Knee Pain and Aetiology

Prof Nabil Ebraheim, University of Toledo, Ohio, USA

 

Knee pain is a very common complaint and may arise from:

• The knee cap (patella) itself

• The tendons attached to the patella (patellar tendon and quadriceps tendon)

• Structures inside or around the knee joint such as menisci, ligaments, bursae, or cartilage

 

1. Chondromalacia Patella (Patellofemoral Pain Syndrome)

• One of the most common causes of anterior knee pain

• Caused by softening and degeneration of the cartilage on the underside of the patella

• Cartilage may show:

  • Erosions

  • Defects

  • Partial or full-thickness damage

• Pain is felt in the front of the knee

• More common in young individuals

• Pain worsens with:

  • Climbing stairs

  • Going down stairs

  • Prolonged sitting

Treatment

• Non-steroidal anti-inflammatory drugs (NSAIDs)

• Physiotherapy

• Surgery is rarely required

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2. Prepatellar Bursitis

• Pain and swelling occur directly in front of the knee cap

• Caused by inflammation of the prepatellar bursa

• The bursa fills with fluid, leading to:

  • Swelling

  • Tenderness

  • Localized lump over the patella

• Pain in front of the knee above or below the patella may also suggest associated tendonitis

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3. Patellar Tendonitis (Jumper’s Knee)

• The patellar tendon works together with the quadriceps tendon to straighten the knee

• An overuse injury, commonly seen in athletes involved in jumping sports

• Accounts for approximately 20% of jumping-related knee injuries

• Pain is:

  • Activity-related

  • Located below the knee cap

• Tenderness is present at the distal pole of the patella

  • Tender in knee extension

  • Less tender in knee flexion

• Predisposing factors:

  • Quadriceps tightness or weakness

  • Hamstring tightness

  • Muscle imbalance or atrophy

Treatment

• Anti-inflammatory medications

• Stretching and strengthening exercises

• Hamstring and quadriceps stretching

• Eccentric strengthening programs

• Most early cases respond well to non-operative treatment

• Surgery (tendon debridement and repair):

  • Reserved for severe cases

  • Considered if symptoms persist after 6–12 months of conservative treatment

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4. Meniscal Tear

• The meniscus acts as a shock absorber, protecting knee cartilage

• Injury causes pain on the:

  • Medial (inner) or

  • Lateral (outer) joint line

• Common symptoms include:

  • Joint line pain

  • Swelling

  • Locking or catching sensation

  • Feeling of instability

• Joint line tenderness is the most important clinical finding

Clinical Test

• McMurray’s test

  • Painful click or pop during knee movement from flexion to extension with rotation

Imaging

• MRI is very helpful for diagnosis

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5. Knee Arthritis (Osteoarthritis)

• A very common condition, especially with increasing age

• Cartilage cells gradually degenerate and repair capacity decreases

• Leads to:

  • Progressive cartilage loss

  • Joint space narrowing

  • Bony changes visible on X-rays

• Symptoms include:

  • Pain

  • Stiffness

  • Reduced mobility

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6. Baker’s Cyst (Popliteal Cyst)

• A fluid-filled swelling located behind the knee

• Filled with synovial fluid

• Located between:

  • Semimembranosus tendon

  • Medial head of gastrocnemius

• Often associated with:

  • Arthritis

  • Meniscal tears

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7. Ligament Injuries of the Knee

• Commonly occur due to sports-related trauma

Medial Collateral Ligament (MCL) Injury

• Most commonly injured knee ligament

• Involves the ligament on the inner side of the knee

Anterior Cruciate Ligament (ACL) Injury

• Often caused by valgus stress and twisting injury

• Common features:

  • Sudden swelling

  • Hematoma

• Lachman’s test is usually positive

• MRI confirms the diagnosis

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8. Iliotibial Band Syndrome (ITBS)

• Caused by inflammation and thickening of the iliotibial band

• Results from repetitive friction over the lateral femoral condyle

• The IT band:

  • Extends from the iliac crest to the knee

  • Slides back and forth during knee movement

• Maximum impingement occurs around 30° of knee flexion

Clinical Features

• Pain on the outer side of the knee

• Swelling, tenderness, and crepitus over the lateral femoral condyle

• Common in:

  • Runners

  • Cyclists

  • Athletes with repetitive knee flexion-extension

• Pain may be reproduced with a single-leg squat

• Ober’s test assesses IT band tightness

Imaging

• MRI may show edema along the IT band

Treatment

• Primarily non-operative:

  • Rest and ice

  • Physiotherapy

  • Stretching exercises

  • Proprioceptive training

  • Training modification

• Local injection may help in selected cases

• Surgery is a last resort:

  • Excision of the inflamed or scarred segment of the IT band

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Summary

Knee pain can arise from multiple structures including the patella, tendons, menisci, ligaments, cartilage, and surrounding soft tissues.
A careful clinical examination, supported by appropriate imaging, is essential to identify the exact cause and guide treatment.