Clinical features
OA can occur in any joint but most often it affects the fingers, toes, knees, hips, and spine; usually OA develops slowly.
Symptoms
By the age of 40 many people show some evidence of OA on X-ray or other imaging such as Magnetic Resonance Imaging (MRI) scan but may have no symptoms.
Relatively few people with OA have significant symptoms, which usually develop gradually affecting one or a few joints at first, although some people develop OA suddenly.
Pain and stiffness typically made worse on initiation of movement, is usually the first symptom. Stiffness of the joint after sleeping or prolonged inactivity is also common. This usually wears off within minutes of active use of the joint. However, continuing movement of the joint leads to worsening (crescendo) pain.
Signs
The main signs of OA are joint deformity, restriction of joint movement and swelling (effusion). As the joint changes of OA worsen, the range of movements of the joint becomes less, with consequent loss of function. This may result in disuse of the joint or joints, with consequent muscle wasting and further functional limitations.
The growth of new bone and other tissue can cause joints to enlarge and become misshapen. The roughened cartilage causes joints to crackle or grate on movement.
The presence of osteo-arthritis on X-ray or other imaging does NOT equate with functional restrictions or symptoms. Many people with significant X-ray or imaging changes have no pain or functional limitations.
X-ray changes are only significant where they support the clinical picture.
The Knees
The knee joints are frequently affected by OA. They may become stiff, swollen and painful with reduction in movement.
Movements:
- At least 45 degrees of flexion (bending) in one knee is required for walking or climbing stairs
- At least 90 degrees of flexion in one knee is required to rise from a chair or to put a foot on a chair to tie a shoelace
- Squatting requires the maximum 135 degrees of flexion in both knees
- Full knee extension (straightening) is required to walk safely and steadily, but full flexion (bending) is not necessary.
Laxity or injury to ligaments and cartilage (menisci) in the knee may occur. This may indicate significant disability in the form of giving way of the joint.
Signs of damage to the menisci may indicate reduced function if full extension (straightening) is obstructed and this leads to locking and instability as the person may be aware of a sensation of the joint giving way. If there is no instability, locking does not give rise to a significant functional deficit. If surgery has previously been undertaken on the cartilage of the knee joint, then OA will almost invariably develop in the future.
The Hips
Hip joints affected by OA have a limited range of movement.
- Climbing stairs requires at least 35 degrees of hip flexion (bending) with normal knee and ankle function on that side.
- Walking requires at least 30 degrees of hip flexion.
- Sitting in an upright chair requires at least 90 degrees of hip flexion.
- Rising unaided or using a single cane requires at least 110 degrees of hip flexion.
- Reaching low, for example, down on one knee, requires at least 90 degrees of hip flexion.
- To reach the floor can be achieved with 90 degrees of hip flexion and 90 degrees of knee flexion on both sides.
- To reach an oven safely can be achieved with a combination of 30 degrees of hip flexion and 60 degrees of knee flexion on both sides.
- Decreased hip movement has been shown to correlate with decreased walking speed and step rates as well as reduction in ability to stand with weight on one leg.
- Limitation of movement and under use predisposes to muscle weakness and wasting.
The Low Back
There may be few signs even with fairly advanced disease. The main signs are lack of back movements and if there is nerve compression in the spine due to osteophytes or associated disc degeneration, there may be neurological signs in the legs.
The Hands
OA of the fingers is often hereditary. OA of the fingers (nodal) tends to occur more commonly in women. A characteristic development is small bony knobs called Heberden’s nodes, which appear on the end joints of the fingers. Similar knobs called Bouchard’s nodes can appear on the middle joints of the fingers. The base of the thumb joint is also commonly affected by OA, often resulting in considerable pain of the joint.
The Elbows
The elbow joint is infrequently affected by Osteo-arthritis. When OA develops in the elbow joint, there is usually a history of injury to the joint. As the disease progresses, a fixed flexion deformity may develop so that the elbow cannot be straightened fully. Rotational movements at the elbow (supination/pronation) are also likely to be reduced. Arthritis of the elbow joint can be treated by replacing the entire joint with a prosthesis.
The Shoulders
The shoulder joint is affected infrequently by Osteo-arthritis. Although most people think of the shoulder as a single joint, there are really two joints in the area of the shoulder. One is located where the collarbone (clavicle) meets the tip of the shoulder bone (acromion). This is called the acromioclavicular or AC joint. The junction of the upper arm bone (humerus) with the shoulder blade (scapula) is called the glenohumeral joint. Both joints may be affected by arthritis.
Limited joint movement is likely. In severe glenohumeral arthritis it is unlikely that the arm can be lifted up by more than 20 degrees. A grating sound (crepitus) may be heard as the shoulder is moved.
The Neck
The cervical spine is a complicated structure and consists of bony vertebrae, the inter-vertebral discs, spinal joints, ligaments, the spinal canal and nerve roots. Pain may arise from any of these structures, but as with back pain most episodes of neck pain are not associated with any identifiable structural abnormality.
Cervical Spondylosis is the commonest cause of neck pain. This is a term commonly used for longstanding non-specific neck pain, often caused by age related degeneration (‘wear and tear’) of both the vertebrae and inter-vertebral discs in the neck.
In the majority of cases it is unlikely that any significant functional restrictions will be present. Rarely, significant functional restrictions can occur due to outgrowths of bone from the vertebrae due to the OA process, and pressure from bulging discs. Compression of the spinal cord may then occur. This condition is called cervicalmyelopathy.
