What Causes Weakness in The Knee?

The knee is the largest joint in the body and acts as a hinge where the thighbone, shinbone, and kneecap bone meet. When a person experiences weakness in the knee, it can keep them from doing activities that they enjoy. It’s important to understand what can cause weakness in the knee so it can be addressed before it takes over your life.


Arthritis is inflammation in the joint that may worsen with age, causing weakness, pain and loss of range of motion. The most common types of arthritis that affect the knee are osteoarthritis and rheumatoid arthritis. Osteoarthritis, often referred to as degenerative arthritis, is the wear-and-tear that happens when cartilage in the knee deteriorates with use and aging. Rheumatoid arthritis is a chronic autoimmune disease that can affect a majority of joints in the body. Although it is the most debilitating form of arthritis, it can vary in severity and pain may come and go. While there are over 100 different types of arthritis that can affect the body, these two are the most common types that cause weakness or pain in the knee.


An injury of the knee can affect any of the surrounding ligaments, tendons, or bursae. It can also affect the bones, cartilage or ligaments that make up the joint itself. The most common injuries to the knee include ACL injury, patellar tendinitis, and fractures.

The anterior cruciate ligament, or ACL, is one of the four ligaments connecting the shinbone to the thighbone. An ACL injury would be a tear of ACL, which is most commonly seen in athletes that play sports where sudden directional changes are made, such as basketball or soccer.

Patellar tendonitis causes inflammation and irritation of one or more tendons in the knee when there is an injury to the patellar tendon. The patellar tendon connects the kneecap and the shinbone to allow you to run, jump, or kick. This injury is most commonly seen in runners, cyclists, or other sports where these movements may occur.

Fractures can occur to the kneecap during falls, car accidents or taking a wrong step on a weakened knee.

Mechanical Issues

Because the knee joint is a complex part of the body, mechanical issues can occur and cause pain or weakness in the knee. A dislocated kneecap happens when the bone covering your patella, or knee is shifted out of place. Typically, this shift moves the kneecap to the outside of the leg and can even stay there so that it can be seen. Another mechanical issue that may happen is hip or foot pain. If you have either of these, it’s likely that you change the way you walk to make up to the pain. While it may seem to help with your hip or foot issue, it puts more stress on your knee and can lead to a weakened knee joint.

Pain or weakness of the knee can be debilitating and frustrating to have to deal with. At Plano Orthopedic and Sports Medicine Center, we understand the emotions that come with the limitations of knee pain. Our highly-skilled, professional physicians can treat a variety of conditions both surgically and non-surgically. If you’re experiencing weakness in your knee, call us today to schedule an appointment.

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POSMC is a full-service medical facility specializing in the evaluation and treatment of orthopedic injuries. The practice is led by a group of 12 board-certified and fellowship-trained orthopedic surgeons and a physical medicine and rehabilitation physician. Contact us today!

Dr. Matthew C. Comley

Shoulder, Knee and Sports Medicine
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Dr. Adam Wright

Hip and Knee
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Dr. John E. McGarry

General Orthopedics, Shoulder, Knee and Sports Medicine
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Dr. John W. Barrington

Hip, Shoulder and Knee Replacement
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Dr. Randal L. Troop

Shoulder, Knee and Sports Medicine
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