Knee Lump or Mass

Overview

A knee lump or mass is any abnormal swelling, bump, or protrusion in or around the knee joint. These can occur on the front, sides, or back of the knee and may be caused by various conditions ranging from fluid-filled cysts to solid tumors. Most knee lumps are benign, but proper evaluation is important to determine the cause and appropriate treatment.

Common Causes

Cysts and Fluid Collections

  • Baker's cyst (popliteal cyst): Fluid-filled sac behind knee
  • Ganglion cyst: Jelly-filled sac near joint or tendon
  • Meniscal cyst: Associated with meniscus tears
  • Synovial cyst: From joint lining herniation

Bursitis

  • Prepatellar bursitis: "Housemaid's knee" in front of kneecap
  • Infrapatellar bursitis: Below the kneecap
  • Pes anserine bursitis: Inner side of knee
  • Semimembranosus bursitis: Back of knee

Bone and Joint Related

  • Osteochondroma: Benign bone tumor
  • Osteophytes: Bone spurs from arthritis
  • Exostosis: Bony outgrowth
  • Osgood-Schlatter disease: Bump below kneecap in adolescents
  • Patella alta/baja: Abnormal kneecap position

Soft Tissue Masses

  • Lipoma: Fatty tumor
  • Hemangioma: Blood vessel tumor
  • Fibroma: Fibrous tissue growth
  • Neuroma: Nerve tissue growth
  • Sarcoma: Rare malignant soft tissue tumor

Other Causes

  • Hematoma: Blood collection from injury
  • Abscess: Infected fluid collection
  • Rheumatoid nodules: In rheumatoid arthritis
  • Gout tophi: Uric acid crystal deposits
  • Aneurysm: Popliteal artery enlargement

Associated Symptoms

  • Pain or tenderness
  • Stiffness or limited range of motion
  • Swelling around the lump
  • Warmth or redness
  • Difficulty walking or bearing weight
  • Feeling of tightness behind knee
  • Clicking or popping sounds
  • Numbness or tingling (if pressing on nerves)
  • Changes in size with activity

Diagnostic Tests

  • Physical examination: Palpation and range of motion testing
  • X-ray: Shows bone abnormalities
  • Ultrasound: Identifies cysts and soft tissue masses
  • MRI: Detailed imaging of all structures
  • CT scan: For complex bone lesions
  • Aspiration: Fluid analysis from cysts
  • Biopsy: Tissue sample if tumor suspected
  • Blood tests: For infection or systemic conditions

Treatment Options

  • Observation: Monitor small, asymptomatic lumps
  • RICE therapy: Rest, ice, compression, elevation
  • Anti-inflammatory medications: NSAIDs for pain and swelling
  • Aspiration: Drain fluid from cysts or bursae
  • Corticosteroid injections: Reduce inflammation
  • Physical therapy: Strengthen surrounding muscles
  • Antibiotics: For infected lumps
  • Surgical removal: For persistent or concerning masses
  • Arthroscopy: Minimally invasive surgery

When to Seek Medical Attention

See a healthcare provider if:

  • Lump is rapidly growing
  • Severe pain or inability to bear weight
  • Signs of infection (fever, red streaks, warmth)
  • Lump is hard and fixed (doesn't move)
  • Associated with significant trauma
  • Numbness or weakness in leg
  • Lump persists more than 2 weeks
  • Multiple lumps appearing
  • Night pain or pain at rest
  • Unexplained weight loss

Prevention Tips

  • Proper warm-up before exercise
  • Use protective gear for contact sports
  • Maintain healthy weight
  • Strengthen muscles around knee
  • Avoid repetitive kneeling
  • Treat arthritis and joint problems
  • Proper technique in sports and activities