Knee Pain: Common Causes from Arthritis to Injuries

At-a-Glance

• Knee pain is extremely common, affecting people of all ages from athletes to seniors
• Most common causes include osteoarthritis, meniscus tears, ligament injuries, and overuse
• Location of pain (front, side, back, or inside knee) helps identify the cause
• Many cases improve with rest, ice, compression, and physical therapy
• Sudden severe pain, inability to bear weight, or significant swelling requires prompt evaluation

What It Feels Like

Knee pain can range from a dull ache to sharp, debilitating pain that limits mobility. The sensation varies depending on the underlying cause and can affect different parts of the knee.

Common descriptions include:

• Sharp, stabbing pain with movement
• Dull, aching pain that worsens with activity
• Stiffness, especially after sitting or upon waking
• Swelling or puffiness around the kneecap
• Popping, clicking, or grinding sensations
• Feeling of instability or the knee "giving out"
• Pain when climbing stairs, kneeling, or squatting
• Warmth or tenderness to touch

The pain may be constant or intermittent, and can occur during activity, at rest, or at night.

Common Causes

Osteoarthritis

Osteoarthritis is the most common form of knee arthritis, caused by wear and tear of the cartilage that cushions the knee joint. It typically affects people over 50 but can occur earlier.

Signs it might be osteoarthritis:

• Gradual onset of pain over months or years
• Morning stiffness lasting less than 30 minutes
• Pain worsens with activity, improves with rest
• Grinding or crunching sensation (crepitus)
• Reduced range of motion
• Swelling after activity
• Pain worse in cold or damp weather

Risk factors:

• Age over 50
• Previous knee injury
• Obesity (extra weight stresses joints)
• Repetitive stress on knee (certain occupations or sports)
• Family history

What helps:

• Weight loss (reduces joint stress)
• Low-impact exercise (swimming, cycling)
• Physical therapy to strengthen muscles
• NSAIDs for pain and inflammation
• Corticosteroid or hyaluronic acid injections
• Knee braces or supports
• Joint replacement in severe cases

Meniscus Tear

The meniscus is cartilage that cushions the knee joint. Tears can occur from sudden twisting motions or gradual degeneration with age.

Signs it might be a meniscus tear:

• Pain along the joint line (inside or outside of knee)
• Popping sensation at time of injury
• Swelling within 24 hours
• Difficulty straightening the knee fully
• Feeling of knee "locking" or catching
• Pain when twisting or rotating the knee
• Difficulty squatting

What helps:

• RICE protocol (Rest, Ice, Compression, Elevation)
• Physical therapy
• NSAIDs for pain
• Avoid activities that worsen pain
• Arthroscopic surgery for severe tears
• Many small tears heal with conservative treatment

Patellofemoral Pain Syndrome (Runner's Knee)

This common condition causes pain around or behind the kneecap, often affecting runners and people who do activities involving knee bending.

Signs it might be runner's knee:

• Pain in front of knee, around or behind kneecap
• Pain worsens with stairs, squatting, or prolonged sitting
• Grinding or popping sensation
• Pain after sitting with bent knees ("theater sign")
• More common in young, active people
• Gradual onset

What helps:

• Reduce or modify activities temporarily
• Strengthen quadriceps and hip muscles
• Improve running form and footwear
• Knee taping or bracing
• Stretching exercises
• Ice after activity
• Gradual return to activity

Ligament Injuries (ACL, MCL, PCL, LCL)

Ligaments stabilize the knee joint. Injuries range from mild sprains to complete tears, often occurring during sports.

ACL (Anterior Cruciate Ligament) Tear:

• Sudden "pop" during injury
• Rapid swelling
• Severe pain
• Instability, knee "giving out"
• Common in basketball, soccer, football

MCL (Medial Collateral Ligament) Sprain:

• Pain on inside of knee
• Swelling and tenderness
• Instability when walking
• Often from blow to outside of knee

What helps:

• RICE protocol immediately
• Knee brace or immobilizer
• Physical therapy
• Surgery for complete ACL tears (especially in athletes)
• Most MCL sprains heal without surgery

Bursitis

Bursae are fluid-filled sacs that cushion the knee. Inflammation (bursitis) causes pain and swelling, often from kneeling or direct trauma.

Signs it might be bursitis:

• Swelling in front of kneecap or below knee
• Warmth and tenderness
• Pain when kneeling or bending knee
• May develop gradually or after injury
• Common in people who kneel frequently (gardeners, carpet layers)

What helps:

• Avoid kneeling and activities that worsen pain
• Ice packs
• NSAIDs
• Knee pads for protection
• Aspiration (draining fluid) if severe
• Corticosteroid injection in some cases

Tendinitis (Patellar Tendinitis)

Inflammation of the patellar tendon, which connects the kneecap to the shinbone. Common in athletes who jump frequently.

Signs it might be tendinitis:

• Pain just below the kneecap
• Pain worsens with jumping, running, or stairs
• Tenderness when pressing on tendon
• Stiffness after rest
• Gradual onset
• Common in basketball and volleyball players ("jumper's knee")

What helps:

• Rest from aggravating activities
• Ice after activity
• Eccentric strengthening exercises
• Patellar tendon strap
• Physical therapy
• Gradual return to sports
• Platelet-rich plasma (PRP) injections for chronic cases

IT Band Syndrome

The iliotibial (IT) band is a thick band of tissue running along the outside of the thigh. Tightness causes friction and pain on the outer knee.

Signs it might be IT band syndrome:

• Pain on outside of knee
• Worsens with running, especially downhill
• Pain typically starts after a certain distance
• Tenderness on outer knee
• Common in runners and cyclists

What helps:

• Reduce mileage temporarily
• IT band stretching and foam rolling
• Strengthen hip abductors
• Correct running form
• Proper footwear
• Avoid running on cambered surfaces
• Physical therapy

Serious Causes Requiring Prompt Attention

Septic Arthritis (Infected Joint)

Bacterial infection in the knee joint is a medical emergency requiring immediate treatment.

Warning signs:

• Severe pain and swelling
• Fever and chills
• Warmth and redness
• Inability to move knee
• Feeling ill or unwell

Action: Seek emergency care immediately. Requires antibiotics and joint drainage.

Fracture

Broken bones around the knee can occur from falls, direct blows, or severe twisting injuries.

Warning signs:

• Severe pain immediately after injury
• Inability to bear weight
• Visible deformity
• Rapid, severe swelling
• Numbness or tingling below knee

Action: Seek emergency care. Requires X-rays and possible surgery.

Deep Vein Thrombosis (DVT)

Blood clot in leg veins can cause knee and calf pain.

Warning signs:

• Swelling in calf and/or knee
• Warmth and redness
• Pain in calf when flexing foot
• Recent surgery or prolonged immobility

Action: Seek immediate medical care. Can lead to life-threatening pulmonary embolism.

When to See a Doctor

Schedule a doctor's appointment if:

• Pain persists for more than a few days despite home treatment
• Swelling doesn't improve with rest and ice
• Knee feels unstable or gives out
• You can't fully straighten or bend the knee
• You have signs of infection (warmth, redness, fever)
• Pain interferes with daily activities or sleep
• You have a history of arthritis and symptoms worsen

Diagnosis

Your doctor may perform:

• Physical examination: Checking range of motion, stability, swelling
• X-rays: Detect fractures, arthritis, bone abnormalities
• MRI: Visualize soft tissues (meniscus, ligaments, tendons)
• CT scan: Detailed bone imaging
• Ultrasound: Check for fluid, Baker's cyst, tendon issues
• Joint aspiration: Remove and analyze fluid if infection or gout suspected
• Blood tests: Check for rheumatoid arthritis or infection

Treatment and Management

Immediate Care (RICE Protocol)

• Rest: Avoid activities that cause pain
• Ice: 15-20 minutes every 2-3 hours for first 48-72 hours
• Compression: Elastic bandage to reduce swelling
• Elevation: Keep knee elevated above heart level

Medications

• NSAIDs: Ibuprofen, naproxen for pain and inflammation
• Acetaminophen: Pain relief without anti-inflammatory effect
• Topical creams: Diclofenac gel, capsaicin cream
• Corticosteroid injections: For severe inflammation
• Hyaluronic acid injections: For osteoarthritis

Physical Therapy

• Strengthening exercises (quadriceps, hamstrings, hip muscles)
• Stretching and flexibility exercises
• Balance and proprioception training
• Gait training
• Manual therapy techniques

Supportive Devices

• Knee braces or sleeves
• Patellar straps for tendinitis
• Orthotics or shoe inserts
• Walking aids (cane, crutches) if needed

Surgical Options

• Arthroscopy: Minimally invasive repair of meniscus or cartilage
• ACL reconstruction: For complete ligament tears
• Partial knee replacement: Replace damaged portion
• Total knee replacement: For severe arthritis
• Cartilage restoration procedures: For younger patients

Self-Care and Prevention

Exercise and Strengthening

Quadriceps strengthening:

• Straight leg raises
• Wall sits
• Step-ups

Hamstring strengthening:

• Hamstring curls
• Bridges

Hip strengthening:

• Clamshells
• Side leg raises
• Hip abduction exercises

Low-impact cardio:

• Swimming
• Cycling
• Elliptical machine
• Water aerobics

Lifestyle Modifications

• Maintain healthy weight: Every pound lost reduces 4 pounds of pressure on knees
• Wear proper footwear: Supportive shoes with good cushioning
• Warm up before exercise: Prepare muscles and joints
• Avoid high-impact activities: If you have arthritis or chronic pain
• Use proper form: When exercising or lifting
• Gradually increase activity: Avoid sudden increases in intensity or duration

Daily Habits

• Take stairs one at a time if painful
• Use handrails for support
• Avoid prolonged kneeling or squatting
• Change positions frequently
• Apply ice after activities that stress the knee
• Consider knee-friendly exercises (swimming, cycling)

Frequently Asked Questions

The Bottom Line

Knee pain is extremely common and can result from many causes, ranging from overuse and arthritis to acute injuries like meniscus tears or ligament sprains. The location, onset, and characteristics of pain provide important clues to the underlying cause.

Most knee pain responds well to conservative treatment: rest, ice, compression, elevation, physical therapy, and appropriate exercises to strengthen supporting muscles. Maintaining a healthy weight is one of the most effective ways to reduce knee stress and prevent pain.

However, certain warning signs—severe pain after injury, inability to bear weight, significant swelling, fever, or knee instability—require prompt medical evaluation. Early diagnosis and treatment can prevent complications and improve outcomes.

If you're experiencing persistent knee pain that interferes with daily activities, don't dismiss it as a normal part of aging or "just arthritis." Many effective treatments are available, from physical therapy and injections to surgical options for severe cases.

Remember: This information is educational and doesn't replace professional medical advice. If you're experiencing persistent or severe knee pain, consult a healthcare provider for proper evaluation and treatment.