Pop ... what? Meet the popliteus; a behind the scenes player that could be the biggest cause of your knee pain. One of the most common complaints amongst a wide demographic is knee pain. The causes can be as broad as the presentations. From patello-femoral (aka runner's knee), Iliiotibial Band Syndrome, Osgood Schlatter disease, and numerous additional ailments, many a knee pain can often be remedied with soft tissue treatments, corrective exercise prescription, and proper movement pattern re-education if the therapist knows where to begin.

The Whole Picture

Before diving into the treatment side of things, it's important to gain a wholistic picture of how the client moves as well as a static postural screen. Both of these tools can lead to a more successful treatment plan based on real observation of the client in motion and static posturing. At the very least, I recommend Gray Cook's Functional Movement Screen (FMS) as well as his Selective Functional Movement Assessment (SFMA) course.

The knee joint is the largest and most complex joint in the human body. It's also one of the most easily injured. Located in between the ankle joint, the hip joint, and all the muscles that contribute to locomotion, the knee is subject to a number of mechanical forces and factors. While most of us are extremely familiar with the quadriceps, hamstrings, and calf musculature, there is one particularly small muscle that plays a huge role in knee stabilization and it resides behind the scenes. Literally.

The popliteus can be found on the posterior leg and runs from the lateral side of the femur to the medial side of the tibia. It sits behind the knee deep to the superior calf and distal hamstring musculature. It inserts onto the medial, posterior tibial condyle and originates on the lateral femoral condyle on the superior aspect. When treating this area, be mindful of pressure and length of time spent there.

The Importance of Proper Mechanics

When it comes to gait pattern, this little muscle is critical in stabilization and proper mechanics. A tight or weak popliteus can wreak havoc not only on the knee but also in foot and hip function. The popliteus has three basic motions that have critical impact on gait pattern:

• Knee flexion
• Lateral rotation of the femur
• Medial rotation of the tibia/fibia

It contributes to knee flexion by initiating the motion and unlocking the knee from full extension. If the popliteus is tight or shortened, it has an inhibitory effect on leg extension thus an inability to fully straighten the leg.

When the foot is planted, such as in a walking or running gate, the popliteus laterally rotates the femur at the juncture of the tibia/fibia. During the transition phase of a gate pattern (foot is in the air) the lower leg is medially rotated under the femur readying for the next foot strike. A shortened popliteus in this case would cause excessive pronation and an improper foot placement in landing.

Gravitational Forces

In addition, the popliteus is extremely important when downhill running or walking. In conjunction with the posterior cruciate ligament, it assists decelerating the femur from sliding forward on the tibia due to gravitational forces. Given its deep location and often overlooked contributing role in gait pattern, it isn't typically included in standard treatment approaches to knee pain. However, it should be pretty clear at this point that ignoring this small, discrete player is a bad idea.

Now before you go digging around behind your clients knee like you're looking for the newest prize in the cracker jack box (totally just aged myself with that one), be precise about the placement of your fingers. There are nerves and blood vessels in the popliteal fossa that can become compressed or injured if too much pressure is applied.

It's also vital to determine if the popliteus is where you need to be spending your time. That's when a solid understanding of how to conduct movement assessment is essential as well as some basic detective work. If you already know that your client is an overpronator, that's a decent clue. Take a look at their running shoes or the shoes they wear everyday if you can't quite tell. Looking at the wear patterns on the sole of a shoe can tell you a lot about how someone spends time in their feet.

Locating the Source of Pain

If they're complaining of pain on the medial and/or front of the knee especially when they run, walk up stairs, or downhill, those are also signs that palpating the popliteal fossa is a good idea.

So how do you get your hands on it to treat it? Glad you asked. One of the easiest ways to access this muscle is to have your client lie prone with the leg being treated passively flexed and supported. It can also be accomplished with the client lying supine with the leg passively flexed and their foot on the table. From the lateral side:

1. Locate the biceps femoris tendon and gastroc/soleus musculature. This should place you right at the knee crease.
2. Gently hook your fingers behind the biceps femoris tendon.
3. Head medially toward the patella on the lateral condyle.
4. Palpate the tendonous insertion and note any discomfort or tissue properties that infer dysfunction.

From the medial side:

1. Find semi-tendonosus tendon going to the pes anserinus attaching to the tibia.
2. Gently move the gastroc/soleus out of the way.
3. Place your fingers posteriorly to land on the belly of the popliteus.

If your client has a history of chronic knee pain or pain that is worsening, the popliteus will likely be very tender. Apply the appropriate soft tissue techniques based on your findings and re-assess your client's perception of pain when performing a simple walking pattern, squatting, running, or any other motion that had previously caused pain.

Subsequent treatment sessions that include manual therapy as well as movement re-education may be in order depending on the clinical presentations. It's important to recognize that just as the popliteus can be the causation for knee pain, it can also create painful symptoms at the ankle and hip due to it's influence on gait.

Considering the Other Mechanics

In addition, the popliteus itself can become painful much like any other tendonosis. If the lateral hamstrings are stronger than the medial hamstrings, this will cause weakness in the popliteus and could lead to its injury or injury of the knee or both. Another contributing factor to stress on this muscle is overpronation at the foot. This often presents as medial knee pain and is confused with meniscus issues.

Assessing and treating knee pain should be an all encompassing and broad view of all potentially contributing factors. Sometimes taking a 10,000 foot view can serve as a faster way to determine the direction of treatment.

As always, avoid diagnosing and refer to the appropriate medical provider for anything not within your scope of practice. The next time you have a client complain of knee pain, let this little behind the scenes muscle "pop" into your clinical lens of speculation.