Knee Replacement — What Older Patients Really Need to Know

Total knee replacement replaces the damaged joint surfaces between the femur, tibia, and—if necessary—the patella with metal and plastic implants. Unlike in hip replacement surgery, the patient’s own bone is not completely replaced; rather, only the worn-out joint surfaces are removed and implants are placed. Depending on the type of prosthesis, some of the collateral ligaments and cruciate ligaments are preserved.

There are two main types:

Total Knee Arthroplasty (TKA)

The standard procedure for advanced knee osteoarthritis in older patients involving multiple compartments. All three bone surfaces are covered by implants. Suitable for long-term weight-bearing and functionally well-established.

Sled prosthesis (unicondylar partial knee replacement)

In cases of isolated osteoarthritis affecting only one part of the joint (usually the medial side), only that part is replaced. This is a less invasive procedure that preserves knee mechanics and allows for faster rehabilitation. Prerequisites: intact collateral ligaments, a stable joint on the opposite side, and no inflammatory joint disease.

The choice between a partial and total knee replacement is a decision made by an orthopedic specialist, taking into account the individual pattern of osteoarthritis, the stability of the joint, and the patient’s anatomy. Both procedures are highly successful when properly indicated.

→ For an overview of joint replacement in older adults: Joint Replacement in Older Adults.

A key difference that many patients underestimate: Rehabilitation after total knee replacement is significantly more demanding than after total hip replacement for patients aged 80 and older. The reasons are biomechanical and anatomical:

• Joint complexity: The knee is mechanically more complex than the ball-and-socket hip joint. It moves in multiple planes simultaneously.
• Connective tissue and scar formation: The knee is more prone to scarring (arthrofibrosis) after surgery, which can limit mobility if flexion is not consistently worked on.
• Pain perception: Knee pain after surgery is typically more intense and lasts longer than after a hip TEP.
• Musculature: The thigh muscles must be rebuilt in a very targeted manner after surgery—the first few weeks are crucial here. Pre-existing sarcopenia further complicates this process.
• Patient satisfaction rate: About 80 to 85 percent after knee TEP, compared to over 90 percent after hip TEP. This is not a sign of inferior surgical technique, but rather a reflection of the anatomical complexity.

Realistically, this means that full weight-bearing capacity and maximum range of motion are not achieved until three to six months after knee replacement surgery. Those who understand this will assess their progress appropriately—and won’t be disappointed after three weeks that things aren’t yet “back to normal.”

The most important rule of knee rehab: bend, bend, bend. The first few weeks determine how far the knee will be able to bend later on. Those who practice consistently during this time will benefit for years to come.

For patients over 75—and especially those over 80—a structured preoperative geriatric assessment prior to knee TEP is standard practice in modern geriatric medicine:

• Frailty status: Clinical Frailty Scale. Essential for decision-making before any major surgery. More on frailty syndrome.
• Cognition: MMSE or MoCA. Pre-existing dementia in older adults significantly complicates rehabilitation—postoperative exercises require understanding and cooperation.
• Mobility: Gait analysis, Timed Up and Go, Tinetti Test. The function of the other knee and the hips also determines the course of rehabilitation.
• Medication review: Particularly critical: anticoagulants, anti-inflammatory drugs (NSAIDs), and anticholinergic agents. Key terms: polypharmacy in older adults and deprescribing.
• Nutrition and social environment: Particularly important for total knee replacement (TKR), as recovery takes longer. Malnutrition in older adults significantly increases the risk of complications.

→ For a comprehensive assessment of surgical risk: Surgical Risk in Older Adults.

→ For frailty assessment: Frailty syndrome.

Studies on knee TEP consistently show that patients who engage in structured exercise before surgery experience a faster return to mobility, less pain, and higher satisfaction. Core components of prehabilitation:

• Strengthening the thigh muscles (quadriceps, hamstrings)
• Range-of-motion exercises for the affected knee, to the best of one’s ability
• Endurance training for cardiovascular conditioning
• Training in postoperative exercises to ensure familiarity with the routine
• Optimization of medication, particularly the reduction of potentially problematic drugs
• Weight loss, if possible—every kilogram lost reduces the load on the knee joint by a factor of four when walking

Total knee replacement (TKR) typically takes 60 to 120 minutes. It is usually performed under regional anesthesia (spinal anesthesia) with light sedation—this reduces postoperative complications compared to general anesthesia, particularly the risk of delirium in older adults.

Postoperative care follows modern fast-track protocols:

• Mobilization on the day of surgery or by Day 1 at the latest
• Multimodal pain management with a minimal opioid dose
• Continuous passive motion (CPM)—now used in a targeted manner
• Early cold therapy and lymphatic drainage to reduce swelling
• Delirium screening and prevention
• Thrombosis prophylaxis for at least two weeks

→ For postoperative delirium prevention: Delirium in older adults.

Phase 1: Acute phase (Day 1 through discharge)

Goal: Safe mobilization with a walking aid, pain-adapted activity levels, and the start of range-of-motion exercises. Typical length of stay in the acute care facility: 5 to 10 days.

Phase 2: Inpatient follow-up rehabilitation (3 weeks)

Focus: Improving joint range of motion to at least 90 degrees, muscle strengthening, gait training, and pain-controlled increase in activity levels. Limited mobility during this phase is normal and will improve with consistent training.

Phase 3: Outpatient follow-up treatment (2 to 6 months)

Continuation of physical therapy, further training at home, and gradual restoration of full functionality. Final range of motion and functional capacity are usually achieved after three to six months.

→ When early geriatric rehabilitation is indicated: Early Geriatric Rehabilitation.

• Pain: Severe pain prevents patients from performing the necessary exercises. Consistent multimodal pain management is a prerequisite, not an optional extra.
• Swelling: Normal in the first few weeks; can be significantly reduced with consistent elevation, cooling, and lymphatic drainage.
• Arthrofibrosis: Excessive scar tissue formation leading to restricted movement. Consistent early mobility is the most important preventive measure.
• Depression: The demanding rehabilitation process takes a psychological toll. Depression in older adults during the second postoperative week is common and recognizable—it is not inevitable.
• Cognitive impairment: In cases of pre-existing dementia in older adults or postoperative delirium, cooperation with the exercises becomes more difficult. Structured, simplified, and repeated instruction is particularly important here.

Key points to know:

• Infection: 1 to 2 percent. Oral hygiene, a preoperative dental checkup, and proper postoperative wound care reduce the risk.
• Thrombosis and pulmonary embolism: Rare with adequate prophylaxis.
• Arthrofibrosis: Limited range of motion that may require treatment through mobilization under anesthesia or, in rare cases, repeat surgery.
• Loosening of the prosthesis: Rare in the first 10 years, more common thereafter.
• Persistent pain: In 10 to 20 percent of patients, significant pain persists despite a technically sound prosthesis.

The long-term prognosis is very good: Over 90 percent of total knee replacements are still functional after 15 years. The revision rate is about 1 percent per year. In older patients with age-related osteoporosis, the risk of fracture in the event of another fall should be taken into account.

For planned total knee replacements (TKR), the reasons for consultation are the same as for total hip replacements (THR). Specifically:

• Age over 75 with five or more long-term medications — key term: polypharmacy in older adults
• Pre-existing cognitive impairment, suspected dementia, or depression in older adults
• Signs of frailty such as muscle weakness, unintentional weight loss, and exhaustion
• Repeated falls in older adults or fear of falling
• Heart failure in older adults, COPD, or severe diabetes in older adults with complications
• Multimorbidity raising questions about treatment prioritization

Leading Medicine Guide features a wide range of specialized orthopedic surgeons for joint replacement. The combination of orthopedic expertise and geriatric care is the model of care that yields the best outcomes for older patients—and is increasingly recognized as a hallmark of quality care.

→ How a comprehensive geriatric assessment supports decision-making: Geriatric Assessment.