“I tried that for two years,” he says. But limiting himself just didn’t feel right. So he got another doctor and tried a new strategy. “I started exercising and doing the things a person who wants an active lifestyle should do,” he says. 

A former kayaking coach and karate instructor, he began focusing on low-impact resistance exercises for his legs so that his muscles could become strong enough to absorb the stress of activities like walking and hiking, rather than letting that pressure fall on his knee joints. In particular, he zeroed in on his hamstrings, quads, glutes, and calves.

And it worked. Despite his cartilage only being “as thick as a credit card,” as he puts it, he built up enough strength to support his knees through a hike across the entire state of South Carolina at age 75. That may seem pretty ambitious, but King, now 81 and a certified personal trainer working at Planet Fitness, says that these days, “my knees don’t give me any problems at all.”

How exercise can help arthritis symptoms

Experts back up King’s approach. “Exercise helps to maintain mobility and can help with decreasing further joint stiffening,” family physician Tamika Henry, MD, founder of Unlimited Health Institute, once told Well+Good about working out with arthritis. “Exercise also increases blood flow to the area, which can increase muscle strength and has been associated with a decrease in pain.” In particular, research¹ shows resistance training can be especially beneficial, improving joint function, pain, stiffness, and strength.

King’s top exercises for arthritic knees

So what were the exercises that helped King get strong enough to hike hundreds of miles on arthritic knees? These were the five he says he focused on most:

Leg extensions

This exercise zeroes in on the quadriceps on the top of the thighs. This is helpful because when the quads are weak, the patellar tendon at the base of the kneecap “will have a hard time managing the loads of activity,” physical therapist Joseph Rayner IV, DPT, previously told Well+Good about exercising for knee pain.

The most common way to do this exercise is on a dedicated leg extension machine.

1. Sit on the machine with your shins below the pad. Select a weight that’s just heavy enough for about 10 reps, with the last one or two reps feeling challenging to complete.
2. Slowly straighten your legs (but don’t lock your knees).
3. Gradually bring them back to the starting position without letting the weight drop.

If you don’t have access to a leg extension machine, you can find similar benefits at home by putting on ankle weights, or strapping a looped resistance band to the bottom of a chair or couch and sitting down, then extending one knee at a time against that resistance.

Hamstring curls

Many of us have tight, weak hamstrings from sitting so much. And when these muscles aren’t strong enough, other ones overcompensate, leading to imbalances that could strain our knees. Hamstring curls can help prevent this.

There are dedicated hamstring curl machines at the gym you can use:

1. Sitting on the machine, place your ankles on top of the pad. Select a weight that’s just heavy enough for about 10 reps with the last one or two reps feeling challenging to complete.
2. Slowly bend at the knee, bringing your feet toward your butt.
3. Gradually return to the starting position without letting the weight drop.

If you don’t have access to a machine, you can do standing hamstring curls using just your body weight, slowly bringing one heel at a time toward your butt. Or you can sit down, tie a looped resistance band to a point in front of you, then do seated hamstring curls one foot at a time.

Leg presses

A leg press will work on both your quads and hamstrings, and also get your glutes involved. And as Steve Stonehouse, CPT, vice president of programming for Stride and Body Fit Training, once told Well+Good, glute imbalances are not only super common, but they can lead to pain all the way down the kinetic chain of your legs—including the knees.

The traditional way to do these is to use a leg press machine.

1. Start with feet flat on the press, shoulder-width apart; you should have your knees bent at 90 degrees to begin.
2. Once you’ve selected an appropriate weight to do 10 reps with the last one or two being challenging to complete, push through your heels to straighten your legs (but don’t lock the knees).
3. Slowly bend the knees to bring your body back toward the press without letting the weight drop.

If you don’t have access to a machine, this is another instance where resistance bands can come in handy: Lie on your back, feet in the air with the band wrapped around them (and holding the other end tight in your hands), then straighten and bend your legs against the band’s resistance.

Squats

Similar to a leg press, the classic squat will work your quads, hamstrings, and glutes, and can be easily done with no equipment at all.

Standing with your feet hip-width apart, bend your knees to bring your butt back and then down (as though you’re about to sit in a chair), then straighten back up.

To increase the challenge, you can try squat variations like the goblet squat or front squat, both of which add weight.

Calf raises

“Calves are one of the most under-trained muscles in your body,” certified personal trainer Lindsey Lauten once told Well+Good. “If you’ve ever felt knee pain after doing a few burpees or running on a treadmill, weak calves could be behind it.” She says the solution is adding calf raises to your weekly lineup: “Calf raises are a simple, but super effective and beneficial, exercise.”

Here’s how to do them:

1. Stand tall, with legs hip-width apart and feet flat on the ground.
2. Push through the balls of your feet to bring your heels off the ground.
3. Lower back down slowly and with control.

To increase the challenge, you can try doing one leg at a time (grabbing onto something stable like the wall or countertop for balance), or holding weights while you complete the move.

King’s takeaway at age 81

In addition to training Planet Fitness members, King continues to work out regularly on his own, lifting weights or working with TRX straps four days a week, and getting in cardio at least once a week. And he still does a lot of kayaking, which he says gives him a total-body workout.

His motto? “We can’t give up our active lifestyle,” King says. “It’s too important to be active at whatever level you can.”