Knee joint / Knee pain:

The knee is a joint that has three compartments. The thigh bone (femur) meets the large shin bone (tibia) forming the main knee joint. This joint has an inner (medial) and an outer (lateral) compartment. The kneecap (patella) joins the femur to form a third compartment, called the patellofemoral joint.

The knee joint is surrounded by a joint capsule with ligaments strapping the inside and outside of the joint (collateral ligaments) as well as crossing within the joint (cruciate ligaments). These ligaments provide stability and strength to the knee joint.

The meniscus is a thickened cartilage pad between the two joints formed by the femur and tibia. The meniscus acts as a smooth surface for motion and absorbs the load of the body above the knee when standing.

The knee joint is surrounded by fluid-filled sacs called bursae, which serve as gliding surfaces that reduce friction of the tendons. Below the kneecap, there is a large tendon (patellar tendon) which attaches to the front of the tibia bone. There are large blood vessels passing through the area behind the knee (referred to as the popliteal space).

The large muscles of the thigh move the knee. In the front of the thigh, the quadriceps muscles extend the knee joint. In the back of the thigh, the hamstring muscles flex the knee. The knee also rotates slightly under guidance of specific muscles of the thigh.

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The knee functions to allow movement of the leg and is critical to normal walking. The knee flexes normally to a maximum of 135 degrees and extends to 0 degrees. The bursae, or fluid-filled sacs, serve as gliding surfaces for the tendons to reduce the force of friction as these tendons move. The knee is a weight-bearing joint. Each meniscus serves to evenly load the surface during weight-bearing and also aids in disbursing joint fluid for joint lubrication.

Knee pain:

Osteoarthritis is commonest cause of knee pain and discussed here

Osteoarthritis is one of the commonest joint problems with 80% of general population of radiologic evidence of osteoarthritis by 65 yrs of age. The disease process starts by age of around 20 yrs and manifest around 40 yrs. More than 40% of sufferers have no radiological evidence of osteoarthritis.

Pathogenesis

Exact etiology is not known. By chemical stress on articular cartilage and subchondral bone leads to wear and tear to these structures.

Joint inflammation is very minimum compare to other arthritis and seen mostly in advanced disease. Pain of osteoarthritis may be due to following reasons:

  1. Trabecular micro-fracture
  2. Intraosseous hypertension
  3. Periosteal irritation
  4. Synovitis
  5. Stretching of join capsule and ligaments
  6. Muscle spasm

Central sensitization contributes considerably in producing pain.

Clinical features

Pain around the joint that increases with weight bearing and movement and improves with rest is the commonest presenting symptom.

It may be associated with morning stiffness and swelling of the joints. Clinical signs are tenderness, crepitus, joint effusion, decreased range of movement, deformity of joint etc.

X-ray shows decreased joint space, osteophytes(extra bone) formation and osteoporosis of subchondral bone.

Treatment

  1. Non-pharmacological therapy
    1. Reduction of obesity- loss of weight decreases load on the weight bearing joints and thereby retards the disease process.
    2. Quadriceps strengthening exercises- It is very useful for patients with osteoarthritis of knee. Strengthening of quadriceps muscle improves knee pain and function.
    3. Walking stick to be held in the opposite hand of the affected joint reduces the load on the joint and is associated with decreased pain and improved function.
    4. Deformity stabilization- use of proper shoes transfers the load to the other compartment and retards the disease process.
  2. Pharmacological therapy
    1. Different types of pain killers
    2. There are some diseases modifying agents that have generated a lot of
      interest. Some of them help in regeneration of cartilage and others inhibit
      degeneration. The agents which help in regeneration are chondroitin
      sulphate and gulcosamine sulphate.
  3. Interventions: joint injection
    1. Intraarticular injections-patients with severe pain of knee, joint effusions and local signs of inflammation benefit by intraarticular injections of steroids (triamcinolone 40 mg). This will be effective for short term period in reducing pain and increasing quadriceps strength. Some patients will require about 3 to 4 injections in a year, to using aseptic precautions, the infection rate is negligible. Sometimes mild flare up might be seen in joint inflammation following intraarticular injections, more than 3 to 4 injections in a year, should be considered for either joint lavage or surgery. Repeated injections (>4/year) are not recommended for the fear of damaging the cartilage of weight bearing joints.
    2. Tidal irrigation- The principle is washing off the inflammatory mediators, debris and breaking adhesions. Closed tidal knee irrigation with normal saline is done under local anaesthesia; this is as good as arthroscopic lavage. Saline is infused into the knee to distend the capsule and then is withdrawn. A total of 1 ½ to 2 litres is used for this kind of irrigation. Patients feel improvement in their joint mobility along with reduction of stiffness. This procedure has to be done under aseptic precautions.
    3. Arthroscopy- This will be useful in meniscal tear and other internal derangements.
    4. Surgery- patients having very severe symptoms should be considered for surgical options like tibial osteotomy, arthroplasty and joint replacement. Surgical options should be considered, once medical line of treatment fails. Surgical options should be delayed as much because the total joint arthroplasty might last between 10-20 years. Patients will have to modify his/her lifestyle to certain extent because of the ergonomics of replaced joint.
    5. Prolotherapy and Prolozone Therapy. Injection of tissue proliferants (like ozone, dextose etc.) inside the joint and around the joint reduces pain, inflammation and it strengthen ligaments. It is also claimed that it promote cartilage growth.
    6. Stem cell therapy- Like its usefulness in other degenarative diseases, it is useful in osteoarthritis of knee also.
    7. Pulsed Radio- Frquency Procedure (PRF)- This procedure is under evaluation. PRF is also effective in nociceptive pain by reducing inflammation.