Proof That Exercise Helps Arthritic Knees

If you have painful knee arthritis, exercising the knee may be the last thing on your To Do list. But studies like this one show that knee flexion and extension exercises do help. They improve strength and help your knee respond quickly to any change in position. The result can be less stiffness, faster walking speed, and a lower risk for falling. If you are a young athlete, that may not sound very important. But if you are an older adult, these benefits may grab your attention.

But exactly what kind of exercises should you do? Physical Therapists from the School and Graduate Institute of Physical Therapy in Taiwan are investigating this. They compared the effects of weight-bearing (WB) exercises (feet planted on the floor) with nonweight-bearing (NWB) exercises (feet off the floor) to see which one might increase knee function more. A third group of patients with knee osteoarthritis formed the control group. They did not do any exercises.

For eight weeks, patients in the weight-bearing group exercised in a sitting position with one foot on a platform that gave resistance to flexion and extension motions. Patients in the nonweight-bearing group were also sitting. But the foot was free to dangle. A cuff was attached around the ankle with an elastic band attached. The elastic provided resistance to knee flexion and extension without putting any weight through the foot.

Everyone completed three exercise sessions a week. They did four sets of six repetitions of knee flexion and extension. They were able to rest for one minute between each set of exercises. There was a ten-minute warm-up period on a stationary bike before the exercise program and a 10-minute cool down with cold packs to the knee afterwards. Both legs were exercised (one at a time) with a rest break of five minutes in between.

Before starting the program, each person was tested using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The WOMAC provides a scale of function. The researchers also measured walking speed, muscle torque, and knee reposition error. All measurements were taken before and after treatment for a comparison.

Walking speed was tested over different terrains including stairs, level (hard) surface, spongy surface, and in a figure-of-eight pattern. Muscle torque was a test of knee extensor and flexor muscle strength using a special device called a dynamometer. Strength was tested at three different speeds of motion. The reposition error test was done by placing the lower leg in a set position between zero and 90-degrees of knee flexion. After moving out of that position, the patient was instructed to return to the same position (as closely as possible). The difference between the target (desired) angle and the reposition (actual) angle was the knee reposition error.

You may wonder what difference it makes if your feet are on the floor (weight-bearing) or not (nonweight-bearing) while exercising. Here are a few things Physical Therapists consider when setting up an exercise program for patients with knee arthritis. With the feet in contact with the floor, a compressive force is generated that goes through the ankles, knees, and hips. The result may be an overload that increases pain, swelling and inflammation.

And one thing weight-bearing exercises provide that nonweight-bearing exercises don't is input or challenge to proprioceptive function. Proprioception is the (knee) joint's ability to recognize what position it is in and then respond to any changes (even small changes) in joint position. That's an extremely important function when you are walking on uneven ground, step on an object, or try to navigate a ramp or step off a curb.

The authors' efforts to see whether or not weight-bearing exercise improves function more than non-weight-bearing in patients with knee osteoarthritis produced some interesting results. First, patients in both exercise groups improved in function and strength. There was an 18 per cent improvement in strength and a 50 per cent decrease in disability. The control group showed no change over the eight-week period of time.

The weight-bearing group did have improved walking speed in the figure-eight pattern and on spongy surfaces. They also had improved position sense compared to the nonweight-bearing group. The authors suspect that it's the improved proprioception that made it possible to complete the more complex walking tasks faster.

They concluded that simple nonweight-bearing knee flexion/extension exercises are good and helpful in improving strength and overall function. This exercise regimen even helps improve stair-climbing skills. But appropriate weight-bearing exercises that don't overload the joint are even better. That's because the improved sense of joint position improves neuromuscular control of the knee on curved paths, over uneven floors, and when walking at a faster pace.

Although this study did not measure the effects of these exercise programs on falls, they suggest a future study may indeed find a difference in the risk of falling for older adults between those who exercise and those who don't. And there may be a measurable difference in falls between those who do weight-bearing versus nonweight-bearing exercises.

Mei-Hwa Jan, MS, PT, et al. Effects of Weight-Bearing Versus Nonweight-Bearing Exercise on Function, Walking Speed, and Position Sense in Participants with Knee Osteoarthritis: A Randomized Controlled Trial. In Archives of Physical Medicine and Rehabilitation. June 2009. Vol. 90. No. 6. Pp. 897-904.

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