When hip and knee pain strike, many runners suspect it’s their iliotibial (IT) band. While this thick band of tissue is a common culprit for hip and knee pain, there may be another muscle at play: the sartorius muscle.

The sartorius is unique. Not only is it the longest muscle in the body, but it’s one of only two muscles that cross two joints (the hip and knee), Dr Christopher Hicks, a sports medicine physician tells Runner’s World. Therefore, the sartorius is highly active during most phases of your run stride, and thus may contribute to muscle pain and cramps.

To understand how the sartorius works, let’s pause for a quick anatomy lesson: The sartorius is a thin, strap-like muscle that starts at the front of the hip, crosses the front of the thigh (quadriceps), and attaches to the inside of the knee, creating a stretched-out “S” shape. It flexes both your hip and knee, rotates your hip outward, and helps stabilise your pelvis — three essential movements in running, Hicks says.

So why does the sartorius muscle often cause problems in runners? We break down what you need to know to run ache-free.

What causes sartorius muscle pain and cramps in runners?
The sartorius muscle isn’t a strong hip or knee flexor compared to the larger, more powerful muscles nearby, including the iliopsoas, rectus femoris (a quadriceps muscle), and hamstrings. “However, given the innate function of the sartorius muscle, it is highly active and can be overused,” Hicks says.

Pain at the front of the hip and along the quadriceps may indicate that tightness in larger hip flexor muscles is straining the sartorius. “Your sartorius is going to work harder if your hip flexors are tight,” Dr Lauren Simon, a sports medicine physician tells Runner’s World. When the other hip flexor muscles can’t lengthen enough to facilitate your running stride, your sartorius has to contribute more than it’s used to, leading to tightness and pain.

Overstriding is another common cause of sartorius pain. “The sartorius goes hip-to-knee, so if you overstride, you can yank on it, which can make it hurt,” Simon says. Sprinting too often can annoy the sartorius for the same reason, she adds.

What makes sartorius muscle pain and cramps stand out from other injuries?
For some, sartorius pain can be felt as a sore, burning sensation along the front inside portion of the knee. This may mean you’ve irritated the pes anserine bursa, which are small, fluid-filled sacs that cushion the tissues near the knee joint. The pes anserine bursa is located beneath the insertion point of the sartorius and two other muscles: the gracilis (a muscle of the inner thigh) and the semitendinosus (a hamstring muscle).

If these three muscles are tight, they put excess pressure on the bursa, affecting how well it can reduce friction when muscle and tendon glide over bone, per the International Sports Sciences Association (ISSA).

Some runners complain of cramping in the sartorius, though it may not be a muscle cramp in the traditional sense. “Typically, a true muscle cramp is a muscle that’s actively contracting in a painful way during exercise,” Professor  Jacqueline Palmer,  an assistant professor in physical therapy at the University of Minnesota Medical School tells Runner’s World. Muscle cramps often happen if you overexert for an extended period or in the heat.

When it comes to the sartorius, the cramping may feel more like painful tightness at any point along the muscle. “It feels like a hot rubber band when you’re running, and if you keep pushing through, you feel more of a crampy pain,” Simon says.

How can you treat sartorius muscle pain and cramps?
Addressing muscle tightness and strength imbalances are the first steps toward fixing sartorius muscle pain and cramps.

It can also help to visit a physiotherapist for feedback on your form. “Are you internally rotating your hips when you run? Are you overstriding? They can look at that kind of thing and help you fix your biomechanics,” Simon says. Simple tweaks can take some strain off your sartorius and resolve pain.

Here are a few ways you can treat sartorius muscle pain and cramps on your own.

Stretch the Hip Flexors
As mentioned earlier, the sartorius works closely with other muscles to flex the hips. Stretching all the hip flexors — including the sartorius — can relieve tightness, helping every muscle do its part.

“The sartorius is actually challenging to truly target and stretch because it crosses two joints, so you have to think about the positioning of both the hip and knee,” Palmer says. Luckily, most hip flexor stretches will hit the sartorius to some extent.

William Kelley, owner of Aries Physical Therapy, recommends doing the 90/90 hip stretch, which hits internal and external hip rotation, after every run when you’re warmed up, as it’s a static stretch. For a more straightforward hip stretch, you can also try a high lunge.

90/90 Stretch

How to do it:

1. Start seated. Place left shin on ground in front of torso and right shin to the side, with knee in line with hip, both knees bent 90 degrees.
2. Lean forward over left shin until there is a deep stretch in right hip and glutes.
3. Press left leg into ground to activate the hips and glutes. Hold for 20 seconds.
4. Repeat on opposite leg. Do 3 sets.

High Lunge

How to do it:

1. Stand with feet together, abdominals engaged, shoulders away from ears, hands by sides or in prayer pose in front of chest.
2. Take a big step back with left foot, landing on the ball of foot, and keeping leg straight.
3. While doing this, bend right knee so upper thigh is parallel to floor, shin perpendicular.
4. Point the front of both hips forward and squeeze legs toward each other before reaching arms overhead.
5. Hold for at least 30 seconds.
6. Repeat on the other side.

Strengthen Opposing and Supporting Muscle Groups

Tight hip flexors often signal weak hip extensors (muscles that straighten the hips). “One of the strategies that I often use with people with hip flexor overuse injuries is strengthening the glutes and hamstrings,” Palmer says. Incorporate exercises that target the glutes and hamstrings into a full-body strength routine three times per week, like the glute bridge and deadlift.

Glute Bridge

How to do it:

1. Lie face up, knees bent, and feet planted on the floor.
2. Drive through heels, contracting the glutes to lift hips up toward the ceiling. Body should form a straight line from shoulders to knees.
3. Lower hips down slowly.
4. Repeat. Do 12 reps.

Deadlift

How to do it:

1. Stand with feet hip-width apart, slight bend in knees. Hold a dumbbell in each hand down in front of thighs. Pull shoulders down and back.
2. Hinge at hips by sending glutes straight back. Keep back flat and core engaged.
3. Drive through feet to stand back up, extending hips.
4. Repeat. Do 12 reps.

One more thing: just because your sartorius is tight doesn’t mean it’s strong. To strengthen the sartorius itself, Palmer recommends the fire hydrant exercise.

Fire Hydrant

How to do it:

1. Get on all fours with wrists under shoulders and knees under hips.
2. Keep left knee on floor and lift right leg out to the side, knee bent 90 degrees. Lift as. high as possible without dropping opposite hip. Keep hips square to the floor.
3. Lower right knee back down.
4. Repeat. Do 3 sets of 6-10 reps.

How long does it take to feel results?
The timing of your recovery depends on the issue with your sartorius and how quickly you address it. Generally, the sooner you tackle your sartorius muscle pain, the less time it takes to recover.

If the pain and soreness stem from tightness, you may feel a change within one to four weeks, depending on how consistent you are with your rehab routine, Hicks says. Muscle strains typically take longer to heal — about four to six weeks to notice improvement.

Severe pain, swelling, loss of function, and popping or ripping sensations are good indicators to stop running and visit a sports physician for help.

READ MORE ON: glutes hip flexors knee-pain muscle pain sartorius muscle strength exercises stretching