A Quick Overview: Knee Pain, Knee Replacement, and Knee Rehab

Medically Reviewed by: Clint McCullough, ATC, OTC

What Causes Knee Pain?

Chronic knee pain is most often a result of a type of arthritis: osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis.  Knee arthritis is the degeneration or loss of cartilage in the knee joint. The cartilage is generally smooth and acts like a cushion between the ends of the thigh bone and shin bone. Over time, the cartilage becomes soft and wears away. This can make the bones rub against each other and cause pain and stiffness in the knee.

There are several non-operative treatments to chronic knee pain caused by arthritis such as weight loss, physical therapy, and injections (steroid and viscosupplementation). They may help with pain for a short period of time but they do not treat the underlying issue of arthritis. Unfortunately, the process of arthritis cannot be reversed and may require a total knee replacement to resolve the pain.

What is Total Knee Replacement?

Total knee replacement (knee arthroplasty) is an effective and safe procedure to relieve arthritic knee pain. During a total knee replacement, the articular surfaces of the lower thigh bone and upper shin bone are shaved down and replaced with mechanical implants. A plastic spacer is then placed between the metal surfaces to stabilize the knee and help the knee move smoothly.

Total knee replacement can also help correct leg deformities and help patients get back to their normal activities. Though approximately 800,000 knee replacements are performed in the US each year, total knee replacement is a big surgery and requires hard work from the patient to yield the best outcomes.

Why Would I Get a Knee Replacement?

The main reason to undergo a knee replacement is to relieve knee pain. Once knee pain is relieved, hopefully you can get back to your activities of daily living or even increase your pre-surgical activity level. One of the key factors in patient satisfaction and functional performance following knee replacement is early return of range of motion.

Achieving full knee extension as soon as possible following knee replacement is crucial for long term success. This may be challenging due to pain, swelling, and inhibition of the quadriceps, however, getting the knee completely straight will expedite your recovery.


A majority of gait function improvement can occur in the first 2-3 weeks following surgery and without full extension, patients may have an abnormal gait. During a normal gait cycle, the knee is fully extended during heel-strike and through most of the stance phase.

Helpful Tools After Knee Replacement

Zero Degree Knee

The Zero Degree Knee from MyComfortMD, is a simple positioning device that will help you get to full knee extension without the pain or effort of traditional exercises. The Zero Degree Knee works by elevating your heel and providing room behind your knee. This helps your muscles relax and lets gravity pull the leg into a fully extend position.

After surgery it may be difficult to engage your quadriceps muscles to extend your leg – the Zero Degree Knee helps you relax and lets gravity do the rest! Try it with a bag of ice over your knee at the same time to help you relax and reduce swelling!


Though early extension is crucial following knee replacement surgery, knee flexion is equally as important as you work back to full strength. Generally, knee flexion will be limited by swelling following surgery – this postoperative swelling is very normal and will improve with time. GAP-FLEX from MyComfortMD is a simple therapy system that provides a comfortable and less painful method to enhance patient recovery.

Like the Zero Degree Knee, GAP-FLEX utilizes gravity to increase knee flexion gently and comfortably. The multiple layers of foam protects your skin and lets you progress at your own pace from the comfort of your home! Patients who use GAP-FLEX require 90% less therapy time and significantly surpass their pre-surgery range of motion. See the proven results here!

Use the Zero Degree Knee and GAP-FLEX Together

Immediately following knee replacement surgery, it may be challenging to move around let alone get in the car and go to physical therapy. GAP-FLEX and the Zero Degree Knee bring physical therapy to the comfort of your own home!  These items work best when they are used together – GAP-FLEX for flexion exercises and the Zero Degree Knee for extension. Each of them utilizes the gentle force of gravity to do the work so you don’t have to!

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