What Causes Stiff Knees? 9 Reasons, Their Telltale Signs, And Treatments

Written By on January 11, 2022 — Medically Reviewed By Kristopher Ceniza

Written by on January 11, 2022 — Medically Reviewed By: Kristopher Cenzia

Most of us have felt knee tightness at one point or another. But, what causes stiff knees in the first place?

There are at least 9 common conditions that cause knee stiffness. They range from something as harmless as lack of movement, to challenging conditions like arthrofibrosis.

But don’t worry – by the end of this article, you’ll know what may be the cause of your knee stiffness. And, more importantly, what to do about it.

Here’s what we’ll cover. Click on the condition to get there faster:

Let’s figure out why you experience knee stiffness, shall we?

9 causes of knee joint stiffness

1) Sedentarism

Yes, it can be as simple as this! Sometimes having a stiff or painful joint can be traced back to lack of movement.

See, movement keeps our joints healthy and flexible, while sedentarism makes them stiff and prone to knee pain.

This may be the cause of your knee stiffness if:

  • You don’t do much physical activity
  • Your knee stiffness worsens if you spend too much time in the same position
  • It gets better after you walk it off

What to do about it?

Following WHO’s guidelines on physical activity is enough for most adults. They recommend doing this every week (1):

  • At least 150–300 minutes of moderate-intensity activity. E.g. brisk walking, dancing, biking…
  • Strengthen all the major muscles at least twice a week
  • Add more movement during the day. E.g. climbing one flight of stairs daily

2) Ligament injury

Ligaments are strong bands of tissue that keep joints stable. We have four in each knee.

Now, when a knee ligament gets injured, our leg muscles have to get a bit tight. This restricts the movement of the knee, which helps the ligament heal.

Knee Force Knee Sleeve

So, it’s normal to feel some knee stiffness during this recovery process.

This may be the cause of your knee stiffness if:

  • You had a recent knee injury while playing running or contact sports
  • You feel knee instability
  • There was knee swelling in the first 24-48 hours after the injury
  • You twisted your knee recently
  • There was a popping sound on your knee at the moment of injury
  • You can’t bear weight on your knee

What to do about it?

Honestly, you don’t want to get rid of the stiffness during the first 1-4 weeks after injury. At least not completely, as it’s a protective response from your body.

This also means the tightness won’t improve unless the ligament heals. But, the good thing is that there are several things you can do to heal a knee sprain.

You can also try wearing a knee brace to relieve pain and boost your recovery process.

3) Meniscus tear

A meniscus is a C-shaped cartilage that acts as a shock absorber. We have two in each knee and they work with our ligaments to keep the knee stable.

Our leg muscles will also get stiff if a meniscus gets torn. It’s the same protective response that happens after a sprain.

This may be the cause of your knee stiffness if:

A meniscus tear can happen in the same circumstances and shares symptoms with a ligament injury:

  • Recent sports injury
  • Instability
  • A popping sound at the moment of injury
  • Joint pain
  • Your knee’s range of motion is impaired

Sometimes, meniscus injuries also involve mechanical problems. For example, you may feel the joint gets locked. (2)

What to do about it?

As with a ligament injury, knee stiffness is a protective response to help the meniscus heal. The tight muscles will relax once the injury recovers.

A meniscus can heal naturally, but some cases may need physical therapy or surgery. Wearing a knee brace can give you tons of relief during this process.

4) Runner’s knee

This refers to pain in the kneecap area. It’s also known as “patellofemoral pain syndrome” (PFPS) or “moviegoer’s knee.”

It’s one of the most common knee problems in active people – accounting for 25 to 40% of the knee problems seen in sports clinics. (3)

This may be the cause of your knee stiffness if:

  • You have knee pain around the kneecap
  • The knee feels stiff but you have full range of motion
  • Symptoms get worse with sitting, standing, and/or climbing stairs

What to do about it?

The causes and treatment of PFPS will vary from person to person.

For example, a runner with PFPS may need to improve his/her technique to get rid of the pain.

But an office worker may have a quadriceps muscle weakness that’s causing PFPS. So, she/he would have to do strengthening exercises to improve.

So, if you think you have PFPS, better go to a physical therapist in your area. They will assess your symptoms and give you individualized treatment.

5) Knee osteoarthritis

This is the wear and tear of the knee cartilage due to aging.

According to research, up to 43% of people over 40 years old have osteoarthritis with no symptoms whatsoever.

With that said, symptomatic knee osteoarthritis is a complex issue. Some patients have tons of physical limitations, while others feel mild pain and stiffness.

This may be the cause of your knee stiffness if you:

  • Are +40 years old
  • Had a previous knee injury, like a meniscus tear
  • Have a BMI >25
  • Your pain gets worse with rest and with movement
  • The knee pain wakes you up at night
  • Don’t remember injuring your knee recently

What to do about it?

Knee osteoarthritis can’t be reversed. But, there are several things you can do to delay the process.

Knee Force Knee Sleeve

For starters, if your BMI is above 25, losing weight is a great strategy. A 10% weight loss can do wonders for your knees. (4)

Also, work on strengthening your leg muscles. This will protect the remaining cartilage.

Yet, people with severe symptoms should consider a knee replacement.

Learn more: Our physio explains everything you should know about knee osteoarthritis

6) Rheumatoid arthritis (RA)

This is an autoimmune condition that involves swelling of the joints. Mostly the ones in the fingers, hands, and knees.

This may be the cause of your knee stiffness if you:

  • Have a family member with RA
  • Smoke cigarettes
  • Have a BMI >25
  • Are a woman
  • Feel morning stiffness
  • Have more than one joint affected at the same time

What to do about it?

This is a chronic disease, so seeking treatment is key to prevent knee arthritis complications.

Also, appropriate treatment can help manage arthritis pain and its flare-ups. This is mostly treated with medication and physical therapy.

7) Knee bursitis

Bursae are fluid-filled sacs that reduce friction between tissues, and “bursitis” is the inflammation of a bursa.

There are many types of knee joint bursitis, but most of them can cause severe pain and swelling – not only stiffness. Some can be infected as well.

This may be the cause of your knee stiffness if you:

  • Have a round, visible bump on your knee, often warm to the touch
  • Have a wound near a bursa – this can be a sign that the bursitis is infected
  • Kneel constantly due to your hobbies/job

What to do about it?

If you think you have knee bursitis, visit a doctor. You have to figure out whether it’s infected or not. Infected bursitis is treated with antibiotics, while non-infected bursitis has several treatment options.

8) Stiff knee syndrome

This joint condition is also known as “knee arthrofibrosis.” It’s when the body creates excessive scar tissue after knee surgery or an injury. (5)

This may be the cause of your knee stiffness if:

  • You’ve had a knee surgery recently
  • You haven’t done your post-surgical physical therapy properly
  • You have genetic predisposition
  • The surgeon didn’t perform the procedure correctly

What to do about it?

Arthrofibrosis is mostly treated with corticosteroid injections, physical therapy, and wearing knee braces to help with the pain. (5) However, some people will need surgery to remove the unnecessary scar tissue.

9) An underlying cause

Some diseases can also cause joint stiffness. Common examples include:

  • Septic arthritis
  • Gout
  • Fibromyalgia
  • Lyme disease
  • Psoriasis
  • Thyroid problems
  • A spine issue that’s referring symptoms to the knee

If you’re not sure what may be causing your symptoms, please visit a doctor.

This can help: Orthopedist vs Rheumatologist – which one should you visit?

How to alleviate knee stiffness at home?

First, it’s always better to have a healthcare professional identify the cause of knee stiffness. That makes sure you’ll get the right treatment.

But with that said, here are some things you can try to manage it:

PS: If you also have other symptoms like pain, instability, swelling, etc, please go to a doctor before trying anything at home. Otherwise, you risk worsening your symptoms.


Is walking good for stiff knees?

Yes! In fact, walking regularly can have protective effects on your knees. (6)

What causes stiff knee joints after sitting?

Being in the same position for a long period, lack of blood flow in the area. Take a 5-minute walking break every hour to prevent this.

When to see a doctor for a stiff knee?

If the stiffness happened after an injury and isn’t improving after 48 hours. Also, if you experience additional symptoms like:
– Redness, pain, and swelling around the joint.
– Knee instability.
– Can’t bend or straighten your knee fully.
– Fever.

Conclusion: Why does your knee joint feel stiff?

Knee stiffness can be your body’s way of asking for more movement. It can also be a protective response or a sign that something else is going on.

Make sure to identify the root cause first to find the best way to treat it!


  1. World Health Organization. Physical Activity. [26 November 2020]. Retrieved on December 2021 from: https://www.who.int/news-room/fact-sheets/detail/physical-activity
  2. Raj M A, Bubnis M A. Knee Meniscal Tears. [Updated 2021 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved on December 2021 from: https://www.ncbi.nlm.nih.gov/books/NBK431067/
  3. Bump J M, Lewis L. Patellofemoral Syndrome. [Updated 2021 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Retrieved on December 2021 from: https://www.ncbi.nlm.nih.gov/books/NBK557657/
  4. Messier, Stephen P et al. “Intentional Weight Loss in Overweight and Obese Patients With Knee Osteoarthritis: Is More Better?.” Arthritis care & research vol. 70,11 (2018): 1569-1575. DOI: 10.1002/acr.23608
  5. Usher, Kayley M et al. “Pathological mechanisms and therapeutic outlooks for arthrofibrosis.” Bone research vol. 7 9. 26 Mar. 2019, DOI: 10.1038/s41413-019-0047-x
  6. White, Daniel K et al. “Daily walking and the risk of incident functional limitation in knee osteoarthritis: an observational study.” Arthritis care & research vol. 66,9 (2014): 1328-36. DOI: 10.1002/acr.22362
  7. Evans J, Nielson JL. Anterior Cruciate Ligament Knee Injuries. [Updated 2021 Feb 19]. StatPearls. Retrieved on December 2021 from: https://www.ncbi.nlm.nih.gov/books/NBK499848/
  8. Chauhan K, Jandu J S, Goyal A, et al. Rheumatoid Arthritis. [Updated 2021 Oct 7]. Retrieved on December 2021 from: https://www.ncbi.nlm.nih.gov/books/NBK441999/
Mitch Torres (PT)
Mitch is a physical therapist, personal trainer, and nutrition coach. Fascinated with the knee joint, Mitch poured that passion into writing about knee pain and how to overcome it with movement. His goal is to teach you how to apply this knowledge into your daily life, so you can keep knee pain away for good.