8 Exercises to Strengthen Knees with Arthritis (That Physical Therapists Actually Use)

Strengthening the muscles around the knee is the single most evidence-backed intervention for knee osteoarthritis pain — stronger quadriceps and hip abductors reduce the load on the joint with every step, improving pain and function more durably than most passive treatments. These 8 exercises are drawn from physical therapy protocols for mild-to-moderate knee arthritis and are appropriate for adults over 40 who have been cleared for light exercise. Start with the earlier exercises and progress only when you can complete them comfortably for two sets.

This content is educational and not medical advice. If you have moderate-to-severe knee arthritis, have had knee surgery, or are experiencing acute pain or swelling, consult a healthcare provider or physical therapist before starting a strengthening program. Stop any exercise that causes sharp, joint-level pain during the movement itself (mild muscle fatigue is expected and normal).

Table of Contents

• Why Strengthening Works for Knee Arthritis
• Before You Start: Key Safety Rules
• The 8 Exercises
• How to Structure a Weekly Program
• When to Wear Support During Exercise
• Frequently Asked Questions

Why Strengthening Works for Knee Arthritis

The knee joint itself has no muscles crossing it that are designed to hold the joint in place — stability comes from the muscles above and below it. The quadriceps (front of the thigh) control how the knee absorbs impact during each step. The hamstrings (back of thigh) control deceleration and rotational stability. The hip abductors (gluteus medius, outer hip) control valgus stress — the inward collapse that places the most damaging load on the medial knee compartment.

In adults with knee arthritis, quadriceps strength is typically 20–40% lower than in age-matched adults without arthritis. This weakness is partly a cause and partly a consequence of the pain — the knee hurts, so the person moves less, which causes further muscle atrophy, which puts more direct load on the damaged joint, which increases pain. Strengthening interrupts this cycle.

A 2015 systematic review in Arthritis Care and Research analyzing 54 randomized controlled trials found that land-based exercise produced statistically significant improvements in pain, physical function, and quality of life for knee osteoarthritis — with effect sizes comparable to non-steroidal anti-inflammatory medications in the short term, and significantly better long-term durability. The exercises that showed the largest effects were those targeting quadriceps and hip muscles specifically.

Before You Start: Key Safety Rules

• Distinguish between muscle soreness and joint pain. Mild aching in the thigh muscles 24–48 hours after exercise (delayed onset muscle soreness) is normal and expected. Pain inside the joint during exercise — sharp, stabbing, or a deep aching right at the knee — is a signal to reduce load or range of motion.
• Start in a pain-free or near-pain-free range. Most of these exercises can be modified to reduce range of motion if the full range causes discomfort. A shorter range performed correctly is far more beneficial than a full range that creates compensation patterns.
• Use a chair or wall for balance support. Balance challenge should not be the limiting factor when the goal is building strength. Lean on a wall or hold a sturdy chair so muscle fatigue — not stability — determines your effort.
• Two sets of 10–15 reps is the starting target. Begin with one set if needed. Progress by adding a third set before increasing resistance or difficulty.

The 8 Exercises

1. Seated Leg Extension

Targets: Quadriceps (primary)

How to do it: Sit in a chair with feet flat on the floor. Slowly straighten one leg, extending the knee until it is fully extended. Hold for 2–3 seconds, then lower slowly. Alternate legs.

Modification: If full extension is painful, straighten to the point of mild discomfort and hold there. Even a partial range strengthens the quadriceps through the available arc.

Why it matters: The seated position removes bodyweight load from the knee entirely, allowing quadriceps activation without joint compression — ideal for acute flare days or when the knee is more sensitive than usual.

Start with: 2 sets × 12 reps per leg

2. Straight Leg Raise

Targets: Quadriceps (especially the VMO — the teardrop-shaped inner quad that supports patellar tracking)

How to do it: Lie on your back with one knee bent and that foot flat on the floor. Keep the opposite leg straight. Tighten the thigh of the straight leg and raise it to the height of the bent knee. Hold 2 seconds. Lower slowly. Complete all reps on one side before switching.

Why it matters: Zero knee joint loading — the knee stays straight throughout. Directly targets the VMO, which is critical for patellar tracking and reducing anterior knee pain.

Start with: 2 sets × 12 reps per leg

3. Standing Hip Abduction

Targets: Gluteus medius, hip abductors (the outer hip muscles that control valgus knee stress)

How to do it: Stand next to a wall and hold it lightly for balance. Stand on one leg and lift the other leg outward to the side — about 30–40 degrees. Avoid leaning your torso to the side. Hold 2 seconds at the top, lower slowly.

Why it matters: Weak hip abductors allow the knee to collapse inward during walking, increasing medial compartment stress. This exercise directly addresses the most common movement fault in adults with medial knee arthritis.

Start with: 2 sets × 12 reps per leg

4. Mini Squat (Partial Squat)

Targets: Quadriceps, glutes, hamstrings (functional, weight-bearing)

How to do it: Stand with feet shoulder-width apart, holding a chair back for balance. Slowly lower as if you are about to sit, going only to about 20–30 degrees of knee bend (not a full squat). Keep knees tracking over toes — not caving inward. Return to standing. This should feel like the beginning of sitting down, not a deep squat.

Why it matters: Partial squats build functional quad and glute strength in the range used for everyday activities (getting up from a chair, climbing stairs) without the joint compression of a deep squat.

Start with: 2 sets × 10 reps

5. Step-Up

Targets: Quadriceps, glutes — functional loading in a single-leg pattern

How to do it: Place one foot on a step (start with a low step — 4 to 6 inches). Slowly push through that heel to step up, bringing the other foot to join it. Step back down leading with the same foot. Do all reps on one side before switching. Use a handrail for safety.

Why it matters: Step-ups replicate stair climbing and transitioning between surfaces — some of the most common pain-provoking activities for adults with knee arthritis. Building strength in this specific movement pattern reduces pain during the movement itself.

Start with: 2 sets × 8 reps per leg

6. Calf Raise

Targets: Gastrocnemius and soleus (calves) — relevant because calf weakness contributes to poor shock absorption at the ankle, which increases knee stress

How to do it: Stand behind a chair and hold it lightly. Rise up onto your toes, hold 2 seconds, lower slowly. If single-leg is comfortable, progress to one leg at a time.

Why it matters: The calf muscles work with the knee extensors to absorb impact during walking. Weak calves shift more impact load to the knee. Often overlooked in knee rehabilitation programs, but a consistent feature of physical therapy protocols for knee osteoarthritis.

Start with: 2 sets × 12 reps

7. Supine Bridge (Glute Bridge)

Targets: Glutes, hamstrings, core — posterior chain support for the knee

How to do it: Lie on your back, knees bent, feet flat on the floor hip-width apart. Press your heels into the floor and lift your hips until your body forms a straight line from shoulders to knees. Hold 2–3 seconds at the top, lower slowly.

Why it matters: Strong glutes reduce the anterior pelvic tilt and hip internal rotation patterns that increase valgus knee stress. The bridge is one of the most well-tolerated glute exercises for people with knee pain because the knee is static during the movement.

Start with: 2 sets × 12 reps

8. Terminal Knee Extension (TKE) with Resistance Band

Targets: VMO (inner quadriceps), the final 30 degrees of knee extension — the range most commonly weak in knee arthritis

How to do it: Anchor a resistance band around a fixed object at knee height. Stand with the band looped behind your knee. Step back to create slight tension in the band. The band will pull the knee forward slightly. Tighten your thigh muscle and straighten the knee against the band resistance. Hold 2 seconds, release slowly. The range of motion is small — just the last 30 degrees of extension.

Why it matters: The VMO (vastus medialis oblique) is the first quadriceps head to atrophy in knee arthritis and the critical muscle for patellar tracking and terminal extension strength. TKEs directly target this range in a weight-bearing position without stressing the joint at deep angles.

Start with: 2 sets × 12 reps per leg (light resistance band)

How to Structure a Weekly Program

Physical therapy guidelines for knee osteoarthritis recommend strengthening 2–3 times per week, with at least one rest day between sessions. Muscles adapt during rest, not during exercise — too frequent loading without recovery leads to fatigue-related compensation rather than strength gains.

A practical starting schedule:

• Week 1–2 (Foundation): Exercises 1, 2, 3, 7 — two sets each, 2x per week. Focus on form and range of motion.
• Week 3–4 (Building): Add exercises 4, 5, 6 — still two sets, 3x per week.
• Week 5+ (Progression): Add exercise 8 (TKE), increase to 3 sets, begin adding light resistance where indicated.

Expect mild muscle soreness in the thighs, hips, and calves in the first 2 weeks — this is normal adaptive soreness and should resolve within 48 hours. If you are still sore on day 3 or 4, reduce volume and allow more recovery before the next session.

When to Wear Support During Exercise

A knee compression sleeve worn during exercise provides proprioceptive feedback and warmth that can reduce discomfort during loaded movements. It does not provide structural support for instability but does improve the joint’s sensory accuracy — which can meaningfully improve how movements feel, especially in the early weeks before strength gains reduce pain independently.

If you are using a sleeve during exercise, the Wellnee compression sleeve is designed for active use and includes a patellar ring that supports tracking during exercises like step-ups and mini squats. For more significant instability, a structured brace may be more appropriate — the differences are covered in the sleeve vs brace guide.

Remove support garments during rest and after your session — the goal is to progressively require less external support as the muscles strengthen around the joint.

Frequently Asked Questions

Is exercise safe with knee arthritis?

Yes — for most people with mild-to-moderate knee osteoarthritis, appropriately dosed exercise is not only safe but is the treatment most consistently recommended by rheumatology and orthopedic guidelines. The concern about “wearing out the cartilage” with exercise is not supported by research. Weight-bearing exercise (when done correctly) actually supports cartilage nutrition through the compression-and-release mechanism that delivers nutrients to cartilage tissue, which has no blood supply of its own.

What exercises should I avoid with knee arthritis?

High-impact activities (running on hard surfaces, jumping, deep pivoting sports) should be modified or avoided if they consistently produce joint-level pain during or after activity. Deep full squats past 90 degrees of knee bend generate high patellofemoral compressive forces and are typically uncomfortable for people with kneecap arthritis or patellofemoral syndrome. Long-distance walking on very hard surfaces without adequate footwear or rest breaks may exacerbate symptoms. The key principle is: if an activity causes sharp joint pain during the activity or causes significantly worsened swelling and pain that persists for more than a few hours after, it is exceeding your current tolerance — reduce intensity rather than stopping entirely.

How quickly will I see results?

Most people notice improved ease of everyday movements (getting up from chairs, stairs) within 4–6 weeks of consistent 2–3x/week strengthening. Measurable strength improvements on testing typically appear at 6–8 weeks. Pain reduction following from those strength gains may take 8–12 weeks to become significant, particularly for chronic arthritis. The trajectory is positive but requires patience — strength rebuilding after years of atrophy is real but not instant.

Should I exercise when my knee is swollen?

Mild chronic swelling (the kind that has been present for months as a baseline) is not a reason to stop gentle exercise, particularly seated and lying-down exercises that do not load the joint under bodyweight. Acute swelling — sudden onset, warm to touch, significantly increased volume compared to baseline — is a signal to rest and consult your doctor before exercising. Exercising through an acute inflammatory flare can prolong it.

Can I do these exercises if I have had knee replacement surgery?

Knee replacement patients should follow their surgeon’s specific rehabilitation protocol, which will include supervised physical therapy. The exercises listed here may overlap with what a physical therapist prescribes post-replacement, but timing, load, and range of motion progression should follow clinical guidance specific to your surgery and implant. Do not substitute this guide for post-surgical PT.