How to address common causes of knee pain

It might be osteoarthritis, wear and tear of the joints, the most common cause of knee pain in people over 60, according to Sydney-based Orthopaedic Surgeon Dr George Gayagay - although he is now seeing younger patients with osteoarthritic knee pain due to obesity.

For people in their 30s and 40s, inflammatory (autoimmune or metabolic) and post-traumatic osteoarthritis are the most likely causes of knee pain, Gayagay said. For the teens to early 30s age bracket, a ligament, sporting or trauma injury is typically to blame.

“Sharp, burning or dull,” the pain can be localised to one aspect of the knee or throughout, potentially referring to the back or the hip, Gayagay said. “It is made worse by activity and relieved with rest,” and the knee might click, lock or give way. Some cannot walk, sleep, or rest comfortably.

“Knee pains arising from injury and arthritis are similar in profile.”

However while knee pain from injury is acute (sudden), often settling after sufficient convalescence, “knee pain from arthritis is often insidious and progressive…eventually [requiring] surgical intervention.”

Cartilage is affected by any form of arthritis. It does not heal or regenerate, unlike the ligaments and bones affected by injury, Gayagay said.

Risk factors for knee pain

“As we age, tissues deteriorate and metabolism slows,” resulting in numerous contributors to knee pain: muscle weakness, cartilage degradation, osteoporosis (‘soft bones’) and obesity.

“Your knee experiences five to seven times of your body weight,” Gayagay said.

Diagnosis

A thorough medical history and physical examination determine the cause of the pain, complemented by “at least three weight-bearing x-ray views of the knee. [If the x-ray is normal, an MRI may] identify soft tissue problems,” Gayagay said.

Blood tests rule out infection, gout (an arthritis involving uric acid crystals depositing in the joints), and inflammatory arthritis.

Treatment

Initially, analgaesics such as paracetamol provide pain relief, and walking aids help offload the knee. Physiotherapy reduces swelling, facilitates mobility and strengthens the knee muscles and the core of the body; “knee pain can cause muscle weakness via a negative feedback mechanism,” Gayagay said.

Injections into the knee such as hyaluronic acid may be administered. Steroids are not a long-term treatment option “because of their potentially destructive side effects.”

Gradual weight loss needs emphasising in the obese patient with the assistance of a dietitian and potentially a bariatric (obesity) surgeon, Gayagay said.

“[If] all [non-surgical] options have been exhausted and knee pain remains, then surgical interventions can take [place].”

For post-traumatic osteoarthritis, a knee arthroscopy (a day procedure) removes damaged tissue, although this is becoming decreasingly common.

In chronic osteoarthritis, an osteotomy – breaking of the bone and realigning of the joint is “ideal…for the young labourer patient with arthritis at only one area of the knee.”

‘Limited arthroplasty’ is “also ideal for the younger patient,” replacing only the arthritic component of the knee. “Recovery is quicker, but longevity is shorter compared to a total knee replacement, a [well-studied, engineered and] reliable surgical option for [generally arthritic] knees.”

Pain after a knee replacement can be managed with analgaesics, walking aids and physiotherapy. Driving with the operated knee can generally commence at week six. Return to manual-type work is realistic eight to 12 weeks post-surgery, and clerical-type work can start at four to six weeks, Gayagay said.

“Almost all patients by one year are happy with their outcome…a replaced knee is a stable knee.”

When to see your doctor

If an infection, fracture or dislocation is suspected, “go to the emergency department immediately,” Gayagay said.

For a gradually aching knee, “see your GP [when convenient] for a diagnosis and appropriate investigations. A minimum of a [knee x-ray] should be undertaken.”