The knee joint is comprised of connections between the femur, patella, tibia, and fibula. These bones have various muscle, tendon, and ligament attachments that create a hinge joint allowing for knee extension and flexion. The thigh bone is commonly understood as the femur, and the shin bone consists of the tibia and its partner, the fibula. The knee cap is the patella. Straightening out the knee joint and aligning the thigh and shin bones is knee extension. Shortening the joint angle and moving the shin bone closer to the thigh bone is knee flexion. This simple movement of bending and straightening the knee is an important component of daily functioning. For those of us who don’t think twice about how our knees bend and extend, perhaps it would be helpful to put ourselves in the shoes of the people dealing with afflictions to their knees that don’t bend or extend without extra effort, preparation, muscle stiffness and weakness, or bone-on-bone pain.
Forward strides in walking, stair climbing, and standing up from a seated position require the spine, hips, knees, ankles, and feet to work in unison. When a joint is impeded by muscle weakness, joint stiffness, or structural damage to the connective tissue of one of the joints, lower-extremity movement can be hindered. A few examples might include advanced cases of arthritis causing bone-on-bone contact due to cartilage degradation, damage to the structurally supportive tissues such as tendons, ligaments, or menisci. Deconditioning of muscles during the recovery process after knee replacement surgery or a previous injury can also affect knee health.
The two large muscle groups that power knee flexion and extension are the quadriceps and the hamstrings. Originating at the anterior portion of the hip, tracing down the front of the thigh, and attaching onto the proximal portion of the shin just below the knee cap, the quadriceps acts as a pulley that brings the shin toward the front of the body and extends the leg to a straightened position. The hamstring is located on the posterior aspect of the thigh, originating just below the gluteal fold, extending along the posterior thigh, and attaching to the posterior aspect of the tibia and fibula. Similar to its neighbor, the quadriceps in the front of the body, the hamstring acts as a pulley, bringing the leg from an extended to a flexed position.
While numerous muscles act as vital knee movers and stabilizers, the quadriceps and hamstrings have large surface areas that cover much of the thigh and produce significant movements that support the hinge-joint properties of the knee, which are bending and straightening. The knee joint is held together by various ligaments that cross the knee. These ligaments act as brackets to maintain the integrity of the joint. The knee is also equipped with a cartilaginous pad between the thigh and shin bones, which provides cushioning during lower-extremity compressive forces while walking, stepping down, or standing up from a seated position. These deep intrinsic connective tissues of the knee, such as the cruciate ligaments and meniscus, don’t heal the same way skeletal muscle does. In fact, when ligaments and cartilage are damaged, the repercussions of injury can remain for a long time.
A productive strategy to support knee-stabilizing connective tissue is to reinforce the skeletal muscle surrounding the knee. The hamstring and quadriceps don’t only act as primary motors for significant knee movement, but they also aid in fastening the joints together so they don’t slide too far out of joint alignment. This means that with strong hamstrings and quadriceps, the integrity of knee ligaments and cartilage can be reinforced.
An exercise we conduct with our personal training clients to strengthen the quadriceps includes the seated knee extension:
To perform the seated knee extension, sit flat on the ground with optimal posture, with one knee extended where the heel is flat on the ground and the other flexed to a position where the entire foot is flat on the ground. While keeping the toes flexed toward the body, extend one leg as if attempting to touch the back of the knee, and gently contact the ground until a slight muscular sensation is experienced in the quadriceps and kneecap region. Repeat this movement for five to ten repetitions on each leg.
If we aren’t experiencing knee pain, it’s easy to bypass the need to strengthen them. However, as life stresses accumulate and age advances, knee issues may become more prevalent. Perhaps we can spend a little time strengthening the knee muscles before problems arise.
Sean McCawley, the founder and owner of Napa Tenacious Fitness in Napa, CA, welcomes questions and comments. Reach him at 707-287-2727, napatenacious@gmail.com, or visit the website napatenaciousfitness.com.