The knee is a highly complex joint built up of multiple bones, muscles, tendons, and other tissues. And because there are so many (literal) moving parts, it’s extremely common for people to experience different kinds of pain in and around the knee joint.
Many individuals experience pain directly behind the knee, but they often receive incorrect diagnoses because of how many potential issues can occur.
If you’ve ever Googled “pain behind the knee,” you probably know what we mean — searching such a broad category of pain often pulls up severe and frightening results, like deep vein thrombosis or a posterior cruciate ligament tear.
And of course, while those results are possible concerns, they don’t represent the most common pathologies for pain behind the knee.
So, what are the most common problems, and what differentiates one from the other?
Anatomy of the Posterior Knee
Okay, before we get ahead of ourselves, let’s first review the anatomy for the back of the 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 (gastrocnemius) and the multiple muscles that make up the hamstrings.
Another feature of the posterior knee is the gap behind the knee, where there’s a distinct lack of soft tissue; this is known as the popliteal fossa. In the deeper muscle layer of the posterior knee, you’ll find the popliteus and plantaris muscles.
Deeper still, you’ll find the posterior capsule of the knee joint and some important nerves that run along the back of the knee. (These nerves are often a common source of pain.)
Alright! With that brief overview of the anatomy of the back of the knee, we can explore some of the most common diagnoses for posterior knee pain.
Knee Pain Caused by Nerve Aggravation (Sciatica)
This is an incredibly common cause for pain in the back of your knee. As an official diagnosis, it refers to aggravation or compression of the sciatic nerve (which runs from the low spine down the back of your leg).
Most often, sciatica is caused by compression of the nerve roots in either your lower back or from soft tissue in the buttocks. People often describe the sensation as a pain that travels or shoots down their limbs, commonly hitting that tender spot behind the knee.
Sciatica is typically diagnosed in your 50s, though it’s possible for it to start as early as your 20s or 30s. Research estimates that, on average, you can have up to a 40% chance of experiencing sciatica at some point in your life.
Luckily, though, since it’s a common diagnosis that afflicts a wide population, there’s plenty of research surrounding methods for alleviating that radiating pain.
The most effective solution is to seek physical therapy. Your treatment will likely focus on improving movement patterns — that is, working on your movement during activities that compress or load the lower back. Depending on your general lifestyle habits, this could include anything from stretching to core strengthening, or lifting education and manual manipulation of the tissues.
Because sciatica is (usually) most noticeable with prolonged standing and walking, much of your treatment will focus on the tissues in your hip flexors and gluteal muscles. Improving the flexibility of these tissues will better your walking gait, consequently decreasing the forces placed on your lower back. You can also practice some simple self-traction while sitting or standing to quickly alleviate your symptoms (in addition to those longer-term fixes!).
Knee Pain Caused by Larger Muscle Groups
As we travel further down the kinetic chain, we now have to address some of the larger anatomical systems in place. That is, the muscle groups that are directly linked to the knee itself — in this case, the calves and hamstrings.
Your calf muscles make up the back portion of your lower leg, while the hamstrings are the large muscles in the back of your thighs. Because both of these muscle groups sort of “sandwich” your knee joint, there’s a high likelihood that injury or deficiencies within these tissues can lead to subsequent pain behind your knee.
Let’s dig into some of the most common diagnoses!
Proximal Calf Strains
Your calf muscles connect to the back of your knee at the bottom of the joint — meaning that any problems or compensations with this muscle group can have a major impact on that area of your joint.
Calf strains are more commonly associated with individuals who live relatively active lifestyles. Since your calf plays a primary role in forward or vertical propulsion (i.e., that “pushing off” motion), calf strains often come hand-in-hand with activities like running, sprinting, or jumping.
That being said, it’s not unusual for people to strain their calves with everyday activities, too. Frequently climbing stairs or hiking can place excess strain on the calf, especially if the muscle is weaker or less flexible than is ideal.
It’s recommended to first address a calf strain with stretching, ice, heat, and targeted strengthening exercises. Decreasing the aggravation and tightness is part of the initial recovery, and transitioning into developing flexibility and strength will help rebuild the muscles to peak functionality. As you progress further, you can also incorporate some eccentric calf strengthening exercises (which are particularly beneficial for supplementing stair climbing or hiking).
Low Hamstring Strains
Similar to calf strains, hamstring strains often occur in more athletic populations, particularly for athletes that tend to sprint or recruit quick bursts of speed in their training. And most often, their posterior knee pain is chalked up to a distal hamstring strain.
Your hamstring muscles are responsible for controlling the forward “swinging” motion of your lower leg during your walking or running gait. If bringing your leg forward happens too quickly or with too much force, there’s a chance you may pull or strain the hamstring muscles. Depending on the severity of the strain, your muscle fibers may sustain small to large tears in the tissue, which is the cause for that symptomatic pain in the back of your thigh and knee joint.
After letting the injury heal initially, one of the best ways to thoroughly recover from a hamstring strain is to focus on eccentric strengthening drills (i.e., exercises that load the muscles while they’re lengthening). Working specifically on eccentric loading will strengthen the hamstrings as they’re elongated, which emulates similar mechanics as running or sprinting.
Tight Hamstrings or Neural Tension
Many people end up experiencing tight hamstrings despite stretching on a regular basis. (In the modern age of desk jobs and working from home, a large portion of the population sits for prolonged periods of time. When your knees are bent, your hamstrings remain in a flexed, shortened position, causing tightness and inflexibility in the back of your thigh.)
Sometimes this tightness will be alleviated with more consistent, targeted stretching. But if you’re diligent about it and still don’t feel any changes in your flexibility, your tight hamstrings may actually be a symptom of neural tension.
Neural tension typically starts within the sciatic nerve and mimics a similar sensation as tight hamstrings, but you’re also more likely to experience a sharper feeling in the back of your knee when stretching.
Knee Pain Caused within the Joint Structure
Unsurprisingly, pain behind the knee can also be correlated with issues within the knee joint itself.
Because the joint has such a complex structure (what with its connections to numerous muscles, ligaments, tendons, and bony structures), any deficiency or injury has the potential to impact the kind of pain you experience.
However, when we’re looking specifically at pain behind the knee, there are two primary culprits…
There’s a good chance that either you or someone you know has had a meniscus tear — approximately one million meniscus surgeries are performed each year.
For a quick recap, your meniscus is a cushiony disc of cartilage that sits between the heads of your large leg bones (the femur and the tibia). It’s built to withstand compressive and shear forces during movement, making it an ideal structure for absorbing shock. But in the event that there’s too much force or torque (particularly with weight bearing activity), the meniscus can tear, often resulting in a popping, clicking, or snapping sound that leads to swelling, decreased range of motion, and pain in the knee.
As a whole, the meniscus wraps around both the front and back of the knee, so sustaining a meniscal tear is an extremely common cause for posterior knee pain.
When seeking physical therapy to rehabilitate from a meniscus tear, you’ll primarily be focusing on three main aspects: lower extremity alignment, hip strength, and manual therapy to restore full range of motion at the joint.
On a less severe note, some people may also experience posterior knee pain as a result of a Baker’s cyst. (Or, as it’s often described, when it feels like there’s a “ball behind your knee.”)
A Baker’s cyst is nothing more than a fluid-filled pouch that develops in the back of the knee, secondary to injury within the knee joint or soft tissue. Though it’s a benign physiological reaction, the fluid takes up space behind your knee, ultimately limiting your ability to squat, stand, or effectively perform movements that require knee flexion.
In this case, your surrounding tissues and anatomical structures have to compensate during activities that require knee bend, which is what causes that pain behind the knee. So, while the cyst itself is pretty harmless, it inconveniences you to a point where your biomechanics have to compensate for insufficient knee flexion.
Thankfully, treating a Baker’s cyst typically doesn’t require a lot. You can generally alleviate the issue with conservative measures like icing, wrapping, and physical therapy to improve range of motion and overall functionality.
(In some cases, the fluid may need to be drained by aspiration, though it can still return depending on what underlying pathology was causing the swelling in the first place.)
Bottom Line: Knee Pain is Complicated
As with any article talking about common diagnoses for a certain type of pain, it’s important to take this information with a grain of salt — if you’re experiencing pain behind your knee, it’s not guaranteed that you have one of these specific issues.
There are many more factors and pathologies that could yield similar symptoms. But, hopefully this blog serves as a helpful starting point in understanding what kind of pain and potential severity you’re dealing with.
Your local physical therapist is the best resource to consult for questions about general posterior knee pain, what your particular symptoms indicate, and what potential options exist for alleviating your symptoms for the long haul.
Originally published 09-01-2016, updated on 11-17-2021