Do your knees feel stiff after sitting for prolonged periods of time?

Here’s a fact – your joints like to be moved. The movement helps keep them lubricated which allows better movement within the joint. If you are working from home, you are probably sitting at your computer for longer periods of time. You probably sit down first thing in the morning and don’t move again until lunch. You have less work-related breaks at home due to your coworkers being virtual…basically, there’s no need for you to get up. When you finally get up, your knees feel stiff and sore.

You’re probably thinking, but my knees are relaxed while I’m sitting so why would they feel stiff and sore? That is correct the knee joint is relaxed and unweighted. However, the musculature surrounding the knee joint is stressed at different points which puts stress on the knee joint. It doesn’t matter whether you sit with one leg under you, legs crossed, legs extended out in front, or properly sitting with your feet flat on the floor. All these positions can be stressful when kept for prolonged periods of time.

Anatomy

As you can see in the picture above, the knee has a great deal of muscle and ligament attachments. This works out well for us to be able to move and perform activities we love. However, it also means that there is a higher chance of something having a dysfunction. The good thing about the knee is that it only moves in two directions, bent (flexion) and straight (extension). The knee cap (patella) lays on top of the joint which is comprised of your thigh bone (femur) and your main shin bone (tibia). You do have a non-weight bearing shin bone (fibula) that lays on the outer portion of your shin. This does not make up your knee joint, but it does allow for muscles and ligaments to attach to it. In between your femur and tibia there is a cushion called your meniscus. The meniscus is a layer of cartilage that allows our bones to move smoothly on each other. There are parts of the meniscus that have great blood flow and others that do not. Other major ligaments are your ACL (anterior cruciate ligament), PCL (posterior cruciate ligament), MCL (medial collateral ligament), and your LCL (lateral collateral ligament). These 4 structures help maintain the integrity of your knee with movement. It helps us feel supported and stable. The ACL and PCL are deep in the knee joint, preventing forward (anterior) or backward (posterior) movements of your femur on your tibia. Your MCL and LCL lay on either side of your knee to support sideways movements. Two major tendons help form the knee joint, one being the patellar tendon that goes from your knee cap to a bony protrusion on your tibia and the quadriceps tendon which goes from your quadriceps muscle to the top of the knee cap.

Now that you know what the knee joint entails, let’s dive into why when you sit for prolonged periods of time your knees feel stiff when you get up. Remember, joints like movement. If we don’t allow our knees to move, they are not getting the proper flow of lubrication. So, when you go to stand up, your joints are “dry”. It takes a few steps to get the nutrients flowing, which allows the knees to become lubricated once again resulting in less stiffness.

Sitting Positions

Depending on what position you choose to sit in, your muscles and ligaments will take a toll. A muscle doesn’t always have to be in a shortened position to have tightness. Over stretching the muscle for prolonged periods of time can also lead to tightness. Any drastic change in muscle fibers can cause a dysfunction that can affect multiple muscles.

Sitting with One Leg Under You

Shorted muscles – hamstrings, abductors (muscles on outside of thigh), hip flexor

Lengthened muscles – quadriceps, adductors (inner thigh muscles)

Ligaments – all 4 will be stretched

Tendons – patella and quadriceps will be stretched

Legs Crossed

Shortened muscles – adductors, hip flexor

Lengthened muscles – hamstrings, quadriceps, abductors

Ligaments – LCL stretched, MCL relaxed

Tendons – slightly stretched

Legs Extended in Front of You

Shortened muscles – quadriceps

Lengthened muscles – hamstrings, abductors, adductors, hip flexors

Ligaments – back of the knee capsule is stretched, straining both ACL and PCL

Tendons – relaxed

Feet Flat on the Floor

Shortened muscles – hip flexors, hamstrings

Lengthened muscles – quadriceps

Ligaments – neutral position

Tendons – slightly stretched

As you can see, there are many factors that play a role with the position of our legs while sitting. Even the form that is supposed to be proper form can cause pain, if sustained for too long.

Stay tuned for Friday’s post to see how to combat the stiffness and pain in your knees from sitting too long!

Disclaimer: I am in no way diagnosing anyone, if you have persistent pain you need to call your local physical therapist and schedule an appointment.