3 Rehabilitation Exercises for Knee Stiffness

Identify relevant exercises based on whether your knee is stiff in flexion or extension

Your knee may have difficulty primarily in one of these two positions:

1️⃣ Your knee may struggle to bend completely.

In this case, you have limited knee flexion.

A “normal” knee flexion is typically between 135° and 150° (or more).

For activities like cycling, a minimum of 100-120° of knee flexion is generally required. The same goes for getting into a car or comfortably using stairs.

2️⃣ Your knee may have difficulty fully straightening.

In this case, you have limited knee extension.

Normal knee extension is 0°, possibly up to 10° of hyperextension.

Limited knee extension can affect many sports activities as well as everyday walking.

3️⃣ Your knee may also be stiff and limited in BOTH FLEXION and EXTENSION.

In this case, you will need to implement strategies to regain both of these movements.

Measure where you stand!

There are free applications that can more accurately measure the flexion and extension of your knee. I personally use Angulus Classic.

Why can this be beneficial?

✅ Because it can be more motivating to objectively measure your progress.

And potentially stop (or change) your exercises if you don’t see any improvement after, for example, a month of daily practice.

Here’s what it looks like:

To do this, you need to:

• Download the free Angulus app.
• Open the app.
• Take a photo in the app of your knee profile with maximum flexion (have someone take it for you), on the outside of your leg.
• Place the red circle in the middle of the knee, and the ends of the lines on the outer ankle bone (malleolus) and along the femur, in the middle of the hip.
• To know your knee flexion, you need to calculate 180-110.3° (displayed in red) = 69.7°.

🚨 Always position yourself in the same way to track the evolution of your knee flexion.

Otherwise, you won’t be able to compare the progress of your measurements, as flexion can vary greatly depending on your setup (e.g., hip more or less flexed).

What precautions should you take before doing exercises?

For each exercise, it’s normal to feel some discomfort. However, there are 4 conditions to respect for everything to go smoothly:

🟢 You do not have any contraindication to take your knee into flexion or extension (for example, following a patellar fracture, knee flexion is often limited to a maximum of 90° for a few weeks).

🟢 The pain should be tolerable and not make you grimace. If it does, reduce the range of motion or speed of movement.

🟢 Each time you return to the starting position during the exercise, the pain should either immediately disappear or return to its initial level (if you were already in pain at the beginning).

🟢 The pain you feel during the exercise should remain consistent with each repetition. It should not increase with each repetition.

If these conditions are not met, try:

• Reducing the range of motion (go a little less forward, backward, etc.).
• Slowing down the movement.
• Doing fewer repetitions (started with 10 repetitions? Try doing only 6, for example).

Note that all the principles above are equally applicable if you are taking pain relievers.

Normally, the exercises I present next are suitable for everyone, provided you find the right dosage.

If you encounter difficulties, don’t hesitate to seek direct assistance from your physical therapist.

Exercise to regain knee extension

This exercise helps regain knee extension, allowing your knee to fully straighten.

➡️ Equipment needed: Two chairs

➡️ Starting position: Sit on one chair. Place the foot of the stiff leg on the other chair, with the knee hanging freely.

➡️ Instructions: Gently press your knee with your hands to assist in fully straightening it.

🔸 Easier and more comfortable variation 🔸

If this is too painful or uncomfortable, position the chair closer to reduce the unsupported knee hang.

Also, place a cushion under your leg to relieve discomfort.

➡️ Work quantity: Aim for 1 to 2 times per day minimum, ideally daily.

Maintain the position for at least 1 to 2 minutes initially, then increase to 10 or even 20 minutes.

If the pain is too significant, try reducing the range of motion. In other words, apply less pressure on the knee or try the variation below.

➡️ Why this exercise?

The knee is hanging freely, making it easier to extend. Additionally, in this position, gravity naturally assists in straightening your knee.

Sitting places your hip in flexion, increasing tension on the muscles behind the leg (hamstrings). This helps stretch these muscles, which may partly be responsible for the lack of flexibility in your knee.

2 exercises to regain knee flexion

The goal of these exercises is to regain knee flexion: to allow the knee to bend completely.

Exercise 1: Standing with a chair

➡️ Equipment needed: a chair

➡️ Starting position: stand with the foot of the stiff leg on a chair. The higher the chair, the more difficult the exercise and the more knee flexion required.

➡️ Instructions: Shift your body weight forward to bend the knee further.

🔸 Easier variation 🔸

Choose a lower chair, stool, or step to reduce the amount of knee flexion.

➡️ Work quantity: Aim for 1 to 2 times per day minimum, ideally daily.

Hold the position for 30 seconds to start, then increase to 1 to 2 minutes.

If the pain is too significant, try reducing the range of motion. In other words, do not bend the knee as far forward.

➡️ Why this exercise? Gravity assists in bending the knee further in this position. Being standing allows you to apply more weight and facilitate flexion.

Lastly, standing puts your hip in flexion, which helps in knee flexion by stretching the quadriceps muscle less, which can limit knee flexion.

Exercise 2: Lying on your stomach

➡️ Equipment needed: something to lie down on + (a belt, elastic band, or strap)

➡️ Starting position: lying on your stomach.

➡️ Instructions: Bring the foot of the stiff knee side as close to your buttocks as possible. Use your hand to assist in bringing your foot closer. Keep your knee in contact with the surface you are lying on; do not lift it off.

🔸 Easier variation 🔸

If you are unable to reach your foot with your hands, use a strap or belt to pull your leg towards you.

➡️ Work quantity: Aim for 1 to 2 times per day minimum, ideally daily.

Hold the position for at least 1 to 2 minutes to start, then gradually increase to 10 or even 20 minutes.

If the pain is too significant, try reducing the range of motion. In other words, put less pressure on the knee by using the variation below.

➡️ Why this exercise?

Being on your stomach places your hip in extension. When you bend your knee, it stretches your quadriceps muscle.

Stretching the quadriceps is beneficial as it can partly contribute to your knee stiffness.

It’s normal to have less flexion in this position compared to when your hip is flexed.

Can exercises really improve knee stiffness?

Most studies evaluating the effectiveness of knee exercises primarily focus on their ability to relieve pain or improve functional scores. Few studies assess the gain in range of motion in flexion or extension as a primary outcome.

Furthermore, the results of these studies vary depending on the underlying cause of the stiffness, such as:

• total knee replacement,
• unexplained knee Complex Regional Pain Syndrom,
• patellar fracture,
• knee osteoarthritis [Mo 2023], etc.

To understand the specific effectiveness of exercises, I encourage you to explore other articles on this site, whether they are current or forthcoming!

In general, testing daily knee flexibility exercises for a month seems worthwhile, provided there are no contraindications and the exercises are not too painful.