Why Does My Knee Hurt When Bending?

Why Does My Knee Hurt When Bending?

Knees take a beating all the time, but even more so when they bend. In fact, knees take a force of up to 4 times your body weight every time you move.

The knee is the largest and most complex joint in the human body. With many components such as bones, tendons, ligaments, muscles, bursae, and other soft tissues, it is very vulnerable to a variety of injuries. According to the American Academy of Orthopedic Surgeons, there were about 10.4 million doctor visits in 2010 alone for common knee injuries (fractures, dislocations, sprains, and ligament tears), so it’s no surprise that Americans are experiencing knee pain - especially when bending.

Top Causes of Knee Pain when Bending

Runner’s Knee

Runner’s knee is a painful condition that develops as a result of repeated bending of the knee joint. However, it can also occur because of poor alignment, a direct blow to the knee, or due to flat feet or weak thigh muscles. Pain from runners knee is usually just below or to the sides of the kneecap in the front. Symptoms include swelling around and behind the kneecap, knee pain when bending, possible crepitus, or cracking and popping noises in the knees when walking. Runner’s knee pain usually begins gradually and increases in severity as symptoms worsen.


Each of your knees has fluid filled sacs called bursa, which cushion and protect the structures of the knees. Bursitis occurs when the bursa become inflamed when kneeling, squatting, or in the presence of excess friction in the joint. Repetitive or prolonged kneeling or falling onto the knee can also cause inflammation of the prepatellar bursa below the kneecap on the front of the knee. Excess fluid in the knee joint that seeps back into the bursa can cause swelling and pain on the back of the knee. Although bursitis is not the most severe condition, it can cause significant discomfort.

Sprains or Injuries to Ligaments

A sprain on one of the four ligaments that help stabilize the knee can also cause pain while bending. If one of the ligaments tears or stretches too much, the pain can cause minor to severe pain. Most often the result of sports injuries, the incredibly painful and debilitating symptoms of damage to knee ligaments are most likely to be experienced by athletes.

Tears caused by repeated extension of the knee joint, impacts on hard surfaces, or abrupt shifting and twisting against the “hinge” of the knee can produce a variety of injuries in ligaments, including the ACL, PCL ,LCL, or MCL. Symptoms include pain, swelling, stiffness, and even immobility. Symptoms usually come on immediately or shortly after an injury.

Meniscus Tear

The meniscus is a thick layer of cartilage lining the knee joint to protect and cushion it. If it tears, it can no longer cushion the knee, and it can get inflamed and limit movement. If your knee pain happens mostly while squatting or using the stairs, it could be a tear in your meniscus.

Arthritis or Osteoarthritis

Inflamed joints from arthritis can also cause pain while bending. If the pain comes after sitting for a long time, or in the morning, it could be caused by arthritis. Gentle movement can help to ease arthritis pain. Symptoms of arthritis develop over time and are not constant.

Osteoarthritis is the most common form of joint inflammation and arthritis, experienced by over 30 million people annually, according to the CDC. Known as the “wear and tear” form of arthritis, it develops as a result of the continual wear on the cartilage in the knee joint. While it’s most often experienced by adults over 65, factors like genetics, obesity, diet, and existing injuries can cause symptoms of osteoarthritis to show up in adults as young as 25. Symptoms include stiffness, swelling, tenderness, and weakness.

Poor Alignment

When the body is properly aligned, the bones are stacked above each other and effectively distribute weight and force down the length of the body. When your posture is compromised or your gait is compensating for muscular tightness, weakness, or injury, a large amount of stress is created on the components of the knee joint. Having poor posture during any activity, including sitting, standing, walking, or bending, can result in pain and further injury to the knee.

Types of Knee Pain When Bending

Pain in the Knee, with “Locking” in the Joint

Inside the knee joint, there are two “C” shaped pieces of cartilage called menisci, which keep the surfaces of the upper leg bone and lower leg bones from grinding against each other. Injuries to this cartilage usually result from a trauma, like landing a jump or twisting your knee. You may also notice problems with range of motion, walking, or even a “locking” sensation in the joint. Resting the knee and managing inflammation will help heal minor tears, while physical therapy can help strengthen and stabilize it.

Pain Behind the Kneecap

Patella-Femoral Syndrome is a term that describes joint pain between the kneecap and upper leg bone. Under the kneecap is a smooth cartilage lining that creates a gliding surface between the bones, and if it softens or wears away it can result in pain and inflammation. According to Neuromuscular Specialist and co-founder of the Performance Institute in New York City, major contributing factors to this knee pain are poor alignment when landing, as well as imbalanced quadricep muscles, which can pull the kneecap side to side. Strengthening the quads and stretches to lengthen hamstrings and calfs will help reduce the risk of injury.

Pain and Tenderness on the outside of the Knee

The Iliotibial Band is a thick band of tissue that extends from the outside of the hip down to the outside of the knee. Repetitive flexion and extension of the knee, combined with lack of flexibility in the tissues can cause Iliotibial Band (ITB) Syndrome, which can put tension on the outside of the knee and result in knee pain while bending or moving. According to the Mayo Clinic, ITB Syndrome is an overuse injury. However, weak hip muscles and ITB tightness can add to the problem. Learning foam-rolling techniques can help stretch the ITB, and strengthening and stabilizing the lateral hip muscles will reduce the strain.

Pain with a Pop

The MCL (Medial Collateral Ligament) and ACL (Anterior Cruciate Ligament) are important, stabilizing ligaments in the knee that keep the joint from moving side to side. They can easily be injured as a result of trauma, such as twisting, turning, stopping quickly, or if the knee is pushed side-to-side. Pain can be felt with a “popping” sensation. Learning correct positioning and alignment can help prevent this type of injury. Healing an ACL or MCL injury usually requires treatment with physical therapy, and may include bracing to support and stabilize the knee during recovery.

How Can I Treat My Knee Pain?

Treatments at home, such as rest, ice, using bandages or bracing, and elevation can often help. If your doctor gives permission, over-the-counter anti-inflammatory medications and stretching or strengthening exercises can also often aid in relieving the pain. If your symptoms worsen or do not improve, make sure to seek medical attention.

Are you experiencing knee pain while bending down? At Flexogenix®, our board-certified physicians are dedicated to non-surgical solutions for knee and joint pain. Contact us today for a no-cost consultation and let us give you a personalized plan to relieve your pain and get you back to the active lifestyle that you deserve.

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