Knee pain affects about a fifth of over-16s, and is more common the older we get.

Per the NHS, it can be caused by everything from strains and twists during exercise to conditions like osteoarthritis (knee osteoarthritis seems to be the most common form of the disease).

According to Dr Syed Nadeem Abbas, a surgeon and regenerative medicine expert from the Knee Pain Clinic, “most knee pain [among over-40s] comes down to wear and tear, and that’s still the most likely explanation.”

However, he says one type of knee pain should always be investigated.

“What tends to get missed is pain that doesn’t follow the usual rules, pain that’s worse at rest than at activity, or wakes someone up at night rather than settling,” the expert said.

“That’s the pattern I’d always want checked properly rather than put down to getting older, because catching anything unusual early makes a real difference to the outcome.”

Knee pain caused by osteoarthritis or overuse tends to ease off at rest, he added.

But issues that get worse at night might very rarely be caused by a bone tumour, he added – indeed the NHS said a possible symptom of bone cancer is if “pain or tenderness in a bone, particularly if it’s worse at night”.

Chondrosarcoma, the most common type of primary bone cancer, is known to affect adults over 40, the surgeon added.

Of course, these symptoms aren’t limited to your knee: common sites include the pelvis (hip), rib cage, arms, shoulder blades, and other parts of your leg.

It’s important to remember that primary bone cancer is very uncommon – about 550 people in the UK face it yearly.

Other conditions which can cause nighttime knee pain include:

• Rheumatoid arthritis,
• Gout,
• Tendonitis,
• Prepatellar bursitis,
• Osgood-Schlatter disease,
• Injury, per The Cleveland Clinic.

Dr Abbas added that even vitamin D deficiency might cause unexpected knee pain.

But as orthopaedic surgeon Dr Kim Stearns also told the clinic, “People with healthy knees usually don’t get pain at night. There’s typically a reason, and it can be caused by several conditions.”

Speak to your GP if you have concerns.