Have you ever been standing at barbecue or party and felt you needed to sit down due to an aching pain behind your knee?
Have you ever been sitting at a movie theater and felt a sharp shooting pain behind your knee that distracted you from enjoying the movie?
Pain directly behind the knee is very common but can be misdiagnosed due to the amount of muscles, tendons, and tissues that reside there. Likely, you have searched the Google trying to find information on what could possibly be causing the pain behind your knee only to find scary and intimidating causes such as deep vein thrombosis (DVT) or posterior cruciate ligament (PCL) tear.
These are potential causes you want to pay attention to if you have had recent surgery, take blood thinners due to previous clotting, or had recent trauma to your knee. In these specific cases the course of action would be to call your doctor for a speedy appointment.
How about the majority of other cases though where the knee pain began without a know cause?
In this article we will explore the most common causes for pain in the back of the knee, but first lets peer into the anatomy of the back of the knee.
Anatomy: Posterior Knee
Anatomy of posterior knee Let’s start by looking at the large muscle anatomy of the posterior knee. In the image above you can visualize the two heads of the calf muscle (gastroc), and the multiple muscles that make up the hamstrings.
Some other features of the posterior knee include the gap or space behind the knee where there is a lack of soft tissue call the popliteal fossa. In the deeper muscle layer of the posterior knee you will find the popliteus and plantaris muscles.
Deep still you will find the posterior capsule of the knee joint. There are also important nerves that run along the back of the knee that can cause pain and make for a frustrating day.
Nerves behind the knee Now that we know the anatomy of the back of the knee we can explore the most common causes of posterior knee pain.
“I have this annoying pain that starts at my buttocks and goes down my leg!”
Sciatica is a very common cause of pain in the back of the knee and leg. Sciatica refers to pain along the path of the sciatic nerve due to irritation or compression of the nerve roots from the lower back or compression of the nerve from soft tissue in the buttocks.
Sciatica is most common in the 5th decade of life although can start as early as your 20’s and 30’s. In fact, it is estimated that you have up to a 40% chance of experiencing sciatica at some point in your life.
The pain you feel down your leg and at the back of your knee can be alleviated with physical therapy that focuses on decreasing activities that compress or load that lower back. This could take the shape of stretching, core strengthening, lifting education, and manual manipulation.
Sciatica is often present with prolonged standing and walking. Improving tissue flexibility at the hip flexors and strength of the gluteal muscles improves your ability to walk with less forces at the lower back. Additionally, unloading exercises such as “self-traction” can help with quick alleviation of symptoms and allow you to walk longer.
Distal Hamstring Strain
Hamstring strains are most common in the athletic population with sports that involve sprinting and quick bursts of speed.
During walking and running your hamstring muscles work to control the fast progression of your lower leg as it swings forward. When this force becomes to strong for the strength of the hamstrings the muscle will “pull” or stain causing small tears (or large ones if its severe). Straining your hamstring will create pain at the back of your thigh and back of your knee.
One of the best ways to recover from a hamstring strain (after the initial healing) is to perform eccentric strengthening drills. This specific form of hamstring strengthening will keep your muscle strong while it lengthens during running and sprinting. You can check out specific eccentric hamstring drills here.
Many people report having “tight hamstrings” despite stretching on a regular basis. This may be true if your job involves prolonged sitting with your knees bent which places your hamstrings in a shortened state.
If however, you have been diligently stretching and there is no change in your flexibility (and you feel a sharp feeling in the back of you knee when stretching) then your tight hamstrings may actually be a symptom of “neural tension”. In this case, it is tension in the sciatic nerve that is mimicking tightness in the hamstrings.
Proximal Calf Strain
Since your calf muscles cross the knee joint they can be another common cause of pain at the back of the knee.
Similar to hamstring strains, calf strains occur mostly in the active population but can also occur during daily activities as well. Sprinting, running, and jumping are common ways you can strain your calf since your calf is responsible for “pushing off” to propel your body forward.
Daily activities such as climbing stairs or hiking can create strain on the calf in the presence of a weak calf muscle or poor flexibility.
To alleviate pain at the back of the knee from a calf strain, stretching, ice, heat, and strengthening is recommended. Eccentric strengthening for the calf can also be performed to help with stairs and hiking.
Posterior Knee Pain: Meniscus Tear
It is likely that either you or someone you know has had a meniscus tear.
Approximately one million meniscus surgeries are performed each hear.
Your meniscus is a shock absorbing structure with two parts on the inside (medial) and outside (lateral) of your knee joint. Your meniscus is a specific type of tissue designed to withstand compressive and shear forces. When too much force or torque is present in a weight bearing movement the meniscus will tear. This can present as a “pop”, click, or snap and results in swelling, decreased range of motion, and pain in the knee.
The most common symptom is knee stiffness and pain during prolonged sitting and painful movement with squatting and stairs.
Since your meniscus wraps from the front of your knee to the back of your knee it can be a very common cause of back of the knee pain. Physical therapy which focuses on lower extremity alignment, hip strengthening, and manual therapy to restore range of motion can help alleviate the symptoms of a meniscus tear. Surgery is a very common treatment for meniscus tears given that the the majority of the meniscus is avascular and therefore will not heal by natural processes.
Back of Knee Pain: Baker’s Cyst
If you have had a recent injury, or chronic knee pain, and you feel there is a “ball behind your knee” you may have a Baker’s cyst.
A Baker’s cyst is a fluid filled pouch that forms at the back of the knee secondary to injury to the knee joint or soft tissue. The increase in fluid produced by the knee will create the cyst which takes up space behind the knee and limits your ability to bend the knee, squat, and stand.
A Baker’s cyst is commonly treated with conservative measures such as icing, wrapping, and physical therapy to help improve range of motion and function. Occasionally, the fluid in the back of the need can be drained by aspiration although it is common for the fluid to return due to the underlying pathology at the knee causing the swelling in the first place.
Although this list of common causes of pain at the back of the knee is not exhaustive, it does cover the most likely reasons for your knee pain. As stated above, if your knee pain is sudden and severe be sure to call your doctor. Your local physical therapist is a great resource to consult for questions about posterior knee pain and non-surgical ways to alleviate your pain.