What Your Knee Says About Your Health

Spoiler: it says more than you might think!

Dr. Siobhan Deshauer explains:

Don’t neglect these signs

Here’s what to watch out for:

• Knee hyperextension (sign of hypermobility or Ehlers-Danlos syndrome): if your knees bend the wrong way more than 10°, this indicates ligament laxity and can be part of generalized joint hypermobility. The Beighton score tests flexibility in your fingers, thumbs, elbows, and spine. High scores suggest Ehlers-Danlos syndrome, especially if your skin is stretchy or bruises easily.
• Bow legs (sign of osteoarthritis or Paget’s disease): a gap wider than three fingers between your knees when your ankles touch suggests bow-leggedness. In adults, this often results from osteoarthritis, where cartilage loss alters the joint angle. Osteoarthritis is linked to inflammation, diabetes, high cholesterol, kidney and heart disease, and even mental health problems. If the bones themselves thicken and deform, Paget’s disease might be responsible due to disordered bone remodeling.
• Finger clubbing (possible hidden cancer, hypertrophic osteoarthropathy): swollen knees with nail clubbing and bone inflammation can indicate hypertrophic osteoarthropathy, which is often caused by lung cancer or another internal malignancy.
• Inflammatory arthritis (autoimmune conditions): stiffness and pain that improve with movement suggest autoimmune inflammation. Patterns help identify the cause:
  • with bowel symptoms: inflammatory bowel disease such as Crohn’s disease or ulcerative colitis
  • with itchy ears or scaly skin: psoriasis leading to psoriatic arthritis
  • with swollen knuckles: rheumatoid arthritis
  • with a butterfly rash: lupus
  • with daily fevers and rashes: adult-onset Still’s disease
  • with tight skin and pale, cold fingers: scleroderma
• Lyme arthritis (infection after tick bite): a tick bite from Borrelia burgdorferi can cause large, single-knee swelling months later. The disease will often also inflame nerves, the brain, or the heart. If a tick has been attached for at least 24 hours, a single antibiotic dose can prevent infection, but talk to your doctor, because antibiotics are not to be taken frivolously (they can wipe out your gut bacteria, cause an overgrowth of gut fungus, and ultimately kill you; it’s obviously not the usual outcome of taking a single antibiotic dose, but it is a very good reason to to not rush to take antibiotics “just in case”).
• Xanthomas (indicator of metabolic disease): yellowish fatty bumps around your knees, Achilles tendons, or buttocks can reveal high cholesterol, diabetes, or fatty liver disease.
• Gout (uric acid buildup) hard lumps around your knees, toes, or fingers show uric acid crystal deposits. This can result from kidney disease or genetics, and raises the risk of kidney and heart problems.
• Septic arthritis (medical emergency): a red, hot, swollen knee with fever or inability to walk may indicate a joint infection. It can destroy cartilage within hours and may be life-threatening if untreated, so: get thee to a hospital, and speedily.
• Hemarthrosis (bleeding into the joint): blood in your knee without injury can result from excessive blood thinners, hemophilia, vitamin C deficiency, or cancer invading the bone. It needs urgent drainage to prevent joint damage, and also obviously to check it’s not a symptom of something else that also needs treating (e.g. cancer)
• Symptoms not otherwise mentioned (sudden swelling, intense pain, fever, nighttime pain, or inability to bear weight): these require emergency care to prevent permanent damage or serious complications, beyond the scope of what a 16-minute article (or our write-up here) can provide.

For more on each of these plus visual illustrations, enjoy:

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Take care!