The Sartorius: insertional tendinitis and medial knee pain?

We all see folks with medial knee pain, many times women, with the pain located just below the medial tibial plateau. It often results from running, but sometimes with jumping sports like basketball as well. It has been our experience that these people are often diagnosed with an MCL type injury, but when you examine them further, they do not really fit the bill. All the ligaments are stable and there is no tenderness at the joint line. The is often tenderness at the pes anserine, but who is driving the bus here?

image source: https://commons.wikimedia.org/wiki/File:Muscles_and_tendons_of_the_legs_and_feet;_écorch_́figur_Wellcome_V0008276.jpg

The sartorius originates from the anterior compartment of the thigh. During an ideal gait cycle, the sartorius fires from toe off through nearly terminal swing (1)

We remember that the abdominals should initiate thigh flexion with the iliopsoas, rectus femoris, tensor fascia lata and sartorius perpetuating the motion. Sometimes, when the abdominals are insufficient, we will substitute other thigh flexors, often the psoas and/or rectus femoris, but sometimes sartorius, especially in people with excessive midfoot pronation. Think about all of the medial rotation occurring at the knee during excessive midfoot pronation and when overpronation occurs, the extra compensatory external rotation that must occur to try and bring the knee back into the sagittal plane. The sartorius is positioned perfectly for this function, along with the semitendinosus which assists and external rotation in closed chain. This is why it is often implicated as the culprit in many cases of pes anserine bursitis (or as we like to say “sartorius insertional tendinitis” (2-3)

Some other things you may find interesting is that it is utilized more in crossing or cutting maneuvers while changing directions while running (4). This makes sense, given its anatomical course and origin/insertion. It can often be overlooked in adductor strains. It can also be avulsed during sprints, particularly in adolescents (5) and because of the course of the lateral femoral cutaneus nerve beneath it, can be the cause of meralgia paresthetica (6). It is proprotionally smaller in females (along with the gracilis and short head of the biceps femoris) (7). And during vertical jumping, is considered an internal rotator, along with the semimembranosis, semitendinosis, gracilis, and popliteus (8).

The sartorius is superficial in the anterior thigh, just under the skin, running from the ASIS, coursing lateral to medial and inserting at the pes anserine at its most superior aspect, just overlying the gracilis. Since it is an external rotator, knee flexor and assists in thigh abduction, you can easliy locate it by placing the patient in a "figure 4" position and having them resist as you pull downward on the leg. Be careful if you are needling this muscle because of the subsartorial canal (ie Hunters canal) lying just beneath it in the middle 1/3 of the thigh, from the apex of the femoral triangle to the adductor hiatus in the adductor magnus. It houses the femoral artery and vein, as well as the saphenous nerve and nerve to the vastus medialis.

1. Michaud T: in Human Locomotion: The Conservative Management of Gait-Related Disorders 2011

2. Imani F, Rahimzadeh P, Abolhasan Gharehdag F, Faiz SH. Sonoanatomic variation of pes anserine bursa. Korean J Pain. 2013;26(3):249-54. 

3. Gupta, Aman & Saraf, Abhinesh & Yadav, Chandrajeet. (2013). ISSN 2347-954X (Print) High-Resolution Ultrasonography in PesAnserinus Bursitis: Case Report and Literature Review. 1. 753-757. 

4. Rand MK, Ohtsuki T. EMG analysis of lower limb muscles in humans during quick change in running directions. Gait Posture. 2000 Oct;12(2):169-83.

5. Manning CJ, Singhai S, Marshall P. Synchronised sartorius avulsions in adolescent sprinter. BMJ Case Rep. 2016 Jul 13;2016.

6. Hsu CY, Wu CM, Lin SW, Cheng KL. Anterior superior iliac spine avulsion fracture presenting as meralgia paraesthetica in an adolescent sprinter. J Rehabil Med. 2014 Feb;46(2):188-90. doi: 10.2340/16501977-1247.

7. Behan FP, Maden-Wilkinson TM, Pain MTG, Folland JP. Sex differences in muscle morphology of the knee flexors and knee extensors. PLoS One. 2018 Jan 23;13(1):e0190903.

8. Cleather DJ. An important role of the biarticular hamstrings is to exert internal/external rotation moments on the tibia during vertical jumping. J Theor Biol. 2018 Oct 14;455:101-108

Yes, we are all twisted; Part 3

In the last 2 posts we discussed the differences between torsions and versions, as well as talar version and torsion, 1 of the 3 major versional events that occur during normal development (missed out? Click here and here to re read them).

In this post we discuss tibial versions and torsions.

The tibia and femur are more prone to torsional defects, as they are longer lamellar (layered) bones as opposed to the cancellous bone that makes up the talus. These often present as an “in toeing” or “out toeing” of the foot with respect to the leg; changing the progression angle of gait (click here for more on progression angles).

Tibial versions and torsions can be measured by the “thigh foot angle” (the angulation of the foot to the thigh with the leg bent 90 degrees: above right) or the “transmalleolar angle” (the angle that a line drawn between the medial and lateral malleoli of the ankle makes with the tibial plateau: above left). 

At a gestational age of 5 months, the fetus has approximately 20° of internal tibial torsion. As the fetus matures, The tibia then rotates externally, and most newborns have an average of 0- 4° of internal tibial torsion. At birth, there should be little to no torsion of the tibia; the proximal and distal portions of the bone have little angular difference (see above: top). Postnatally, the tibia should twist outward (externally) a total of 15 degrees until adult values are reached between ages 8 and 10 years of 23° of external tibial torsion (range, 0° to 40°). 

Sometimes the rotation at birth is excessive. This is called a torsion. Five in 10,000 children born will have rotational deformities of the legs. The most common cause is position and pressure (on the lower legs) in the uterus (an unstretched uterus in a first pregnancy causes greater pressuremaking the first-born child more prone to rotational deformities. Growth of the  unborn child accelerates during the last 10 weeks and the compression from the uterus thus increases. As you would guess, premature infants have less rotational deformities than full-term infants. This is probably due to decreased pressure in the uterus. Twins take up more space in the uterus and are more likely to have rotational deformities. 

Of interesting note, there is a 2:1 preponderance of left sided deformities believed to be due to most babies being carried on their backs on the left side of the mother in utero, causing the left leg to overlie the right in an externally rotated and abducted position.

Normal ranges of versions and torsions are highly variable (see chart above: right). Ranges less than the values are considered internal tibial torsion and greater external tibial torsion.

Internal tibial torsion (ITT) usually corrects 1 to 2 years after physiological bowing of the tibia (ie tibial varum) resolves. External tibial torsion (TT) is less common in infancy than ITT but is more likely to persist in later childhood and NOT resolve with growth because the natural progression of development is toward increasing external torsion.

Males and females seem to be affected equally, with about two thirds of patients are affected bilaterally and the differences in normal tibial version values are often expected to be cultural, lifestyle and posture related.

 The ability to compensate for a tibial torsion depends on the amount of inversion and eversion present in the foot and on the amount of rotation possible at the hip. Internal torsion causes the foot to adduct, and the patient tries to compensate by everting the foot and/or by externally rotating at the hip. Similarly, persons with external tibial torsion invert at the foot and internally rotate at the hip. Both can decrease walking agility and speed if severe. With an external tibial torsion deformity of 30 degrees , the capacities of soleus, posterior gluteus medius, and gluteus maximus to extend both the hip and knee were all reduced by over 10%.

Well, that was probably more than you wanted to know about tibial torsions, and we could go on for many more pages and perhaps cure any insomnia you may have. Take a while to digest this, as it is important to gait, shoe selection, and rehabilitation. Torsions are an acquired taste and we hope we have whetted your appetite! Tomorrow we talk about compensations!

Ivo and Shawn; two twisted guys!

All material copyright 2013 The Gait Guys/ The Homunculus Group. All rights reserved.  Ask before you lift our stuff, Lee is watching……