Osteoarthritis

Osteoarthritis is extremely common, and affects a majority of people over the age of 60, in one way or another.

Osteoarthritis is most frequently just referred to as ‘arthritis’, although ‘osteoarthritis’ is the more correct term --- to differentiate it from the other main kind of arthritis, which is Rheumatoid Arthritis (which is very different).

Osteoarthritis is where the articular cartilage in the joint (the smooth, white, shiny layer of tissue that covers the ends of the bone surfaces in the joint, to make them low friction) wears away. If the articular cartilage wears away completely then this exposes areas of bare bone, and when there is bare bone rubbing on bare bone in the knee, then this is arthritis.

Osteoarthritis can be either ‘primary’ or ‘secondary’:-

  • Primary Osteoarthrits is where a joint becomes diseased and damaged without any particular specific underlying cause (such as damage from trauma). It is often referred to as ‘wear and tear’ or ‘degeneration’ of the joint. There is a genetic element to Primary Osteoarthritis, i.e. it often runs in the family.
  • Secondary Osteoarthritis is where a joint becomes arthritic specifically because of some particular previous issue. Most commonly, this is due to previous trauma (such as meniscal tears, ligament ruptures or fractures). Anything that affects the joint congruity, alignment or contact pressures within the knee will increase the rate of wear and tear and therefore increase the likelihood of the joint becoming arthritic.

Symptoms

The typical symptoms of an arthritic knee are:-

  • Pain. The pain tends to be a constant deep achy pain deep inside the joint (or over to one side (medially or laterally) or at the front (anterior) if just one part of the joint is affected). The pain often radiates down the shin. The pain is often worse in cold or damp weather and it is aggravated by doing too much exercise, e.g. long walks. The knee also tends to feel worse towards the end of the day, and if the arthritis is bad then there may be night pain that can affect people’s sleep. At the same time, people also often complain of intermittent sudden sharp pains in the knee – these can be due to rough, torn, unstable or loose bits of cartilage catching in the joint. Degenerate meniscal tears are extremely common in arthritic knees (and often, addressing the meniscal tear can make the arthritic knee feel a whole lot better, and can delay the time when anything bigger, such as a knee replacement, might need to be done).
  • Swelling. The swelling in arthritis of the knee tends to be a global diffuse swelling around the knee. This is partly due to an increased build up of joint fluid in the knee (an effusion) and also often partly due to the formation of osteophytes (bony spurs) that develop around the edges of the joint.
  • Stiffness. Arthritis joints often feel stiff, and have a reduced range of motion. The is partly because of the damaged joint surfaces, partly because of the osteophytes, but also partly because the soft tissues around the knee also become thickened and tight, such as the capsule, the ligaments and the tendons.
  • Deformity. As the joint surfaces begin to wear down, the knee can end up becoming deformed. If the wear and tear is mainly on the medial (inner) side of the knee then the knee will begin to drift into varus (i.e. become bow-legged). If the damage is mainly on the lateral (outer) side, then the knee will gradually bend into valgus (knock-kneed). Also, with more severe arthritis is it not uncommon for there to be a ‘fixed flexion deformity’, which means that the knee won’t straighten out fully.
  • Giving Way or Locking. If the knee gives way or locks up (gets stuck suddenly in one position), then this implies that there are torn or loose bits of meniscal cartilage or articular cartilage (or sometimes bony loose bodies) inside the knee. People with these types of ‘mechanical symptoms’ are often good candidates for knee arthroscopy (keyhole surgery) to fix the cause, which can make the knee feel a lot better, even though keyhole surgery doesn’t ‘cure’ the underlying arthritis.

Investigation

The best investigation for arthritis is an X-ray. There are different X-ray views that are specifically useful for checking for different specific things:-

  • to check for arthritis in the tibiofemoral compartments (medial and/or lateral) one should get a weight-bearing anteroposterior (AP) view
  • to be thorough, one should also get a Rosenberg view (weight-bearing, but with the knee bent to about 30 degrees)
  • one should always also get a lateral view of the knee (looking from the side)
  • if you want to see the shape of the patellofemoral joint and/or check the position of the patella (patellar tracking), then you also need a patellar skyline view (also sometimes called a ‘sunrise view’ or a ‘Merchant view’)

If there is any suspicion of potential meniscal cartilage tears in the knee or possible loose bodies, then as well as a full set of X-rays you will also need an MRI scan.

Treatment

The most appropriate way to approach the treatment of osteoarthritis of the knee is to start with the small, easy and safe options, and then to work one’s way up what is sometimes referred to as ‘The Therapeutic Ladder’, as necessary. So, in order of ease and preference, the available treatments are:-

  • activity modification (simply avoiding whatever hurts!)
  • simple painkillers / anti-inflammatories

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