The knee is one of the most important joints in the body, and it is also one of the most commonly injured. In my practice, I often meet Bangladeshi patients who say, “Doctor, I know my knee hurts, but I do not know what part is actually damaged.” That is a very common concern. The knee is not a simple hinge. It is a complex joint made up of bone, cartilage, ligaments, menisci, muscles, tendons, and a joint lining that all work together to support walking, stair climbing, squatting, kneeling, prayer movement, running, and balance. [1]
When patients understand knee anatomy, they usually understand their pain better too. They can make more sense of terms such as meniscus tear, ACL injury, cartilage wear, arthroscopy, or knee replacement. That knowledge does not replace medical evaluation, but it does make the next step much clearer.
Why knee anatomy matters
The knee has two major jobs at the same time. It must be stable enough to carry body weight and flexible enough to bend, rotate slightly, and adapt to uneven ground. That balance is what makes the knee so efficient, but it also makes it vulnerable when one structure is overloaded or injured.
For many people in Bangladesh, the knee works hard every day. Long periods of standing, repeated stair use, sitting on the floor, squatting for household tasks, sports, and travel on uneven roads can all stress the joint. When pain begins, the problem is not always in the same part of the knee. Sometimes the bone surfaces are involved. Sometimes the meniscus is torn. Sometimes the ligaments are stretched or torn. Sometimes the kneecap is not tracking well. That is why a careful understanding of anatomy matters.
The bones that form the knee
Three bones form the main structure of the knee:
- femur, or thigh bone
- tibia, or shin bone
- patella, or kneecap
The lower end of the femur and the upper end of the tibia form the main weight-bearing joint. The patella sits in front of the knee and helps the quadriceps muscle straighten the leg more efficiently.
The fibula is the smaller bone on the outer side of the leg. It does not carry the main weight through the knee, but it still has important attachments for nearby ligaments and soft tissues. When I evaluate knee pain, I start with the bone framework because it helps patients understand fractures, arthritis, alignment problems, and kneecap issues in a practical way.
Cartilage: the smooth surface inside the joint
The ends of the bones are covered by articular cartilage. This is a smooth, slippery surface that helps the joint glide with low friction and spread force more evenly.
Healthy cartilage allows comfortable movement. Damaged cartilage can lead to pain, swelling, stiffness, clicking, or catching. Cartilage injury may happen after trauma or sports injury in younger people. In older adults, it may develop gradually as part of osteoarthritis.
Many patients in Dhaka first hear the word “cartilage” after an X-ray or MRI. The scan may show wear or damage, but the symptoms usually begin earlier with activity pain, swelling, or reduced confidence in the knee.
Menisci: the shock absorbers of the knee
Inside the knee are two C-shaped cushioning structures called the menisci:
- medial meniscus, on the inner side
- lateral meniscus, on the outer side
I usually explain to patients that the menisci are not just padding. They also help distribute load, improve stability, and protect the cartilage over time.
What the menisci do
- spread body weight across the joint
- reduce pressure on the cartilage
- improve joint stability
- support smooth motion
- reduce wear over time
A torn meniscus is one of the most common knee problems I see. It may cause pain, swelling, locking, catching, or pain during twisting movements. In younger patients it often follows a turning injury. In older patients it may occur gradually with degenerative change. Understanding the meniscus helps patients make sense of MRI reports and of treatment options such as physiotherapy, injection in selected cases, or arthroscopic treatment when it is appropriate.
Ligaments: the stabilizing bands
Ligaments connect bone to bone and provide stability.
The major ligaments of the knee are:
- ACL, or anterior cruciate ligament
- PCL, or posterior cruciate ligament
- MCL, or medial collateral ligament
- LCL, or lateral collateral ligament
The ACL and PCL are inside the joint and help control forward-backward and rotational stability. The MCL and LCL support the knee from the inner and outer sides.
When a ligament is torn, the knee may feel unstable or “give way,” especially during twisting, running, sudden stopping, or walking on uneven surfaces. A patient may still be able to walk after an ACL injury, so pain alone does not tell the full story. Stability is just as important as pain.
The kneecap and the front of the knee
The patella, or kneecap, moves within a groove at the lower end of the femur. It improves the power of the quadriceps muscle, which helps straighten the leg.
When the kneecap does not track properly, front knee pain can develop. Patients may notice pain while climbing stairs, squatting, kneeling, sitting with bent knees for a long time, or getting up from the floor. This is common in patellofemoral pain, runner’s knee, cartilage softening around the kneecap, and patellar instability.
In Bangladesh, repeated stair climbing, long commutes, poor footwear, and weak thigh or hip muscles can add to this problem.
Muscles and tendons around the knee
The knee does not work alone. Muscles above and below it guide movement and absorb force.
The quadriceps in the front of the thigh straighten the knee. The hamstrings at the back of the thigh help bend it and contribute to stability. The calf and hip muscles also affect how the knee moves.
Tendons connect muscle to bone. The quadriceps tendon above the kneecap and the patellar tendon below it are especially important.
If the muscles are weak, tight, or poorly coordinated, the knee may take more stress than it should. That is one reason physiotherapy, strengthening, and movement retraining are often part of good knee care.
The synovium and knee swelling
The inside of the knee is lined by the synovium, a thin tissue that produces synovial fluid. This fluid helps lubricate the joint and support cartilage health.
When the knee is irritated by injury, arthritis, inflammation, gout, or infection, the synovium may produce extra fluid and the knee swells. Swelling does not always mean a severe injury, but it does mean the joint is reacting to something.
