Knee Replacement Recovery, Infection Risk and Implant Life

Knee replacement recovery is fast when the patient is prepared well. In Dr. Rakesh Mahajan's pathway, the patient is admitted, operated on the next day, walking with a walker the day after, climbing stairs without support by the fourth or fifth day and home by the sixth. Two factors shape the course: infection control before surgery and the strength of the quadriceps muscles.

Whether the knee is replaced robotically or conventionally, as the complete guide to robotic knee replacement explains, the patient's journey around the operation is the same. Dr. Rakesh Mahajan, Vice Chairman & HOD - Orthopedics, BLK-Max Super Speciality Hospital, New Delhi, India, set out that journey in practical detail: how he screens out infection risk, what the first week looks like, how long modern implants last, which sports are safe afterwards, and how people in their forties can protect their knees so that replacement comes as late as possible.

Preventing infection after knee replacement

Dr. Mahajan prevents infection after knee replacement largely before admission, by controlling blood sugar and clearing urinary infection. Infection of the implant is the complication every knee surgeon works hardest to prevent, because it can undo an otherwise perfect operation. Dr. Mahajan's approach is to deal with the risk before the patient is admitted. He identifies two very common causes of infection after total knee replacement: uncontrolled diabetes and urinary infection.

Blood sugar: the HbA1c threshold

For every diabetic patient, glycated haemoglobin (HbA1c, a measure of average blood sugar over the previous two to three months) is checked before admission. Dr. Mahajan's thresholds are firm:

• HbA1c of 9 or above: the patient is not fit for knee replacement. At that level, he said, the infection rate rises significantly.
• Target before surgery: an HbA1c below 7, or at most 7.5.
• Anything above the target: the patient is referred to a physician to bring the HbA1c into range, and surgery is scheduled only after that.

Urinary infection: screen and clear

The other common source of infection after surgery is the urinary tract. Before admission, every patient has a routine urine examination and a urine culture and sensitivity test. If the urine shows more than about 10 pus cells, the patient is referred to a nephrologist for treatment and clearance before surgery. Guidelines distinguish symptomatic from asymptomatic findings: a symptomatic urinary infection should be treated before surgery, but bacteria in the urine without symptoms need not be treated before joint replacement, because treatment has not been shown to reduce implant infection.

Knee replacement recovery timeline: the first week

In Dr. Mahajan's pathway, the patient goes home on day six of the stay, counted from admission, walking without support. He describes recovery as very good, with quality of life improving almost immediately. He counts the timeline from the day of admission:

1. Day 1: admission.
2. Day 2: surgery.
3. Day 3: the patient starts walking with a walker under the guidance of a physiotherapist.
4. Days 4 and 5: the patient climbs stairs and walks without any support.
5. Day 6: the patient can go home without support.

That pace, in his words, is the beauty of the operation. It is also the expectation he sets with patients before surgery.

Why the quadriceps decide the outcome

The factor Dr. Mahajan emphasises most in recovery is the quadriceps, the large muscle group at the front of the thigh that straightens the knee and stabilises it with every step. If the quadriceps are weak, the patient takes longer to recover; if their power is good, the patient recovers very fast.

Physiotherapy after surgery is therefore built around strengthening the quadriceps, using isokinetic exercises (resistance exercises performed at a controlled, constant speed through the range of motion). Once the muscles are well developed, the patient does very well.

How long does a knee replacement last?

With the latest implants, Dr. Mahajan has patients more than 15 years after surgery who are doing perfectly well, and the incidence of loosening or other problems is less than 2%. Implant longevity has improved substantially across generations: he recalls that the earlier second-generation implants had a shorter life of about 12 to 15 years, and patients did return for further surgery.

Pooled registry data put long-term survival in context: around 82% of total knee replacements are still functioning 25 years after surgery.

Which sports are safe after knee replacement?

Walking, cycling, swimming and light uphill activity are recommended after knee replacement; contact games and high-activity games such as tennis and badminton are not. Because some patients develop badly damaged knees in their thirties, the question of returning to sport after replacement is a real one. Dr. Mahajan's answer distinguishes clearly between activities.

Recommended:

• Walking
• Cycling
• Swimming
• Light uphill activity

Not recommended:

• Contact games. They cause more wear and tear on the implant components, and that wear leads to aseptic loosening (loosening of the implant without infection).
• High-activity games such as tennis and badminton. Sports that involve frequent jumping sit between the two groups, but he does not recommend them, and many studies advise avoiding them.

Patients who keep to the recommended activities can, in his words, lead a good, healthy life.

How to protect your knees before arthritis starts

Regular walking or cycling, strong quadriceps and a healthy body weight are the core of Dr. Mahajan's advice for protecting the knees. Asked what someone in their forties should do to delay knee degeneration for as long as possible, his advice was simple and specific.

Stay active, however busy you are. The two best exercises for the knee are walking, for a minimum of half an hour, and cycling, including on a static cycle. Both strengthen the quadriceps, and strong quadriceps keep the knee much healthier. Once the quadriceps weaken, the pain keeps increasing.

Control body weight. He advises eating healthily and not being overweight. Someone who is overweight should shift the diet towards more protein and fewer carbohydrates, and walk wherever possible instead of taking the car.

Know when to stop running. For a person with no knee pain or knee problem, any activity is fine, including running, jogging and tennis. Once knee arthritis starts, however, he advises stopping jogging and running and walking instead, and climbing no more than two floors of stairs, because more than that starts to damage the knee further.

Who develops knee arthritis early

Knee degeneration is more common in women, which Dr. Mahajan links to the hormonal changes after the age of 45 to 50. Knee osteoarthritis rises sharply in women after menopause, and loss of oestrogen is thought to contribute, although the mechanism is not settled. As the cartilage wears, pain increases and movement falls; less movement weakens the muscles further, and a vicious cycle sets in.

Genetic factors also play a part, as do metabolic and autoimmune diseases. In patients with diabetes, hypothyroidism or rheumatoid arthritis, the knee is affected much earlier. Dr. Mahajan sees patients whose knees are badly damaged between the ages of 35 and 40 because of these conditions. His earlier masterclass on joint pain in the younger population covers this group in more depth.

Knee lubrication: exercise first, supplements second

Exercise is the first way to improve knee lubrication, and supplements come second, with limited guideline support. A doctor from Tanzania raised the question in the Live Discussion for this masterclass, asking how to ensure efficient lubrication of the knee joint. Dr. Mahajan's first answer is exercise: regular knee exercises, given sufficient time, produce natural lubrication. Where that is not enough, he uses a group of products known as nutraceuticals that help promote lubrication.

He described how the options have evolved:

• Earlier options: chondroitin sulphate and glucosamine were the basic supplements.
• Collagen supplements: collagen types 1, 2 and 3 are now used in orthopaedics. For the knee, collagen type 2 is the relevant one, because it is the main collagen of knee cartilage, and it is available in formulations combined with other agents intended to promote cartilage cell formation.
• For tendons: collagen types 1 and 3, because tendons are mainly composed of those collagens.

The evidence for these products is limited. The American College of Rheumatology guideline recommends against glucosamine and chondroitin for knee osteoarthritis, and NICE advises against offering glucosamine.

Knee replacement during pregnancy: why surgery waits

Knee replacement is an elective operation, so it can wait. Asked how he manages a pregnant patient whose knee would otherwise need replacement, Dr. Mahajan was clear that the pregnancy is the first priority. Until it is over, he gives only minimal, first-aid-type treatment:

• Cold packs and cryotherapy
• Physiotherapy
• An offloader brace, which shifts load away from the damaged side of the knee to relieve pain
• Exceptionally, for severe pain, a steroid injection

Once the pregnancy is over, surgery can proceed.

Where this fits

This article covers the patient's side of the operation. The technical side, from CT planning and haptic-guided cuts to the trial evidence comparing robotic and conventional surgery, is in the companion article on how robot-assisted knee replacement works. The costs of the operation are on the total knee replacement cost page, and for both knees at once, the bilateral total knee replacement cost page. For younger patients with knee injuries rather than arthritis, Dr. Vipin Maheshwari's guide to knee and shoulder arthroscopy covers ligament and meniscus surgery.