How to Start Working Out Again After a Knee Injury

If you’re wondering how to start working out again after a knee injury, you’re not alone. Knee injuries are incredibly common – about 41% of all sports injuries involve the knee (1) – and even outside of sports, knee pain affects nearly one-quarter of adults (2). Many people have been in your shoes, itching to get active but nervous about re-injury or setbacks.

The good news is that with the right game plan – grounded in physical therapy wisdom and real-life fitness know-how – you can safely return to working out. This isn’t about pushing through pain or pretending the injury never happened. It’s about making a smart, gradual comeback: rebuilding strength, protecting your knee, and regaining confidence step by step.

This guide will walk you through practical tips to ease back into exercise after a knee injury. From gentle mobility moves and knee-friendly workouts to strategies for pacing yourself, consider this a road map for getting fit again without wrecking your knee in the process. Let’s dive in (carefully) and get you moving on the path to recovery.

First Things First: Get the Green Light

Before you jump back into workouts, make sure you have the all-clear from your doctor or physical therapist. This means your knee has healed enough – any major pain, swelling, or stiffness should be greatly improved.(3) If those symptoms are still lingering, pushing yourself too soon could delay recovery or even make your injury worse. (4) So get that professional thumbs-up and follow any specific guidance they give you.

Equally important is adjusting your mindset. It’s completely normal to feel nervous about exercising again (fear of re-injury is common), but remember that your injury is temporary and you will get back to the activities you love – it just takes time. (5) Your first workouts won’t be at your old intensity, and that’s okay. Think of yourself as being in “rehab training” mode. The goal is to ease in safely, not set any personal records right away.

One tip: start slower than you think you need to. It’s better to under-do it at first than overdo it. As orthopedic experts often say, patience now will pay off later – rushing leads to setbacks or re-injury. (6) So, take a deep breath and be prepared to go slowly. You’re cleared for takeoff, but we’ll taxi on the runway before we fly.

Ease In with Mobility and Stretching

After a knee injury, your motto should be “crawl before you walk.” In other words, ease your knee back into motion gradually. Start by focusing on basic mobility (how well your knee bends and straightens) and flexibility in the muscles around it.

Warm up first: Before any workout – even a light one – give your knee a gentle warm-up. Do about 5-10 minutes of easy, low-impact activity like brisk walking or riding a stationary bike. (7) This increases blood flow, loosens your joint, and helps prevent injury.

Next, do some gentle stretching to restore range of motion. For example, slow knee bends and straightens, heel slides (lying on your back, sliding your heel toward your butt), or calf and quad stretches. Stretching the muscles around the knee helps relieve stiffness and improves flexibility, which protects you from further injury. (8) Aim to stretch daily, holding each stretch for 20-30 seconds. Keep it gentle – you should feel a mild pull, not pain. (9) If any stretch causes sharp pain, stop.

Remember, exercises should not cause sharp pain – if something hurts beyond mild discomfort, ease off. (10) By improving your knee’s flexibility and mobility, you’re laying the groundwork for the tougher exercises to come.

Low-Impact Cardio: Get Your Heart Pumping (Gently)

Once your knee has a bit of mobility back, you can reintroduce cardio – but stick to low-impact activities at first. These will get your blood pumping without jarring your recovering knee.

Walking: One Step at a Time

Walking is an excellent way to start. It’s simple, functional, and low-impact. Begin with short, flat walks – even 10 minutes – and see how your knee feels. If that’s fine, you can gradually increase your distance or pace over time. Doctors often encourage walking as soon as it’s comfortable because it helps maintain leg strength and circulation without undue stress. (11)

As you walk, pay attention to your form. Try not to limp or favor your uninjured side. If you find yourself hobbling, slow down and shorten your stride. It’s okay to take it slow – the important part is that you’re moving and testing your knee in a controlled way.

Pool Workouts: Swimming and Water Therapy

If you have access to a pool, take advantage of it. Water exercise is incredibly gentle on the joints. The water’s buoyancy means your knee only bears a fraction of your body weight, allowing you to move with much less pain or impact. (12)

Try swimming or simply walking in the shallow end. You can also join a water aerobics class or do exercises like leg swings and mini-squats in the pool. The resistance of the water helps you rebuild strength and range of motion without the joint stress of land exercise. Aquatic therapy is a staple in many knee rehab programs for this very reason.

Just be mindful to avoid any pool movements that cause pain, but chances are you’ll find the water a welcome relief for your knee.

Cycling: Pedal with Caution

Cycling (especially on a stationary bike) is another knee-friendly cardio exercise. It keeps your knee moving in a controlled, non-impact way. Start with an easy spin – low resistance, gentle motion for 5-10 minutes. Make sure the bike seat is high enough that your knee is only slightly bent at the bottom of the pedal stroke (to avoid too much bend).

Orthopedic experts often recommend stationary biking to help rebuild knee strength and endurance after injury. (13) As your knee tolerates it, you can slowly increase the time or add a bit of resistance. If you go outdoors on a bicycle, stick to flat terrain and a comfortable pace.

The rule here (as always) is no pain. You might feel your muscles working, but if your knee joint hurts, stop. Cycling should feel smooth on the knee. Many people find it actually loosens up a stiff knee and boosts their confidence in using that leg again.

Strength Training: Build Your Knee’s Support System

To protect your knee and regain full function, you need to strengthen the muscles around the joint. Think of your leg muscles as shock absorbers – if they’re strong, they take pressure off your knee. (14) It’s common to lose muscle after a knee injury (studies show you can lose up to one-third of your quad strength after an ACL tear (15)), so rebuilding those muscles is crucial.

Focus on the major muscle groups:

• Quadriceps (front of thigh): e.g. straight-leg raises or mini-squats (only go as low as comfortable).
• Hamstrings and Glutes (back of thigh and butt): e.g. glute bridges or hamstring curls (using a resistance band or machine).
• Hips (outer thighs and glutes): e.g. side-lying leg lifts or clamshells with a small resistance band.

Aim to do these strength exercises about 2-3 times per week. Start with just your body weight or very light resistance. The goal is to wake the muscles up and build endurance. Ensure you use good form and avoid any movement that causes knee pain. For instance, if a full squat hurts, do a half squat or try sit-to-stand from a chair instead.

Don’t neglect your calves and core either – calf raises will strengthen your lower legs, and core exercises (planks, etc.) will help stabilize your body. Strong hips and abdominals help keep your knee aligned properly during movement, reducing strain on the joint. (16)

As you get stronger, you can gradually increase the resistance (heavier weights or tighter bands). But keep your progression slow and controlled. Each bit of strength you build in your legs is added protection for your knee. After a few weeks of consistent strength work, you’ll likely notice everyday activities (climbing stairs, standing up from a chair) getting easier – a sure sign that your muscles are supporting your knee better.

Progress Gradually and Mix It Up

When you feel your baseline strength and cardio improving, resist the temptation to jump straight into high intensity. Follow the “slow and steady” approach. A common guideline is the 10% rule – increase your activity by no more than about 10% per week. (17) For example, if you’re comfortably walking 20 minutes, add just 2-3 minutes next week, not 20.

In practical terms, start at around half of your pre-injury workout level and build up from there. (18) If you used to run 5 miles, you might begin with a 2-mile walk or a walk/jog combo, then gradually increase distance or speed over several weeks. (19) Always listen to your knee: if it handles a workout with no pain or swelling, you can inch it up a bit next time. If not, give yourself more time at the current level.

Avoid doing too much too soon. Also, avoid pounding your knee every day. It’s important to alternate harder workouts with lighter ones (or rest days). For instance, do a bike ride or leg workout one day, and focus on your upper body or take a rest the next. Cross-training in this way keeps you fit while giving your knee time to recover between sessions. (20) And don’t skip rest days – that’s when your body heals and gets stronger.

This phase requires patience. You might feel like you could do more, but it’s wiser to ramp up slowly than risk a setback. Consistent, gradual progress will get you to your goals faster in the long run, because you won’t be knocked off track by an angry knee. Trust the process and give your knee time to adapt.

Listen to Your Body: Pain vs. Progress

Your knee will usually tell you if you’re doing too much. Learn to distinguish normal soreness from problematic pain. It’s okay to have a bit of muscle soreness or achy tightness around the knee after exercise – that’s normal as you get back in shape. But sharp pain in the joint, significant swelling, or feelings of instability are warnings to slow down or stop. (21)

A good rule: you should not have pain above a mild discomfort during exercise, and any fatigue or achiness should resolve shortly after. If you experience pain that is more than a minor niggle, or if your knee is throbbing or swollen for hours after a workout, take that as a sign you overdid it. (22) Back off and rest for a day or two, then resume at a gentler level.

Never try to “push through” serious knee pain. That approach can turn a minor issue into a major setback. Instead, use tools like ice and elevation if your knee is sore, give yourself an extra rest day, and then continue with your plan at a lighter intensity. It’s all about finding the sweet spot where you’re challenging yourself but not causing harm.

In short: pain is your body’s way of keeping you safe. Respect it. Over time, as your knee gets stronger, you’ll be able to do more and more without pain – but always stay mindful of what your body is telling you.

Recap: Your Knee Comeback Cheat Sheet

• Clear it with your doctor: Don’t start exercising until a medical professional says you’re ready. Skipping this step can lead to setbacks. (23)
• Start with mobility and flexibility: Warm up every time, and do gentle stretches or PT exercises daily to get your knee moving freely.
• Stick to low-impact cardio: Favor walking, cycling, or swimming over running and jumping at first. These activities get you fit without pounding your knee. (24)(25)
• Strengthen your leg muscles: Build strength in your quads, hamstrings, glutes, and hips. Strong muscles support the knee and absorb shock. (26) Use light resistance and good form.
• Increase gradually: Add intensity or duration in small increments (around 10% per week) as long as your knee feels good. (27) Patience prevents re-injury.
• Watch for pain: Mild muscle soreness is okay, but sharp knee pain or swelling means stop and rest. (28) Never push through serious pain.

Returning to exercise after a knee injury takes time, but each step (literally) brings you closer to your old self. By being smart and listening to your body, you’ll build strength and confidence day by day. Soon enough, you’ll be doing more and worrying less. Stay patient and consistent – you’ve got this!