Why does my knee hurt when I bend it?

Written & Medically Reviewed by Dr. Chinmay Gupte 

Consultant Orthopaedic Surgeon | Clinical Reader in Knee & Trauma Surgery, Imperial College London

Do you ever feel pain in your knee when sitting down, climbing stairs, or squatting? You’re not alone. Knee pain is one of the most common problems people experience, whether from daily wear and tear, sports, or simply aging. For many, bending the knee can turn into a frustrating and uncomfortable challenge.

This guide is designed to help patients, families, and caregivers understand why knee pain happens, what symptoms to watch for, and the treatments and lifestyle changes that can make everyday life easier and more mobile.

  Common Symptoms Patients Notice

Knee pain can present in different ways. Some of the most frequent complaints include:

 ●     Sharp pain in the front areas of the knee (especially while squatting or climbing stairs).

●     Clicking or popping sounds when bending.

●     Stiffness and reduced flexibility in the knee.

●     Swelling or inflammation around the knee.

●     Pain that worsens after sitting for long periods

●     A feeling that the knee might “give out” or slip

6 Common Reasons for Knee Pain When Bending

Several conditions can cause pain when you bend your knee. The most common include:

 1. Patellofemoral Pain Syndrome (Runner’s Knee)

Occurs when the kneecap (patella) doesn’t move smoothly in its groove. This is common in athletes and people who sit for long hours.

2. Meniscus Tear

The meniscus is a piece of cartilage that cushions the knee. A sudden twist or awkward movement can tear it, leading to pain, swelling, or the knee “locking up.”

3. Arthritis

Both osteoarthritis, characterised by joint wear and tear, and rheumatoid arthritis, an autoimmune condition that can affect the knee, can make bending painful by stressing already inflamed joints

.4. Tendonitis (Jumper’s Knee)

Inflammation of the tendons, especially the patellar tendon, often causes pain during bending or squatting. This is common among athletes who jump frequently.

.5. Ligament Injuries

Injuries to ligaments in the knee, such as the ACL or MCL, can cause pain, swelling, and instability, often triggered by sports or sudden twisting

 6. Bursitis

The knee has small fluid-filled sacs called bursae that reduce friction. When these become irritated or inflamed, they can cause swelling, tenderness, and pain when bending.

 How Doctors Diagnose Knee Pain?

Your doctor will first ask about your symptoms and overall medical history, followed by a physical examination. Depending on what they find, further tests may include:

X-rays –To check bone alignment and signs of arthritis

MRI scans –To detect ligament or meniscus injuries

Ultrasound –To examine soft tissues and inflammation

Lab tests –To rule out infections or autoimmune conditions

 Treatment Options for Pain on Bending the Knee

The right treatment depends on the cause and severity of your pain. Options include:

 ●     Non-Surgical Treatments:

If your knee pain is mild, these non-surgical treatments may help relieve discomfort and restore normal function

 Rest and Activity Modification –Avoid movements that aggravate pain and allow the joint to heal

.Physiotherapy –Targeted exercises can strengthen muscles, improve flexibility, and reduce strain.

Pain Relief Medications –Over-the-counter options such as paracetamol for pain relief or anti-inflammatorymedications like ibuprofen for both pain and swelling can help manage symptoms. Always use them as directed by your doctor

 Injections –Hyaluronic acid or corticosteroid injections may relieve inflammation and lubricate the joint.

 ●     Surgical Treatment Options:

If non-surgical or conservative care doesn’t work out, surgery can be suggested, like:

 Arthroscopy –A minimally invasive “keyhole” procedure to repair or remove damaged tissue.

Ligament Reconstruction –Restores stability by replacing or repairing torn ligaments with grafts.

Partial or Total Knee Replacement –Recommended for advanced arthritis to restore mobility and reduce pain.

 Top Notch Home Care & Preventive Tips

Simple steps can make a big difference in protecting your knees:

 ●     Maintain a healthy body weight to reduce stress on the joints.

●     Choose low-impact exercises like swimming or cycling. This will strengthen your muscles and improve mobility.

●     Stretch regularly to improve flexibility

●     Avoid deep squats or sudden twisting movements if they cause pain.

●     Apply ice packs after activity to reduce swelling.

 When Should You See a Doctor?

Must seek medical help if:

 ●     The pain continues for more than a few weeks.

●     You notice significant swelling or redness around the knee.

●     Your knee often locks, catches, or feels unstable.

●     You cannot comfortably put weight on the affected leg.

 Prompt diagnosis and treatmentreduces the chance of long-term damage.

The Good News

Knee pain when bending is very common, but in most cases, it can be managed with the right combination of lifestyle changes, physiotherapy, and if necessary, minimally invasive treatments. With proper care, mobility and comfort can often be restored.

 Frequently Asked Questions (FAQs)

Why does my knee hurt only when I squat?

Squatting places extra pressure on the kneecap and meniscus, which can reveal cartilage or ligament problems.

 Can knee pain improve without surgery?

In short: Yes, but it depends on the cause. Many conditions, like mild tendonitis, often improve with rest, physiotherapy, and lifestyle adjustments.

 Is knee pain while bending serious?

Not always, but ongoing or worsening pain should not be ignored, it may signal cartilage or ligament damage.

 Can I exercise if my knee hurts while bending?

Low-impact activities are usually safe, but always consult a doctor before continuing exercise.

 When should I see a doctor for knee pain while bending?

If pain persists, limits mobility, or affects daily life, it’s time to see a doctor for diagnosis and treatment.

About Author

Dr. Chinmay Gupte is a Consultant Orthopaedic Surgeon and Clinical Reader (Associate Professor) in knee and trauma surgery at Imperial College London, working across St Mary’s and Charing Cross Hospitals. He also leads the Wellington Knee Unit at the Platinum Medical Centre, the UK’s first dedicated knee clinic.

As an ex-professional sportsman, Dr. Gupte was awarded the first-ever surgical PhD in knee ligament research by Imperial College London, giving him unique expertise in both sports-related and complex knee conditions.

With over two decades of experience, his specialist areas include:

Meniscus injuries and repair

ACL injuries and reconstruction (including paediatric ACLs)

Patellofemoral instability

Knee arthritis (injections, resurfacing, and replacements)

Robotic knee replacement surgery

Osteochondral and complex sports knee injuries

Multiple ligament injuries and knee dislocations

Dr. Gupte is an Executive member, trustee, and treasurer of the British Association for Surgery of the Knee (BASK), and has served on committees at the British Orthopaedic Association and Royal College of Surgeons of England. His research and teaching at Imperial College focus on cutting-edge treatments like meniscal preservation, paediatric ACL surgery, and non-surgical alternatives for osteoarthritis.

He has won multiple awards, including the British Orthopaedic Association Robert Jones Medal and the Royal Society of Medicine President’s Medal, and continues to train the next generation of orthopaedic surgeons.

Dr. Gupte is committed to a patient-first, multidisciplinary approach, combining advanced technology with tried-and-tested methods to deliver safe, effective, and tailored treatments for every patient.