Outside (Lateral) Knee Pain – Popliteus Tendinitis

| October 7, 2011

Anatomy of the Popliteus Muscle

of the knees.

Popliteus muscle of the Right leg. The Left leg mirrors this to form a type of W shape at the back

The popliteus is a thin, triangular muscle that helps form the bottom part of the popliteal fossa (one of 3 lymph glands we have).

It’s tendon, seen at the top of the muscle in the image to the right, works with the articular capsule of the knee joint, and lies between a fibrous capsule and a synovial membrane.

This tiny little muscle serves several important functions including:

  1. It assists in unlocking the knee on extension (when we straighten our knee)
  2. It works with the posteior cruciate ligament (PCL) to reduce the shin bone from gliding posteriorly in relation to the thigh bone
  3. It reinforces the posterolateral (behind and to the outside) joint capsule
  4. It reduces impingement of the lateral minsiscus (shock absorber)

The popliteus bursa is a fluid filled sac which helps prevent excessive friction, lies deep to the popliteus tendon.  Without this important structure, it would only increase the liklehood of tendinitis in the knee.

When standing with the legs straight, the popliteus acts to rotate the femur laterally 5 degrees on the top of the shin bone which unlocks the joint so that flexion can occur.  That is just a fancy way of saying that your poplitues is kind of like your front door key.  As the popliteus begins to contract, the shin bones (lower part) begin to rotate to the outside.  This motion allows the knee to bend which allows us to walk, run, skip or pretty much about anything.

The popliteus muscle plays a vital role in unlocking the knee joint and allowing normal Gait mechanics to work. Image taken from Google

After all, we are bipedal (move on 2 limbs).

During walking, when the foot is in the air and off the ground and the knee is flexed, the popliteus can roate the shin bones to the inside underneath the femoral condyles (ends of the thigh bones), therefore providing a very important role in locomotion.

Acute tears  can occur in association with injuies to the posteior cruciate ligament (PCL),  and lateral ligaments of the knee.  The popliteus may also become strained in patients with instability at the back, or the outside of the knee.

Tendinitis is common in runners, especially if they increase their mileage, which is common leading up to events such as 10k’s, half and full marathons.  It is also associated with downhill running due to the stress it must deal with with the downward forces.


Pain will be usually be felt at the outside of the knee when running, and especially when downhill running.  You might notice some tenderness on the outside of the thigh.  A careful diagnosis is important at this stage as it can often be confused with Iliotibial Band Friction Syndrome (IBFS).

A useful test is completed when laying face down and bending your knees to 30 degrees.

The ITB connects the top of the hip to bellow the knee joint. It blends in with the tendons of Tensor Fascia Lattae, and the Glutes.

Start by working against resistance, and activating the hamstrings group.  Now rotate your toes outwards (external rotation), and apply more resistance to the leg while rotating the toes back inwards.

This can often reproduce the pain, and should be performed under the supervision of a physiotherapist, osteopath, or sports rehab specialist.


As with a lot of injuries, the early stages of managment should see a decrease in activity levels, which should be appropriate to the severtiy of the injury.  If inflammation is present, it could be minimised through the use R.I.C.E.

Other modalities which should be considered include:

  • Minimise any pain and/or swelling through the use of NSAID’s, and PRICE techniques, respectively
  • Begin therapeutic exercises to strengthen any weaknesses in the lower kenetic chain
  • Electrotherapy techniques have been proven to be useful in reducing pain and swelling.  Laser treatment, Ultrasound, TENS, and Interferential stimulation have all been shown to be effective.


The rehabilitation process is more likely to be successful if the following list adhered to:

  1. Any tight muscles or other soft tissue structures which are restrictive should be lengthened through static stretching.  Typically, this would include the muscles surrounding the knee such as the hamstrings, quadriceps and gastrocnemius (calves)
  2. An eccentric strengthening programme (strengthening while the muscle is lengthening) should begin for the muscles which attach to the tendon.  This will improve the tensile stretngth of the tendon and help prevent future injuries.
  3. Muscle length, and strength tests could be carried out to make sure there are no imbalances, and therefore compensations within the muscles that surround the knee.
  4. Massage techniques such as cross-frictions, are common in order to break down the adhessions (knots) in the muscle, as well as increasing length and helping to reduce a reoccurance of the injury.
  5. It is advisable to provide some form of support to the tendon during the healing stage; particularly as the rehabilitation becomes more dynamic in nature.  This is often accomplished through taping and/or bracing the knee.
  6. Any problems that begin at the feet, such as pronation, should be corrected through the use of orthosis.  The footware that the person is wearing, particularly when they run, should be anaylysed.  If their shoes are not providing sufficient support, then the purchase of new shoes should be advised.
  7. Any faulty movement patterns which may be aiding to the tendinitis, should be established and corrected with help from a physiotherapist, osteopath, sports rehab specialist.

Lying Hip Extensions, sometimes called bridges, are a great way to help strengthen the hamstrings. Image taken from Google

The emphaisis during the initial stages is often on the conditioning of the tibial rotators and the hamstrings , through the use of therabands, or other hamstring exercises such as lying hip extensions (bridges) or machine leg curls.

If possible, you could use swissball leg curls which would be better and more appropriate to the demands of real

The Swiss Ball Leg Curl is a more advanced exercise than the Lying Hip Extension shown to the right. This should only be performed once you have the strength to perform the exercise with good technique

life (Multi-planar movements).  Fixed machines, such as machine leg curls work in one plan of motion, and are useful in the initial stages of injury or for absolute beginners.

As you can see, this tiny little muscle at the back of your knee, which you probably didn’t even know existed plays a massive part of how we move.  Besides it has a really cool name. Well, I like it anyway.

Until the next time,

Keep Your Knees Pain Free




Category: Knee Injury Rehabilitation

Comments (2)

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  1. That’s a really good post

  2. Kerry says:

    Hey, great article. I subscribed! My popliteus blew up on me after half marathon last weeken and wondering a couple of things. Race was all in one lane and my injury is on the downhill side. (O fncourseIs that a factor? And then the obvious question, why wasn’t it a factor for everyone?

    In the weeks before the race I did some plyometric jumping. Was that a bad idea?