Knee Anatomy: A Plain Guide to the Parts of the Knee

Knee anatomy is simpler than the diagrams suggest. Three bones meet there: the thigh bone, the shin bone and the kneecap, with the thin fibula alongside. Smooth cartilage and two crescent shaped pads called menisci sit between them. Four main ligaments tie the bones together, two tendons move the joint, and small fluid cushions called bursae let it glide. I teach the Feldenkrais Method®, so I also care how all of this feels from the inside.

Knee anatomy begins with three bones

The thigh bone, or femur, ends in two rounded knuckles. They rest on the top of the shin bone, the tibia, which is nearly flat, like a small table. That is why the knee leans so heavily on the soft tissues around it.

The kneecap, or patella, is a small bone wrapped inside the tendon of the front thigh muscle. It rides in a groove on the femur and works as a pulley for that muscle. The thin fibula sits beside the tibia on the outer side. It is not part of the knee joint, but one of the four ligaments anchors to its top.

Cartilage and the two menisci

Each bone end wears a coat of smooth, slightly springy cartilage with no nerves or blood supply of its own. It feeds by being squeezed and released as you move, which is one reason a knee that sits still for hours feels stiff at first.

Between the femur and the tibia lie two menisci. Each is a crescent shaped pad of tougher cartilage, one inner, one outer. They deepen that flat table and spread your weight over a wider area. The inner meniscus is tied to the ligament beside it and moves less. Only the outer rim of each has a blood supply, so some tears mend on their own and others do not.

The four main ligaments

Ligaments join bone to bone, and four do most of the work at the knee. Two cross inside the joint, the cruciate ligaments. The anterior cruciate ligament, the ACL, runs from the back of the femur to the front of the tibia and stops the shin sliding forward. The posterior cruciate ligament, the PCL, runs the other way and stops it sliding backward. Together they form an X that keeps the joint centred as it bends.

Two more run along the sides. The medial collateral ligament, the MCL, is a broad band on the inner side that resists any push driving the knee inward. The lateral collateral ligament, the LCL, is a thinner cord on the outer side, running to the fibula, and resists the opposite push. All four are full of nerve endings that report where the joint is.

Tendons, and a short word on muscles

Tendons join muscle to bone. The quadriceps tendon gathers the four front thigh muscles and attaches them to the top of the kneecap. The patellar tendon continues from the bottom of the kneecap to a bump on the front of the shin. When the front thigh shortens, it lifts the kneecap, and the kneecap pulls the shin straight. The hamstrings at the back do the bending, with help from the calf. The knee muscles page introduces each of them in detail. Muscles are the movers; everything else here is what they move.

The bursae of the knee

A bursa is a small flat sac holding a thin film of fluid. Bursae sit wherever skin, tendon or muscle would otherwise rub on bone. Four of the knee's dozen or so are worth naming.

The prepatellar bursa sits in front of the kneecap, just under the skin. It takes the pressure when you kneel; our guide to prepatellar bursitis covers that swollen, tender front of the knee. The two infrapatellar bursae sit below the kneecap, one over the patellar tendon and one beneath it. The pes anserine bursa lies on the inner side of the shin, a few finger widths below the joint line, where three tendons fan out like a goose's foot. The suprapatellar pouch sits above the kneecap, between the quadriceps tendon and the thigh bone, and opens straight into the joint. So a knee that swells from the inside often looks fuller above the kneecap.

Knee anatomy in motion: a hinge that also turns

Most of the time the knee behaves like a hinge: it bends and it straightens. But it is a hinge with a twist. As the knee straightens the last few degrees, the shin turns outward a fraction and the joint locks, which lets you stand with very little muscle effort. To bend again, a small muscle behind the knee turns the shin back and frees it. Once bent, the shin can rotate a little in both directions. As it bends, the femur rolls then glides on the tibia, and the menisci slide along.

How the hip and ankle shape the knee

The knee lives between two very different neighbours. Above it is the hip, a deep ball and socket that can turn the whole thigh in any direction. Below it are the ankle and foot, which can roll the shin inward or outward with each step. The knee has little say in where it points; it receives what the hip and the foot hand to it. If the thigh turns in, or the foot rolls in, the knee follows and the ligaments on one side work harder.

This matters because the knee is where osteoarthritis, the slow wearing of joint cartilage, shows up most often. An estimated 365 million people have it at the knee, more than at the hip or the hand, which come next (WHO, 2023). I am not saying habits cause it. But the way the hip and foot divide the work alters what a knee feels like day by day, whatever the state of its cartilage. The Feldypedia entry on knee stiffness after 60 looks at how joints change with age.

Sensing the knee from the inside

Every ligament, meniscus and tendon carries tiny sensors that report where the joint is and how loaded it is. Together they give you proprioception, the sense of your knee's position without looking. A knee that has been sore for a while often sends a fuzzier picture, so the muscles around it brace. Slow, gentle movement gives those sensors something clear to report, and the bracing tends to soften.

Try it: sit with both feet on the floor, slide one foot forward a few inches and back, and feel the kneecap glide in its groove. Then compare the other side. That is the idea behind the knee proprioception exercises here, and the kind of noticing an Awareness Through Movement® lesson is built from. The Feldy online movement program offers a free 7 day trial, no credit card needed, and the knee and hip page shows how they are shaped for a tender knee.

Alongside clinical care and other methods

Knowing the knee does not replace having it examined. If a physiotherapist, orthopaedic doctor or osteopath is looking after your knee, this work sits beside their plan. Yoga, Pilates, tai chi and strength training also work with the knee, each through its own mechanism. Yoga tends to build range through held shapes, and Pilates builds control through precise, repeated movements. Feldenkrais works through very small, slow movements and attention, and is soft enough for a knee that dislikes load. They are different doors into the same room.

When knee pain needs a clinician

Some signs mean the knee needs a professional look before any home practice. If you cannot put weight on the leg, or the knee locks so it will not fully bend or straighten, book an appointment. The same goes for a knee that gives way under you, or one that is hot, red and swollen, especially with a fever. Pain that began with a fall, a twist or a direct blow also deserves an examination. Gentle movement can wait a week. A knee like that should not.

Find where to start

You now know the parts, and you have felt at least one of them move. The next question is which way of working suits you.

Now that you know your knee's parts, which way of moving would suit them? Movement Match asks a few short questions and points you to the method, Feldenkrais, Alexander Technique, yoga, Pilates or tai chi, that fits how you like to learn.

Common Questions about knee anatomy (FAQ)

Is it safe to explore knee movement at home if I have arthritis or an old injury?

Usually, yes, provided you keep each movement small, slow and comfortably inside your easy range. Osteoarthritis and old injuries usually settle better with gentle motion than with rest. Ask a clinician first if the knee is swollen, hot, locking or giving way, or if you have had surgery recently and have not been cleared to move it.

How often should I spend a few minutes sensing my knees?

A couple of minutes most days works better than one long session a week. You can do it sitting at a desk, waiting for a kettle, or before a walk. Because the movements are tiny and stay comfortable, there is nothing to recover from. What you are building is familiarity, so a softer way of working has the chance to become familiar.

How long before a stiff knee starts to feel easier?

Many people notice a small change within one session: the kneecap glides more freely, or the thigh grips less. That first change may fade by evening, and that is normal. A steadier shift, where stairs and chairs feel easier by default, often takes a few weeks of short daily attention. If several weeks bring no change at all, that is worth mentioning to a clinician.

How is the knee joint different from the hip joint?

The hip is a ball and socket. The rounded head of the thigh bone sits deep in a cup on the pelvis, so it can swing, spread and turn in every direction. The knee is a modified hinge: two rounded knuckles rest on a nearly flat surface, held by ligaments and menisci, and it mainly bends and straightens with a little turn at the end. Because the hip can turn the whole thigh, it decides much of where the knee points.

What is the best way to look after your knees?

Keep them moving through their full range often, and let the hip and the foot share the work. Walking on varied ground, rising from a chair slowly, and a few minutes of gentle sensing practice all give the cartilage its regular squeeze. Strength work from a physiotherapist adds support around the joint. Awareness work sits alongside that and asks whether the knee is receiving more twist and load than it needs from the joints above and below.

What should I avoid when my knee is sore?

For a few days, rest from deep squats, kneeling on hard floors, forceful stretching and long walks downhill. Avoid pushing the knee into a bend or a straightening that hurts, and avoid standing with the knees locked back. Let the ache decide how big each movement gets. Should swelling, heat or a sense of the knee giving way appear, stop home practice and have it checked.

When does knee pain need a doctor rather than home practice?

See a doctor promptly if you cannot bear weight on the leg, the knee locks or gives way, or it is hot, swollen and red, especially with a fever. Pain that started with a fall, a twist or a blow to the knee also needs an examination first. A knee that keeps getting worse over a couple of weeks, instead of settling, is worth a visit too.