Knee Pain: Safely Strengthening Your Thigh Muscles
Abstract
Quadriceps are the muscles on the front of your thigh that help you straighten your knee. When these muscles are not strong, you may feel pain under your kneecap. Quadriceps can be strengthened by performing squats and leg extensions. However, when you do not perform these exercises properly, you may also feel knee pain. Understanding the load and stress under the kneecap when you execute squats and leg extensions can help you perform these exercises better and with less pain while you strengthen your quadriceps. A study published in the May 2014 issue of JOSPT provides information intended to help physical therapists and their patients use these exercises to strengthen thigh muscles while minimizing the load under the kneecap. J Orthop Sports Phys Ther 2014;44(5):328. doi:10.2519/jospt.2014.0503
Quadriceps are the muscles on the front of your thigh that help you straighten your knee. When these muscles are not strong, you may feel pain under your kneecap. Quadriceps can be strengthened by performing squats and leg extensions. However, when you do not perform these exercises properly, you may also feel knee pain. Understanding the load and stress under the kneecap when you execute squats and leg extensions can help you perform these exercises better and with less pain while you strengthen your quadriceps. A study published in the May 2014 issue of JOSPT provides information intended to help physical therapists and their patients use these exercises to strengthen thigh muscles while minimizing the load under the kneecap.
This Perspectives article was written by a team of JOSPT's editorial board and staff, with Deydre S. Teyhen, PT, PhD, Editor, and Jeanne Robertson, Illustrator.
This JOSPT Perspectives for Patients is based on an article by Powers et al, titled “Patellofemoral Joint Stress During Weight-Bearing and Non-Weight-Bearing Quadriceps Exercises,” J Orthop Sports Phys Ther 2014;44(5):320-327. Epub 27 March 2014. doi:10.2519/jospt.2014.4936
New Insights
In this study, 10 healthy individuals performed both exercises. When doing the squat exercise, each participant began in a standing position with knees straight (0° of knee flexion), feet shoulder width apart, and toes facing forward. The individual then squatted until the knee joint was bent to 90°. This angle is similar to the angle of the knee when a person sits in a chair. The study participant then performed the leg extension exercise, sitting with good posture so that the knee and hip joints were both at 90°. The individual brought the leg up until it was parallel to the floor and the knee was straight (0° of knee flexion). The researchers used mathematical models to determine load and stress under the kneecap. They found that squatting halfway down (0°–45°) in the squat exercise and straightening the knee from 90° to 45° in the leg extension exercise produced the least amount of load under the kneecap.
Practical Advice
Limiting knee motion during strengthening exercises can help decrease the load under the kneecap. When starting a new exercise program for knee pain, your physical therapist may tell you to begin with “quarter squats” (0°–45°). Performing a quarter squat requires that you move just halfway between the standing and sitting positions. When doing leg extensions to strengthen your quadriceps, your therapist may tell you to start in the seated position and only straighten your leg halfway (90°–45°). Restricting motion in these exercises can help minimize the pain while doing them. As your quadriceps become stronger and you feel less pain under your kneecap, your therapist will increase the amount of motion that you can safely perform. Eventually, you should be able to do these exercises fully without pain. Your physical therapist can determine how you can safely strengthen your quadriceps to help treat your knee pain.
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