Rehab after a total knee replacement: what to expect and why physical therapy matters

Total knee replacement is one of the most common operations in the United States. The American Academy of Orthopaedic Surgeons says more than 700,000 are performed every year [1], and it is a successful surgery: more than 90% of modern knee replacements are still working well 15 years later [1].

The number keeps climbing. Among Medicare patients alone, researchers project that primary knee replacements will more than double by 2040 [2]:

• 2019 (actual)480,958
• 2040 (projected)1,222,988
• 2060 (projected)2,917,959

Source: Shichman et al., JBJS Open Access, 2023 [2]. Medicare data only, so not every US patient is included.

Still, a new knee is not automatically a pain-free knee. A systematic review found that about 1 in 5 people report unfavorable long-term pain after knee replacement in the best-quality studies (between 10% and 34% across studies) [3]. In a Canadian study of 1,703 knee replacements, 19% of patients were not satisfied with the result, and unmet expectations were one of the strongest predictors [4]. Good rehab and realistic expectations are a big part of getting the outcome you want.

What the physical therapy guideline recommends

In 2026 the American Physical Therapy Association updated its guideline for knee replacement rehab [5]. Its key points:

Recommendation	Strength
Start physical therapy, including getting up and moving, within 24 hours of surgery	Moderate
Progressive strength training for the operated leg	Strong
Motor function training, including balance and walking retraining	Strong
Supervised physical therapy after surgery	Moderate
An exercise program before surgery (prehab)	Moderate
Neuromuscular electrical stimulation (NMES) to the thigh muscle at least daily	Moderate
Ice for early pain, and ice plus keeping the leg raised for swelling	Moderate
A plan to increase physical activity step by step	Moderate
Do not use continuous passive motion (CPM) machines after a standard knee replacement	Strong
Do not routinely use braces or splints in the early weeks	Moderate

Source: Bove et al., APTA clinical practice guideline, revision 2026 [5]. Selection of the 20 recommendations.

A few of these deserve a closer look:

• The thigh muscle needs help waking up. In a trial of 66 patients, electrical stimulation of the quadriceps starting 48 hours after surgery improved strength, function and the ability to straighten the knee at 3.5 weeks, and the benefit was still there, though smaller, at one year [6].
• Steady progression matters more than brute intensity. A trial comparing high-intensity with low-intensity rehab found both improved strength and function, with no meaningful difference between them at 3 or 12 months [7]. The 2026 guideline now emphasizes progressive strength training rather than a specific intensity [5].
• An inpatient rehab stay did not add benefit. In an Australian trial, 10 days in an inpatient rehab unit did not improve walking ability at 26 weeks compared with a monitored home program [8]. The guideline notes that rehab may take place in an outpatient setting [5].

A typical recovery timeline

Every recovery is different, and your surgeon’s instructions come first. As a general guide from the American Academy of Orthopaedic Surgeons:

• Hours after surgery: most people can start moving the knee [1]
• 1 to 3 days: a typical hospital stay [9]
• First weeks: walking with a walker, crutches or cane, with some help at home; some pain with activity and at night is common [1]
• 3 to 6 weeks: most normal daily activities [1]
• About 4 to 6 weeks: most people resume driving, once they are off opioid pain medicine and their doctor agrees [1] [9]
• At least 2 months: keep doing the exercises your physical therapist prescribed [9]
• 3 to 6 months: mild to moderate swelling can last this long [9]

Most people end up able to almost fully straighten the knee and bend it to an average of about 115 degrees [1], enough for stairs, getting in and out of a car and most daily activities. Low-impact activities such as golf, cycling and pickleball are generally preferred over jumping, jogging and skiing [9].

Warning signs after surgery

Serious complications such as infection happen in fewer than 2% of patients [1], but it is important to recognize them early.

Call your surgeon right away if you notice [1]:

• Increasing pain, tenderness or new swelling in your calf, ankle or foot, or redness above or below the knee (possible blood clot)
• A persistent fever above 100°F, or chills
• Increasing redness, tenderness or swelling of the wound, or drainage from it
• Knee pain that keeps increasing both with activity and at rest

Call 911 if leg pain or swelling comes with sudden shortness of breath or chest pain, which can mean a blood clot has traveled to the lungs [1] [10].

The takeaway

• Knee replacement is common and usually lasts, but about 1 in 5 people still have pain afterward, so rehab and expectations matter.
• Guidelines recommend starting physical therapy within a day of surgery, progressive strength training, balance and walking practice, and supervised rehab.
• Prehab before surgery is recommended, and CPM machines are not.
• Most people return to daily activities in 3 to 6 weeks and keep improving for months.

You can start physical therapy in Utah without a referral, and prehab can begin before your surgery date. We coordinate with your surgeon so your plan matches their protocol.