4.11 Arthritis

Deterioration of the joints over time
Osteoarthritis occurs when some combination of mechanical wear and biochemical degradation erodes the articular cartilage
It is a localized effect most common in knees and hips
Damage to articular cartilage may be caused by normal wear, disease, or trauma
Damage may be direct or due to changes in the subchondral bone
May also be caused by altered joint mechanics
- ie change in gait due to ankle fusion leads to arthritis in the knee
Damage may be caused by systemic disease
- Rheumatoid arthritis

Traumatic loads may cause ruptures of ligaments, tendons, and the menisci
Damage may occur in the ligament/tendon itself or in the attachment point to the bone or muscle
- May be entirely within the bone
The nature of the injury can depend on the rate of loading
- Tendons/ligaments exhibit viscoelastic behavior

Musculoskeletal system has an extraordinary ability to repair itself (if the damage is not too severe)
Bone is continually “damaged” and continually repairs itself
- Damage may be related to the adaption process and necessary to maintain bone density
Self repair varies with site, tissue, and extent of the injury
- Bone is good at self repair
- Muscle, tendon, and ligament are not as good at self repair
Severe damage may necessitate medical or surgical intervention