Does your knee hurt while you climb up or get down the stairs? Does your knee get stiff when you try to move it after sitting for long hours?If your answer is yes on both counts, then your knee definitely demands medical attention.Does your knee hurt while you climb up or get down the stairs? Does your knee get stiff when you try to move it after sitting for long hours?If your answer is yes on both counts, then your knee definitely demands medical attention.The knee joint is formed by the lower end of the femur bone (thigh bone) and upper end of the tibial bone (shin bone) placed one over the other with a layer of cartilage on the surface of the bones. In between, is a cushion-like structure called meniscus, which acts as a cushion between the two bones, absorbs shocks and prevents wear and tear caused by bone-to-bone connect.There are four ligaments attached in between the bones that hold the knee joint together and add stability to it. The quadriceps group of muscles that are in the front of the knee help in extension/straightening of the knee, while the hamstring group of muscles helps in bending it.Having now understood the ‘make-up’ of the knee joint, now let us understand why does it hurt.While we perform our day-to-day activities — walking, climbing stairs, sitting down, running, etc. — there is immense pressure coming on these internal structures of the joint. On every step that we take, our knee handles about 2.5 times our weight. This means, if you weigh 60kg and walk five steps, your knee bears a total weight of 60 * 2.5 = 150kg, and 150 * 5 = 750kg.Yes, that’s right, load bearing of 750kg in just five steps! The maximum work of this load bearing is done by the meniscus and the cartilages. While the ligaments do the job of aligning the joint and giving stability to it. The muscles around the knee joint help to initiate the desired movement, take the load off the joint and control the joint activity. If any of these load-bearing muscles is weak, then there is direct pressure on the meniscus, cartilages and the ligaments. Which, in turn, causes a high level of wear-and-tear at the joint level.The fact lies that the blood supply to these cartilaginous structures is very poor and once the wear and tear happens, they get damaged and the healing takes a lot of time. As the knee cushion starts to wear, the bone-to-bone proximity and friction increases, and small particulates of the bones start to form and occupy the joint space. This degenerative or ageing process is called arthritis. Once this begins to happen, auto-protective mechanism of the body comes in play, and it stiffens up the muscles around the knee joint (that is, tight quadriceps, tight hamstrings) further limiting the range of motion of the joint. That is why your knee stiffens up when you are in pain.So, what can we do about this?Of course, the ageing cannot be stopped but it can definitely be slowed. And the answer is by maintaining a good level of muscle strength so that they can match up with your activity level. And, at the same time, maintain the length of the muscles by following a routine that allows for stretching exercises.A few simple basic exercises will help you maintain good muscular strength and could help keep knee aches and pains at bay.