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March 27, 2020 9 min read

If your joint does not have a full range of motion in all directions or you feel pain during your workouts, you might have a problem. You can try to manage it for a while, but eventually, the pain will send you to the doctor. Knee extension deficits happen with age, after serious injuries, ligament reconstruction or rupture, or knee replacements. There are various causes for loss of terminal extension, from mechanical pathology to hamstring contracture and quadriceps inactivation.

If you fully extend your knee, you know there’s an issue. Don't take it lightly. Things can become severe. Without the ability to perform the full range of motion, you are exposing your joints to overloading. That results in distinctive mechanical disadvantages. You can experience acute and chronic performance deficits, which will interfere with your training goals as well as your daily life.

The Pain is Light, Do I Need to Worry?

There are several tests to perform in order to explore the knee ROM. 

  • Sit on the floor and try to lift your lower leg using its muscles. If your knee is injured, you will probably need some assistance to lift your lower leg and fully extend the knee. If you can perform this on your own, only with slight pain, start using a knee immobilizer. It will help with the pain to hold the knee in a straight position. Use it merely until you get the appointment with your physical therapist. Whatever you do, don’t wait too long!
  • Lie down and straighten your leg. If you can not reach the full knee extension due to the pain, that is a warning sign. If you are totally unable to straighten your knee, that is a big red flag, and you need a doctor as soon as possible.

Some of the causes for a locked knee include meniscus tears, patella fractures, quadriceps tendon tears, patellar tendon tears. Any of those can be associated with an inability to straighten the leg. It is important to check whether you can't straighten your knee due to the pain only, or the reason is a physical blockage too. Pain can come from some temporary causes, and the obstruction can signal the real issue.

The other side of the problem is when you have trouble bending your knee. If your knee feels stuck in any way and remains like that, it is a sign your condition needs professional treatment.

What Makes the Terminal Knee Extension so Important

The muscles responsible for knee extension are hamstrings and quadriceps. Hamstrings reinforce the action of the quadriceps muscles by pulling the knee posteriorly, during extension and hyperextension. 

A full knee extension is essential for optimal quad force production, and vice versa. The loss in quad function increases joint loading, which destabilizes the knee joint through a reduced extension torque. In the same way, without the full range of knee motion, the quadriceps will deteriorate in time. 

Healthy knees can move into hyperextension for about 5 degrees past neutral. Knees with problems can not reach the neutral extension at all, at least not without pain.

A fully extended knee is also called the close-packed position of the knee. It is the position where the ligaments reach the highest tension. The articular surfaces are the smoothest. If you load up pressure on your leg, it will spread out evenly, and the knee will remain stable. Without reaching the full extension position, the weight can't spread the way it should. 

Whether it's a deadlift or jumping, the system will be unable to spread the load across the joint surface. Continual loading of the area will cause too much friction in the joint and put too much pressure on the cartilage, getting in the way of its role of shock absorption. In time, the cartilage will become damaged or even deteriorate. The knee's normal movement becomes limited and followed by significant pain. Think of the early arthritic changes. Nobody wants a hole in their knee.

Don’t forget, the lack of a terminal knee extension keeps you from being able to lock out the knee, which can lead to Patellofemoral Pain Syndrome. If a knee never gets entirely straight, then it will put constant stress on the patella tendon. It's characterized by the pain at the front of your knee around your patella/kneecap. We also know the condition as "the runner's knee." This is especially common in athletes, especially with sports that involve running and jumping. This kind of pain will get worse while running, climbing the stairs, or performing movements like squats. Ice sprays and cooling gels help, but if the pain is persistent, it's better to consider physical therapy.

Knee Pain Is the First Link in a Chain of Problems

The loss of terminal knee extension can cause issues through your entire kinetic chain. The body is connected, from muscles to bones. Every sport, and the majority of daily activities, require the ability to keep the knee straight. Your hamstring muscles are responsible for bending your knee and extending your hip backward. When the knee is not fully functional, consequently the hip cannot get into a neutral extension. 

The chain problems continue by overextending at the lumbar spine, which then struggles to keep you standing up straight. Making this situation longer and adding extra loads during training is the road to make problems like spondylolisthesis worse. Spondylolisthesis is a spinal condition that affects the lower spinal bones. Read that as "more and more pain." The ankles also have to overcompensate, leading to lowered performance and possible injury. Proper knee exercise techniques can, luckily, improve the whole chain of problems.

Restoring terminal knee extension is among the first acts in rehab after knee replacement surgeries and as post-knee injury treatment. Some of them are not much different from quad-strengthening training, only with lower resistance. The purpose is to mobilize the joint into the position of restriction and activate the quads. Gaining back strength is an essential step in obtaining full functional mobility and a full recovery.

The Knee Range of Motion

The normal range of motion, when the anatomical position is zero degrees:

  • Flexion = 0 to 140 degrees. 
  • Extension - zero degrees = full extension. Every degree subtracted from the formula marks the limitation in ROM.
An elastic workout band.

Terminal Knee Extension Exercises

American Academy of Orthopaedic Surgeons puts knee exercises as one of the most important parts of healing and restoring mobility and strength in a painful knee. Terminal knee extension workout sets a range of motion to put your knee to move. There are several sets of exercises frequently recommended by doctors and therapists. Those include sitting, standing, or lying position. It would be smart to consult your physical therapist before any attempt to do terminal knee extension exercises on your own. Never forget to warm up before a workout.

Standing TKE

The standing terminal knee extension (TKE) is an effective and easy way to strengthen your quads. Since your quads are working to support your body weight, the standing TKE is considered a functional exercise. To perform the standing terminal knee extension, you will need a resistance band. Your physical therapist can provide you one.

You need to make sure the resistance band is anchored around the height of your knee. The best way to secure the band is to tie it around a stable object. If you do the exercise in a gym, ask your trainer what to use. You can choose between lighter weights on a cable system or a resistance band. Your trainer should have advice on how to incorporate TKE variations in your standard workout without overloading the knee.

At home, think of a table leg, bedpost, or a vertical pipe. You can also go outside and use a tree.

  • Anchor the resistance band.
  • Put the leg you want to exercise inside the resistance bend.
  • Turn to face the anchor point and slightly bend the knee.
  • Start straightening your knee slowly. That will place some tension on the resistance band.
  • When your knee is as straight as you can bring it, stop and hold the position for several seconds.
  • Return to the starting position. All the moves must be performed smoothly and slowly.
  • Do 15 reps.

Some resistance bands and cords tend to roll and bunch up in the back of your knee. You can avoid that if you apply a foam pad to your band, or put a soft silicone barrier between the band and the back of your knee. 

In time, you can start increasing the resistance to gain more strength in your quads. If the weakness of your quadriceps muscles is the root of the issue, you will notice the progress in no time.

Sitting Knee Extension

  • Sit on the floor.
  • Keep your body upright with your knee slightly bent.
  • Use a cylindrical object to support the back of your knee. If you workout at home, the pillow or rolled towel will do the trick.
  • Alternatively, you may sit on the chair with an extension, using the latter to support the back of your knee.
  • Flex your foot back and focus on contracting your quadriceps muscles. Return to the starting position.
  • You should do three sets of 10 to 15 reps for one leg. 

Lying Knee Extension

  • Lie down flat on your back.
  • You can support yourself on your forearms to keep your head and shoulders off the floor.
  • Support the back of your knee with a cylindrical item. Slowly bend the knee at a 30-degree angle. 
  • Keep the other leg straight.
  • Start contracting your thigh muscles. Hold as tight as possible for three seconds. 
  • Slowly lower your heel to the floor and return to the starting position.
  • Make three sets of 10 reps for each leg.

It is essential to remember to keep it slow and steady, with no sudden moves. Your knee should be in line with your toes. Unnecessary twists and deviations will put an excessive strain on your knee.

Once you are comfortable doing the TKE, you can make it more challenging. Try placing a small foam pad underneath your stance foot. That will add a dimension of balance to your exercise and make it multifunctional.

Do your best to keep your quadriceps muscles strong. Recovery is never about strengthening only one place. You must not forget the hip muscles because they control the knee. It will help you to maximize your mobility and decrease the risk of further injuries. Be sure to pick the quad strengthening exercises which will not place more stress on your knee joint.

A girl doing wall squats.

Exercises Will Reduce Your Knee Pain

Knee problems are catching up and soon will surpass the lower back problems. They had already reached the top of the list as the most common physical injury.

In dealing with knee pain, for prevention of further damage exercise is the staple. Building strong muscles helps you to reduce knee pain and stress. It affects the knee joint’s ability to absorb shock better. Strengthening exercises improve the quad sets and hamstrings ability to remove part of the pressure from your knees.

The American Academy of Orthopaedic Surgeons put together these tips to stay safe and avoid further injury:

  • Begin slowly because recovering and gaining new strength is a gradual process.
  • When exercising, expect some discomfort but not significant pain. If you're in severe pain after a workout, to the point that it's difficult even to move, it means you've overdone your exercises.
  • Ask your doctor or physical therapist for advice about the exercise routine and get help building a solid plan.

There are various exercises you can do in the gym or even at home to reduce knee pain. The average amount is three sets of 10 reps each, but you can adapt it to your personal preferences. The key is to make the joints and muscles work, but not to force them too much.

  • Hamstring curls: Hold on to the back of a chair, face forward. Lift the right foot and move it up toward your backside to a 90-degree angle most. Hold it for three to five seconds and slowly return to the starting position. Repeat with the other leg. Try to keep your knees close together.
  • Straight-leg lifts: Lie on your back. Keep one leg straight, and the other one bent. Stiff your thigh muscles to lift your leg a few inches from the floor. Hold on for about five seconds in the air, lower it down, and repeat on the other side. Take care to keep your back straight.
  • Wall squats: Stick your back straight against a wall. Keep your feet parallel and spread hip-width apart. Gently slide down until you reach a sitting position. Pause for 10 seconds and push back up. Don't rush.
  • Single-leg dips: Stand between the backs of two chairs and lift one leg slightly in front. Bend the supporting knee to lower yourself a few inches. The key is to push your weight on the heel of the supporting leg. Hold on for about 5 seconds, return to the starting position. Repeat for the other leg.
  • Step-ups: Use a sturdy platform, low stair, mini step machine, or a low stool. Put one foot on the platform while the other foot is hanging loose. Lower the hanging foot slowly down and do the same with the other leg.

Once you get comfortable with these exercises, you may start adding weights for an additional challenge. Any or all of the knee extension exercises can be incorporated in your standard workout routine. Talk to your trainer and be creative. 

Never forget to stretch after a workout, to downsize soreness and keep your muscles flexible. You want to avoid muscle over-tightening. Too tight muscles lead to injury and can enhance the knee pain.

Respect Your Joints 

Some people have naturally better flexion and extension in their knee joints. Others have limitations and conditions like osteoarthritis to overcome. Keeping (or gaining back) knee flexion, extension, adduction, abduction, and rotation should be a permanent goal. Exercising and diet will bring progress. It is not something that happens overnight, but continuous efforts give many results. Working on your knee extension can also remove back pain, hips problems, and improve the overall posture.