Knee replacement is one of the most common surgeries in the UK. Understanding your options, expected outcomes, and rehabilitation requirements helps you make an informed decision.
When knee replacement is appropriate
Replacement is typically considered when: arthritis has progressed significantly (visible on X-ray), conservative treatment (physiotherapy, medications, weight loss, activity modification) has been tried and failed to relieve pain, pain significantly limits daily activities (walking, stairs, work), and you're motivated to do rehabilitation afterward.
Age is not a barrier. Younger patients (even 40-50s) can have knee replacement if indicated, though results might be slightly different (younger people are more active post-op).
Types of knee replacement
Total knee replacement (TKR) replaces the entire joint surface: femur, tibia, patella. Most common, excellent evidence, reliable outcomes.
Partial (unicompartmental) knee replacement replaces only one compartment (medial or lateral). Suitable if arthritis is isolated to one compartment and other compartments are healthy. Less invasive, faster recovery, but fewer people qualify.
Revision knee replacement is when a previous replacement wears out or fails. More complex surgery, slightly worse outcomes, but still significantly helps most people.
Expected outcomes and timeline
Most people experience: significant pain relief within weeks, improved function (walking, stairs, standing) improving over months, near-normal gait at 3 months, maximum improvement at 6-12 months.
Pain relief: 85-90% of people report significant pain relief. Some residual pain is common but manageable. Complete pain-free result is less common than people expect.
Activity level: most people return to walking, light exercise, daily activities. Heavy impact activities (running, competitive sports) are usually not recommended, though some people do them.
Implant lifespan: modern knee replacements last 15-20+ years. Younger patients might need revision eventually. Older patients (70+) usually wear out their replacement.
Rehabilitation is critical
The first 6 weeks of physiotherapy is where outcomes are determined. Consistent movement, exercises, and weight-bearing on the leg (even when painful) drive recovery. Patients who do their physio intensively recover better than those who don't.
Expect: pain-free movement increasing weekly, weight-bearing increasing, swelling gradually reducing, walking distance increasing. This isn't instant; it takes weeks.
Psychological challenge: after weeks of pain-relieving surgery, you're not instantly better. Pain and limitation persist for weeks to months. Many patients get frustrated mid-recovery and reduce their rehab effort, which slows progress.
Complications and risks
Infection: uncommon (less than 1%) but serious. If you develop fever and wound drainage post-op, seek immediate medical attention.
Deep vein thrombosis (blood clot in leg): occurs in 1-2% even with blood thinner prevention. Signs: calf swelling, warmth, pain, shortness of breath. Urgent medical attention needed.
Stiffness: sometimes the knee doesn't regain full range of motion. Aggressive physiotherapy early prevents this, but some people remain slightly stiff.
Implant failure: loosening (gradual) or fracture (rare). Loosening typically requires revision surgery.
NHS vs private knee replacement
NHS: excellent outcome data, experienced surgeons, zero cost. Waiting times can be long (6-12 months), and physiotherapy access post-op varies.
Private: faster scheduling (weeks not months), more input on surgeon choice, potentially more physio input. Cost: £10,000-15,000 surgery plus physio fees.
Choose private if: waiting is significantly affecting your life, you have the financial means, you want specific surgeon input. Choose NHS if: you can wait, you value zero financial outlay, your local NHS outcomes are good.
Pre-surgery optimization
Weight: if overweight, losing weight before surgery improves outcomes. Every kg of weight loss reduces knee stress. You don't need to be perfect weight; any weight loss helps.
Smoking: quit before surgery. Smoking increases infection risk and slows wound healing. Quitting even 4 weeks before surgery improves outcomes.
Exercise: pre-operative strength and fitness improve post-operative outcomes. Walking, strengthening thighs and hips pre-op means faster recovery.
Mental preparation: understanding what recovery involves, having realistic expectations, planning for time off work and support from family—all improve outcomes. Patients who are mentally prepared handle recovery better.
What affects outcomes most
Surgeon experience matters, but rehabilitation effort matters more. A brilliant surgeon's work can be undermined by poor post-op care. A good surgeon with a committed patient doing intense physiotherapy gets better results than a great surgeon with a patient who doesn't do physio.
Age: younger patients tend to do slightly better and are more active post-op. Older patients (70+) still do very well, but might not return to high-impact activities.
Expectations: patients expecting pain-free perfection sometimes report disappointment. Patients expecting significant improvement often report satisfaction even with slight residual symptoms.
Realistic timeline for return to function
Week 1-2: painful, limited movement, swollen leg, walking with crutches or walker.
Week 4-6: gradual improvement, crutches down to one crutch, sleeping better, some driving possible if not on strong pain meds.
Week 8-12: most pain resolved, good movement, walking without crutches, returning to light activities.
Month 3-6: significant improvement, nearly normal gait, returning to exercise and most activities, minor swelling may persist.
Month 6-12: maximum improvement, can typically return to most activities (walking, golf, light sports), some caution with high-impact (running, competitive sports).
Beyond 12 months: continued improvement is possible, but most gains occur in first year.
When not to have knee replacement
If you haven't tried or completed physiotherapy, conservative treatment should come first. If you haven't lost weight (if overweight) or tried activity modification, do those first.
If your pain is primarily in the back, hip, or foot, not the knee joint itself, replacement won't help (you'll still have pain). Get the right diagnosis first.
If you have significant psychiatric illness or cognitive impairment limiting your ability to do rehabilitation, outcomes are worse. Psychological support might help.
If you have unrealistic expectations (expecting 100% pain-free result, expecting to return to running), you'll be disappointed. Make sure expectations are realistic before deciding.
Questions for your surgeon before committing
What is your complication rate? How many revisions have you done? What's your preferred surgical approach and why? What does my recovery timeline realistically look like? Can I return to my specific desired activities? What happens if I'm still in pain after rehabilitation completes? What would revision surgery involve?
A surgeon who can answer these specifically and realistically is one you likely trust for this decision.