-term health of your knee replacement. Most surgeons recommend annual check-ups, or at minimum, visits every 2-3 years. These visits typically include a physical examination, assessment of knee function, and X-rays to check for any signs of implant wear or loosening.

How Can You Participate in Your Care?

Active participation in your care improves outcomes. This includes understanding your surgery and recovery expectations, asking questions, following rehabilitation instructions carefully, reporting any concerns promptly, and making informed decisions about your treatment options.

Research consistently shows that patients who are actively engaged in their healthcare achieve better outcomes. This is particularly true for knee replacement surgery, where your participation in rehabilitation and self-care is essential for success.

Understanding Your Treatment

Take time to learn about your condition and treatment options. Ask your healthcare team questions about anything you don't understand. It's helpful to bring a family member or friend to appointments to help remember information and ask additional questions.

Communication with Your Healthcare Team

Open communication with your healthcare providers is essential. Let them know about your pain levels, functional progress, any concerns or new symptoms, and your goals and expectations. Don't hesitate to speak up if something doesn't seem right or if you're struggling with any aspect of recovery.

Informed Consent

Before any surgery, you have the right to receive complete information about the procedure, its benefits, risks, and alternatives. You must give your informed consent before the surgery can proceed. This means you understand what is being proposed and agree to the treatment. You also have the right to decline surgery or seek a second opinion at any time.