The pes anserinus (or pes anserine tendon) is a combined tendon of three muscles (Gracilis, Sartorius & Semitendinosus). It is found on the inside of the knee joint and passes slightly anteriorly to attach to the inner, front (anteromedial) Tibia (shin bone).
Runners can experience pain in this area as a result of inflammation to either the tendon itself, or a bursa which sits between the tendon and the bone. A bursa is a small sack of fluid which is designed to reduce friction between soft tissues and the underlying bone. There arew numerous bursae around the knee, as well as the hip, shoulder and elbow joint for example.
The symptoms of pes anserinus tendonitis start with a gradually worsening pain on the inner knee, below the knee cap level. Initially the pain may ease as you warm up into your run, As the condition progresses, the pain will persist and often worsen.
It will be tender to touch the tendon and its insertion and some mild swelling or ‘puffiness’ may be visible. In worse cases the area may be warm to the touch. Away from running, pain is often aggravated by walking up stairs.
The symptoms don’t vary much between tendinitis and bursitis. The main difference is pain is often present at night with cases of bursitis.
What Causes Pes Anserinus Injuries?
Pes anserinus bursitis and tendinitis are overuse injuries which develop over time – rarely from one particular moment. If your pain occurred very suddenly, consider an MCL sprain. It may develop over the course of one long run, or maybe a few weeks. But the cause is overuse to the tendons – in whatever form. This results in small microtears within the tendon fibres which can become inflamed and painful. At this point, the body trys to heel itself and lays down scar tissue to repair the tears – but this is quite inflexible tissue which doesn’t function like normal tendon fibres. This causes stiffness in the tendon.
The tendon may become overused due to a change in your training – for example running more uphill or just increasing the intensity of your training program. Or a change in your footwear for example. New runners or those who haven’t had a professional gait analysis may be wearing unsuitable running shoes.
There are many other problems which could also contribute. For example, the hip muscles may be either too weak or too tight – or a combination! The hip muscles have a lot to answer for when it comes to running injuries! Problems in this area translate down into the knee joint as a rotation effect is placed on the Femur (thigh bone).
Treatment of Pes Anserinus Tendinitis / Bursitis
As with all running injuries the first step is to stop running and rest the knee. Ice should be applied for the first few days at regular intervals for 15 minutes at a time to ease pain and inflammation. Anti-inflammatory medications may also be advised by your Doctor.
If you choose to see a professional sports injury therapist they may use other treatments to help reduce the pain and inflammation, such as electrotherapies like ultrasound / laser.
They should assess you and your movement patterns / strength and flexibility from head to toe, This will help identify areas of weakness or tightness which may be contributing. They should also look at your running style, running shoes and training program.
Hip exercises which may be recommended include stretches for the hip flexors, groin muscles and rotators, as well as hip abductor strengthening such as clams and hip hitching exercises:
Return to Running
A return to running is not recommended until the tendon / bursa are free from pain on a daily basis and during other, non-weight bearing exercises such as cycling. Improvements in the hip strength should also be noted and any footwear and training errors corrected.
At this point, a graded return to running program can begin which should start with short duration jogging, possibly combined with walking intervals, for 10 minutes or so initially. Have a minimum of 2 days rest between runs to allow the muscles to recover and any recurrence of the pain to develop. If you experience no problems either during or after your first run, try the same again and gradually build in this way. If you feel the pain return at any point, rest and resume treatment.