It’s every athlete’s worst fear: you’re in the middle of a game, and you suddenly can’t move your leg without excruciating pain. You try to walk it off, but it gets worse. Finally, you have to admit defeat and call your coach to sub out because your knee hurts when straight but not when bent. And as you watch from the sidelines, you can’t help but wonder what’s wrong.

Is this a serious injury? Will I ever be able to play again?

Those questions can be daunting and can, at times greatly affect our confidence. However, the answers will vary. Pain in this joint can be caused by several knee problems which your doctor can discuss with you.

As you wait for your appointment, get a head start by understanding the common causes of knee pain and the treatment options available. We’ll first begin with the anatomy of the knee.

The Structure of Our Knees

As you may know, our knees are responsible for several daily activities we do.

The knee joint is one of the largest and most complex joints in the human body. It’s made up of the shin bone (tibia), the thigh bone (femur), and a small bone at the front of the knee (patella or knee cap).

The knee joint is held together by strong connective tissue, and a thin layer of fluid helps to reduce its friction. The meniscus, a layer of cartilage, protects the inside of the knee. They act as shock absorbers, absorbing impact when we walk, jump, or run.

The outside of the knee is covered by a layer of tough connective tissue called the fibrous capsule. This capsule helps to protect the knee from injury.

The knee is also surrounded by muscles, tendons, and ligaments that help to stabilize the joint and allow it to move smoothly. The quadriceps muscle group at the front of the thigh contracts to straighten the knee, while the hamstring muscle group at the back of the thigh contracts to bend the knee. The tendons and ligaments around the knee joint provide stabilizing support, helping to prevent dislocation.

Two crucial ligaments are the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL).

The ACL runs from the front of the knee to the back and helps to stabilize the joint. The ACL can be damaged by a sudden twisting force, such as when landing from a jump. This type of injury is particularly common in sports such as football and basketball.

The MCL runs down the side of the knee and helps to keep the joint stable. The MCL can be damaged by a direct blow to the side of the knee, or by twisting the knee too far to one side. This type of injury is less common than an ACL injury, but can still occur in sports such as football and soccer.


7 Reasons Your Knee Hurts When Straight But Not When Bent

Now that we’ve looked at the knee’s structure, let’s explore some of the most common reasons your knee might hurt when straight but not when bent.

Meniscus tear

The meniscus is a C-shaped piece of cartilage that acts as a cushion between your thighbone and shinbone. A torn meniscus can occur due to a sudden twisting motion or due to repetitive stress. Symptoms of a meniscus tear include severe pain, swelling, and stiffness.

Patellofemoral pain syndrome

Another common reason for knee pain is patellofemoral pain syndrome, also known as runner’s knee. This condition is caused by the wear and tear of the cartilage that surrounds the kneecap.

Symptoms include dull pain around the kneecap that gets worse when you walk downstairs or uphill. Runner’s knee is often seen in runners, hence the name, but it can also occur in non-runners who engage in activities that put stress on the knees, such as basketball or soccer.

Baker’s Cyst

A Baker’s cyst is a fluid-filled sac that forms behind the knee. It is often seen in people with arthritis, as the cyst forms when there is excessive joint fluid in the knee. Symptoms of a baker’s cyst include knee pain and stiffness, as well as swelling in the back of the knee.

Rheumatoid Arthritis

Rheumatoid arthritis is a form of chronic inflammation of the joints. It can cause pain, stiffness, and swelling in the knee joint. In severe cases, it can lead to deformity of the knee joint. Additionally, people with rheumatoid arthritis may experience fatigue and fever. 

ACL Tear

An ACL tear is a common ligament injury that can occur due to a sudden twisting motion. Symptoms of an ACL tear include knee pain and swelling, as well as instability of the knee joint.

An ACL tear can often be diagnosed with an MRI scan. To help relieve this type of pain, you may need to wear an elastic bandage, use crutches, or even get surgery.

Muscle Imbalances

Muscle imbalances around the knee can also cause knee pain. When the muscles surrounding the knee are not in alignment, it can put extra stress on the knee joint and lead to pain.

Muscle imbalances often occur due to tightness in certain muscle groups and weakness in others.

MCL tear

An MCL tear is less common than an ACL tear, but can still occur due to a direct blow or twisting motion. This type of ligament tear can include knee pain and swelling, as well as tenderness on the inside of the knee. An MCL tear can also often be diagnosed with an MRI scan.

Top 11 Treatment Options for Knee Problems

Physical Therapy

One of the best treatment options for knee problems is physical therapy. A physical therapist can help to stretch and strengthen the muscles around the knee, which can help to relieve pain. They can also help to realign the knee joint and improve your range of motion.


Exercising the muscles around the knee can help to alleviate knee pain. Strengthening exercises such as squats and lunges can help to support the knee joint. Flexibility exercises such as yoga and Pilates can also help to stretch the muscles around the knee and improve the range of motion.

Weight Loss

Carrying excess body weight can put additional strain on the knee joint, which can lead to pain. If you are overweight or obese, lose weight by dieting or doing the proper exercises. Make sure to consult your dietician and physical therapist first.

Anti-inflammatory Medications

Taking anti-inflammatory medications such as ibuprofen or naproxen can help to reduce knee swelling and pain. However, it is important to talk to your doctor before taking any medication, as they may have side effects.


In some cases, knee surgery may be necessary to repair a torn ligament or remove a cyst. However, knee surgery should only be considered as a last resort after other treatment options have been exhausted. Orthopedic surgeons have treated knee problems for a long time by realigning the knee.

Surgery usually involves cutting and repositioning the thighbone and then attaching it to the shinbone with screws and metal plates with grafts, or artificial parts depending on the condition being treated. The surgeon may also need to remove damaged cartilage.

Orthopedic surgeons generally confirm the necessity for surgery by having the patient undergo a physical exam and x-rays.


Resting the knee can help to reduce pain and swelling. Avoid activities that put additional strain on the knee joint, such as running or climbing stairs. Instead, focus on gentle exercises such as walking or swimming. After doing these activities, you should apply ice.

Cold or ice compress

Applying ice to the knee can help to reduce inflammation and pain. Ice or a cold pack should be applied for 15-20 minutes at a time, several times a day. Do not apply ice directly to the skin, as this could cause frostbite. Instead, wrap the ice in a towel or use an ice pack.

Heat Therapy

If you find that icing your knee is ineffective, you may want to try heat therapy instead. Applying heat to the knee can help to increase blood flow and relax tight muscles. Heat therapy can be done with a heating pad, hot water bottle, or warm compress.

Massage Therapy

Massage therapy can also help to reduce knee pain by improving blood circulation and relaxing the muscles around the knee. A massage therapist will use their hands to apply pressure and knead the muscles around the knee. Massage therapy should only be done by a professional.


Acupuncture is a form of traditional Chinese medicine that involves inserting thin needles into the skin. Acupuncture is thought to improve blood flow and relieve pain by releasing endorphins. Acupuncture also should only be done by a trained professional.

Knee brace and knee cap

Knee braces are often used to provide support and stability for the knee joint, which can help to reduce pain and swelling. Wearing a knee brace is another popular treatment option for knee problems. They are designed to protect the knee joint from impact and allow for a greater range of motion.

These are just some of the many treatment options available for knee problems. Talk to your doctor about which option is best for you.


Trust the Process

Knee problems can be frustrating, and it can be tempting to give up in the face of setbacks. However, it’s important to trust the process and be patient. Knee surgery is a serious procedure, and it takes time to recover. Remember, everyone heals at their own pace.

Some people may see a dramatic improvement in their symptoms immediately after surgery, while others may take months or even years to see a noticeable difference. Knee surgery is not a quick fix, but it can be a very effective treatment for long-term knee problems. Just be sure to listen to your body and don’t be too hard on yourself as you heal.

About the Author

Hi there! I’m Dr. Keagen Hadley, OTD, OTR/L. Straight out of the University of Mary, I’m all about blending my know-how in knee health, well-being, and medical technology. As a licensed occupational therapy doc, I’m here to translate complex concepts into clear, actionable insights – whether it’s knee care or groundbreaking healthcare tech.

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