Pictured above is the plantaris muscle. It helps bend your knee and raises your heel toward your knee. It attaches to the inside portion of the back of your thigh bone very near your knee and to the back of your heel bone. If this muscle locks up it will feel like a tight ball behind the knee. It is typically a symptom muscle instead of a source of your troubles. If you have plantaris issues you have OTHER bigger and stronger muscles that are not doing their job properly.

If this muscle regularly locks up on you, then you need to work on your quads EVERY DAY. Your quads extend (straighten) your knee, and the plantaris helps flex your knee. The quads are MUCH stronger than the plantaris (and all the other knee flexors, for that matter). In addition, your soleus muscle is probably locked up and your brain is firing the plantaris to help raise your heel more than it can handle. Be sure you check the soleus to relieve knots in it so your plantaris is no longer working harder than it should be.

The plantaris is displayed on the right leg. On the left leg the muscles are layered, showing how some of the muscles are covered by the others. All of the muscles are see-through so that you can appreciate the location and size of each muscle relative to the others.

Click here for a list of all the muscles.

Muscles that cross or attach to the hip or thigh bone (femur) and attach below the knee joint and DO NOT attach to the knee cap (patella)

  1. Sartorius
  2. Gracilis
  3. Biceps Femoris
  4. Semitendonosis
  5. Semimembranosis
  6. Gastrocnemius
  7. Popliteus
  8. Plantaris

Lower Leg
The following muscles attach across or below the knee.
Click the appropriate link for your interest.

Muscles that cross the knee

  1. Gastrocnemius
  2. Popliteus
  3. Plantaris

Muscles that pass or attach between the knee & ankle

  1. Gastrocnemius
  2. Popliteus
  3. Plantaris
  4. Soleus
  5. Peroneus Longus
  6. Peroneus Brevis
  7. Flexor Digitorum Longus
  8. Flexor Hallucis Longus
  9. Posterior Tibialis
  10. Anterior Tibialis
  11. Extensor Digitorum Longus
  12. Extensor Hallucis Longus

Good luck working out those tight knots.

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One thought on “Plantaris”

  1. Hi Jeff,
    I am having a problem with the inside tendon on the back of my left knee.
    I started rowing about two months ago on a Concept 2 rower. Things went well
    for about 2-3 weeks and then I started noticing little sharp pains like
    needles on the inside edge of my left knee. It felt like I was just not
    warmed up yet. So I decided to use my Rehband knee sleeves to keep them warm.
    The next couple of workouts were fine. Then on the third workout the pains
    came back and went across the top of my kneecap. The tendon started acting
    like it was going to cramp or like it was tangled up (?). After that, even
    walking sometimes felt like that. This pain is only in the first 2″-3″ from
    the bend of my knee, not like a “charley horse” or cramp. If I slow down my
    spm, I have been able to row some. A couple of weeks later while doing air
    squats I had a simular feeling. It was kind of like the tendon was tangled,
    out of place or something (I also use my knee sleeves for air squats). I have
    no problem at all with squats.

    Can you give me some advice?

    I’m 6’2″ and 250 lbs at 67 years old.

    Thank you,

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