Quadriceps-Strengthening Exercises That Minimize Knee Joint Stress

If you have knee pain due to patellofemoral stress syndrome (PFSS), then you may benefit from the skilled services of a physical therapist to help you manage your pain and return to optimal function. Your PT can assess your condition to determine the cause of your problem and can prescribe the right treatment for you.

Patellofemoral stress syndrome can be caused by many different factors. Weakness in your hips may place increased stress on your knee or knees. Pronated feet may cause your legs to rotate inward abnormally and place stress on your knee. Weakness in your quadriceps muscles may also be a cause of PFSS.

If your physical therapist determines that quadriceps weakness may be a factor in your PFSS, he or she will likely prescribe strengthening exercises to help improve the way your knee functions. Your quadriceps muscles help straighten your knees, and they are important in controlling the position of your kneecap while walking, running, and climbing stairs or rising from a chair.

Sometimes performing quadriceps strengthening exercises can place increased stress on your knee, and this may actually increase your pain and potentially worsen your condition. That can place you in a conundrum-you need to strengthening your quads, but in doing so you are increasing your knee pain and worsening your PFSS condition.

So are there exercises that can be done to strengthen your quadriceps while minimizing stress on your knees?

There are. It all depends on how you perform the exercises.

What the Evidence Shows

A study in the Journal of Orthopedic and Sports Physical Therapy examined the effect of different quad strengthening exercises on patellofemoral joint strain. The researchers measured knee pressure in 10 healthy subjects as they performed squatting and knee extension exercises.

During the squatting exercise, the researchers found that stress was minimal while squatting in a very specific range of motion (ROM). From 0 to 45 degrees of knee flexion (90 degrees is when your knee is bent at a right angle, as when sitting in a chair), stress through your kneecap is minimized during a squat. Performing squatting exercises past the 45-degree mark increased knee stress significantly.

While performing a seated leg extension, the researchers found that significantly decreased knee stress was measured in the 90 to 45 degree ROM. As subjects straightened their knee all the way, patellofemoral joint stress increased. The researchers also found that using variable resistance was less stressful when compared to using constant resistance for the leg extension exercise.

A Word of Caution

While this study shows that knee stress can be minimized by performing quadriceps exercises in a specific ROM, it only included healthy subjects. The results only measured patellofemoral joint strain and do not necessarily equate to subjects with PFSS. The evidence does provide a framework to use when deciding which quad strengthening exercises to perform and how to perform them to minimize knee stress.

How to Perform Quad Strengthening Exercises While Minimizing Knee Strain

Two specific exercises for quadriceps strengthening are the squat exercise and the seated leg extension exercise. Both of these help to engage your quadriceps, but they may also compress your kneecap and increase your pain. By modifying these exercises, you can help decrease stress and strain through your knees and strengthen your quadriceps while minimizing knee pain.

To perform the squat exercise safely, stand with your feet shoulder-width apart hold your arms in front of you. Slowly allow your knees to bend, but be sure to stop bending when your knees are at a 45-degree angle. Hold this position for a few seconds, and then slowly return to the starting position. Perform 10 to 15 repetitions of this exercise and be sure to limit how far you squat. Remember to stop when your knees are bent 45 degrees.​

To perform the knee extension exercise, sit in a chair with your knee bent 90 degrees. Straighten your knee out, but stop when it is about halfway up. Your knee should be bent 45 degrees.  Hold this position for a few seconds, and then slowly lower your leg down to the starting position. Remember to limit your knee ROM during the exercise. Repeat the exercise for 10 to 15 repetitions.

The leg extension exercise can be made more challenging by adding resistance. You can use a cuff weight around your ankle, or you can use a leg extension machine to perform the exercise.

Both the modified squat and leg extension exercises are designed to strengthen your quadriceps muscles while limiting the stress and strain to your knee joint. If either exercise causes pain, you should stop and check in with your physical therapist.

Before starting this, or any other, exercise program, check with your healthcare provider to make sure it is safe for you to do.

Since there are many causes of PFSS, make sure you work closely with your physical therapist to ensure that you are treating all of the factors that may be leading to your pain. Sometimes a knee brace is warranted or shoe orthotics are necessary to help your condition. There are even kinesiology taping techniques that can help control the position of your kneecap to treat PFSS.

Knee pain from patellofemoral stress syndrome can limit your ability to walk, run, and participate in normal recreational activities. Performing modified squatting and leg extension exercises can help strengthen the muscles that support your knees while minimizing stress to your joints. This can help to decrease your pain and get you up and moving quickly and safely.