Knee Pain and the pes anserinus tendons

Ross Hauser, MDRoss Hauser, MD

A common cause of knee pain is not ligament injury. (We realize that this is shocking, since we have been explaining in past newsletters that ligaments are normally the cause of chronic pain.) The most common cause of chronic knee pain (see Prolotherapy research paper) is weakness in the pes anserinus tendons.

Below the knee cap, on the inside of the knee, are the attachments of three tendons: semimembranous, semitendinosus, and gracilis. Together, these tendons create the pes anserinus area.

I remember coming across a classic pes anserinus case while on rounds as a new doctor in the hospital. A 35-year-old nurse, told me her rheumatologist diagnosed her with arthritis and had prescribed anti-inflammatory medication. When he examined her knee, he found that she had full range of motion.

Full range of motion of the knee makes it unlikely arthritis is the cause of knee pain. On further examination, I was able to elicit a positive “jump-off-her-chair sign” when he pressed his thumb into the pes anserinus area showing pes anserinus tendonitis.

When I give a presentation, I enjoy asking the audience, “What is the number one reason for severe knee pain in the elderly?” The overwhelming response is arthritis, which is incorrect. The number one reason for severe knee pain in the elderly is pes anserinus tendonitis which, when left untreated, may contribute to developing arthritis. Even in cases of significant arthritis, crippling knee pain is most often due to pes anserinus tendonitis or bursitis. This condition is easily treated with Prolotherapy.

The pes anserinus tendon, also known as the inside hamstring muscles, flex the knee and stabilize the inside of the knee. Most of us have very, very, very weak hamstring muscles that are very short because we sit for a large portion of our day. Many patients, especially those with fallen arches are prone to strains in these muscles. The tibia tends to rotate outward to compensate for the fallen arch. This outward rotation of the tibia places additional stress on the pes anserinus tendons. Eventually, these tendons become lax and are no longer able to control the tibial movement, adding to the chronic knee pain. An arch support may be prescribed to reestablish the arch.

Prolotherapy injections along the arch of the foot will also prove beneficial. Prolotherapy injections into the pes anserinus attachments to the bone strengthen the tendon attachments and resolve the chronic knee pain.