Osteoarthritis of the Knee (OA)

Osteoarthritis (also called OA or degenerative joint disease) is the deterioration of the cartilage of the knee leading to the narrowing of the joint space.  Cartilage acts as a cushion in joints.  The possible result of deterioration of the cartilage is direct bone on bone contact.

Work-Related Risk Factors

·Awkward knee postures

·Repetitive knee flexion (e.g. bending, kneeling, squatting, and climbing)

·Walking more than two miles a day on a regular basis

·Lifting 55 pounds or more on a regular basis

Osteoarthritis can also be caused by injuries to the knee joint and obesity.  There may be a genetic tendency to develop OA.

Development and Progression

Frequently bending the knee while performing activities such as kneeling, squatting, climbing, and heavy manual material handling may create pressure on structures in the knee (compressive forces).  These compressive forces gradually wear down the cartilage, leaving no cushioning between the bones.  With the loss of this protective cushioning, the synovial lining and bones thicken, which in turn causes a build up of fluid known as "water on the knee.  "Bone spurs can develop in many cases.

Common Symptoms

Individuals with OA often complain of stiffness and pain in the affected joint.Swelling and redness of the affected joint is common.  Up until the latter stages of OA, pain is often relieved with rest.

Common Treatment

Exercise, weight loss, and bracing of the knee can be effective therapies for resolving pain due to OA.  Nonsteroidal anti-inflammatory drugs (NSAIDs, e.g. ibuprofen or naproxen) and other medications are often helpful.  Other treatments include rest, heat applications, and physical therapy.  Injections of corticosteroids ("cortisone injections") may be beneficial in the short term.

Surgical treatment, including arthroscopy, osteotomy, and arthroplasty (joint replacement), are sometimes necessary to regain normal function in the knee joint.

Alternative treatments such as acupuncture, magnetic pulse therapy, vitamin regimes, and topical pain relievers have also been shown effective for some in the resolution of symptoms of OA.

Frequent squatting may cause musculoskeletal disorders of the knee, including osteoarthritis (degenerative joint disease).  Biomechanical studies have shown that forces in the knee are highly increased when the knee is deeply bent beyond 120 degrees.  Forces during deep squatting are approximately three to five times the body weight.  These forces can lead to cartilage loss and eventually to osteoarthritis.

Several epidemiologic studies have examined the link between squatting/kneeling and musculoskeletal disorders of the knee.  In a national survey of working adults (aged 33-41) the incidence of musculoskeletal disorders including knee injuries was found to be linked to the hazardous job activity of kneeling or crouching.  Workers who kneel or squat frequently often experience higher rates of knee disorders.  Other studies have shown that squatting increases the risk of moderate to severe knee osteoarthritis and knee pain while kneeling does not.

In construction workers, the greater amount of time spent in a kneeling posture has been linked with increased prevalence of low back pain and severe low back pain.