Knee Pain

Chronic knee pain troubles a significant number of people worldwide. It is a common problem amongst the aging population, and can indeed be very painful and debilitating, sometime even confining individuals to the bed. The most common cause of knee pain in elderly is osteoarthritis (OA), a condition where the cartilages of the knee joint have worn out due to wear and tear. This results in friction between the bones of the joint during movement which results in pain. The impact is more in overweight and obese because of the extra load on the knees. The risk of knee OA in overweight women is nearly 4 times and in overweight men is 5 times greater. It is not just the mechanical factors which promote OA in obesity but also the co-existence of disordered glucose and lipid metabolism and the highly metabolic and inflammatory environments have a significant role.

Causes

The causes of knee pain following replacement surgery can be located inside the joint (intra articular causes) or outside the joint (extra articular causes).

The intra articular causes include:

Knee joint instability
Loosening of the implant
Infection of the bone or the joint space
Problems related to the kneecap (patella)
Osteolysis (loss of bone)
Issues related to size or type of implant

It is important to rule out the extra articular causes when a patient complains of persistent knee joint pain following surgery, because they can have serious consequences if they are missed.

The extra articular causes include:

Localized knee problems such as tendinitis and bursitis
Pain radiating from the nearby joints/body parts such as spine, hip and ankles
People who have ongoing psychological illnesses will also tend to experience longer postoperative pain
Nerve injuries/ problems

Investigation

Your doctor will go through multiple steps in order to evaluate the pain you are experiencing. This process includes, taking a detailed history of the pain, such as when what type of pain you are experiencing and when you experience it the most. Then your doctor will go on to examine the knee, which will help him/her to further narrow down on probable causes & identify problems such as stiffness, swelling, and issues with alignment of the joint. You will be asked to undergo investigations such as, X-ray, MRI, blood tests including inflammatory markers such as CRP and ESR etc.

Treatment

Depending on the cause of your pain, you doctor may suggest a variety of treatment plans. On some occasions pain relief medication may help to control the pain, and even get rid of it completely. Physiotherapy is another option which has proven to be effective in managing pain following knee replacement surgery. Nerve blocks are sometimes offered if nerves are suspected to be the pain generator. Initial management involves lifestyle modification, supplements, simple pain killers and physiotherapy. It is estimated that an extra Kg of weight exerts a force of nearly three to six times across the knee while walking. Thus, weight loss is an important modifiable factor in the treatment of knee OA which the affected individual can drive. Various studies have demonstrated that weight loss improves both pain and function in obese subjects with knee OA. Local injections are considered depending on the severity of problem and other factors such as age, functional status etc. When the pain and discomfort is severe your doctor may offer you the option of undergoing a knee replacement surgery. This involves removal of the worn out part of joint, shaping the ends of the bone and placing a metal implant. This reconstruction of the knee joint allows for smooth, pain free movement for most individuals. However some, even following the rehabilitation process, continue to experience pain.

For those who are
Not keen on the replacement surgery or
Not fit to have one or
Continue to have pain after knee replacement surgery

Cooled Radiofrequency or Radiofrequency ablation of genicular nerves is an alternative treatment. This procedure is based on a theory that blocking the nerve supply to a painful area may alleviate pain and restore function. The knee joint is innervated by the articular branches of various nerves, including the femoral, common peroneal, saphenous, tibial, and obturator nerves. These branches around the knee joint are known as genicular nerves. Several genicular nerves can be easily approached with a needle under fluoroscopic guidance. Patients can get a diagnostic genicular nerve block to determine if this will provide adequate relief. Patients with a positive response are offered radiofrequency ablation for a more sustained response. The procedure is usually done under fluoroscopic guidance to ensure accuracy of needle placement. Patients need to be aware that the outcome of the procedure is variable and they may not receive the desired benefits. This involves creating a heat lesion around the genicular nerves carrying painful impulses from the knee joint. Successful treatment can result in pain relief lasting several months. Treatment is performed under local anaesthetic and can take 4 to 6 weeks to work.