Osteoarthritis
It is a chronic disorder in which there is progressive softening and disintegration of the articular cartilage associated with new growth of the cartilage and bone at the joint margin (osteophyte) with fibrosis of the capsule.
Types:
? Primary Osteoarthritis, in which no obvious cause.
? Secondary osteoarthritis, follow a demonstrable abnormality.
Causes; osteoarthritis results from disparity between stress applied to the articular cartilage and the ability of the cartilage to withstand that stress, this may be due to:
1. Increase stress; the stress= load/ unit area, the increased stress may be due to increased load or decreased area of contact as in varus knee or acetabular dysplasia. 2. Weak cartilage; as in old age, chronic inflammation, or crystal deposition so the cartilage will breakdown easily.
3. Abnormal support by subchondral bone; which may be soft as in osteonecrosis providing inadequate support or the bone may be dense (fracture healing) so it become poor shock absorber.
Pathology; the pathological changes include: 1. Progressive cartilage disintegration and narrowing of joint space. 2. Sclerosis of the subchondral bone. 3. Subchondral cysts formation. 4. Osteophyte formation. 5. Capsular fibrosis.
Pathogenesis;
? Capsular fibrosis: the capsule become thick and fibrosed and may cause deformity. ? Increased intraosseous pressure: hyperaemia and venous congestion of the subchondral bone lead to increased intraosseous pressure that lead to night pain.
? Subchondral cysts: excessive fluid formation will increase the pressure inside the joint; the fluid will pass through cracks in the exposed subchondral bone leading to cyst formation.
? Synovitis: the synovium become thick &red.
? Osteophytes: secondary to cartilage damage the joint become unstable & the joint surfaces malaposed leading to new growth of the cartilage at the margin of the joint margins which ossify forming osteophyte.
? Subchondral sclerosis: the function of the cartilage is to distribute the forces at the joint surface & if the cartilage is damaged the force will concentrate on the subchondral bone leading to sclerosis.
Clinical features; The patient usually present after middle age one or two joints involvement (hip or knee) the major weight bearing joints, or there is involvement of the interphalangeal joints or involvement of any joint that have previous pathology. The patient complain from pain, typically the pain increased with activity & decreased with rest, the pain may results from stretching of the shrunked capsule or it is due to muscle fatigue, night pain is due to increased intraosseous pressure. The patient also complains from stiffness initially after rest then it become constant. There is loss of function. All these symptoms initially are intermittent with periods of remission then these symptoms become constant.
On examination, there is swelling of the involved joint, the swelling may be intermittent from effusion or it is continuous from capsular thickening & osteophyte. Also there may be deformity from capsular contracture or joint instability.
X-ray; the x-ray signs include (1) narrowing of the joint space (2) sclerosis of the subchondral bone (3) subchondral cyst (4) osteophyte (5)there may be evidence of previous disorder like congenital defect, rheumatoid arthritis, old fracture, chondrocalcinosis.
Treatment; it is depends on the stage of the disease:
? In early stage, it is conservative by physiotherapy to maintain joint mobility & increase muscle power. Also by load reduction by decreasing body weight avoiding activities like climbing stairs & using walking aids, the pain can be controlled by using analgesia like paracetamol & NSAID’s.
? In the intermittent stage, when the degeneration is localized to one compartment of the joint the patient can get benefit from realignment osteotomy this act by redistribution of the load to other area of the joint & by vascular decompression of the subchondral bone.
? In late stage, when the disease is advanced especially when the joint is stiff or unstable then arthrodesis or arthroplasty.
Osteochondritis (osteochondrosis)
It is a condition in which there is compression, fragmentation or separation of small segment of the cartilage & bone. It occurs in children & adolescent.
Pathology; the affected segment show ischemic necrosis with increase vascularity & reactive sclerosis of the surrounding bone.
Types; there are 3 types (crushing, splitting & pulling)
Crushing Osteochondritis It occurs in adolescent & typically affects the long bone ends & the cuboidal bones of the wrist & the foot.
Causes: may be abnormal anatomy with abnormal stress on the affected bone. Pathology; there is necrosis followed by fragmentation & new bone formation (sclerosis).
Clinical features; there is pain, local tenderness with limitation of movements.
X-ray; there is increased density, fragmentation then collapse of the affected bone. Examples;
? Freiberg’s disease; it affect the second metatarsal head especially if long, the treatment include shortening the metatarsal or excision the head.
? Kohler’s disease; affects the navicular bone, it causes pain in mid-foot, the x-ray show the navicular bone flat & dense, the treatment include arch support, the condition is self limiting.
? Kienbock’s disease; it affects the lunate causes pain & limitation of wrist movements, the x-ray show increase density, fragmentation, collapse & osteoarthritis. The treatment includes rest, splint &if OA occur then arthrodesis or excision of the navicular.
? Panner’s disease; it affects the capitulum due to long radius.
? Scheuermann’s disease; it is vertebral Osteochondritis, in which there is fragmentation of the vertebral epiphyseal plate leading to wedging of the vertebra & juvenile kyphosis, the treatment include spinal support & exercise.
Splitting Osteochondritis (Osteochondritis dissecans)
In this disorder a small segment of bone & overlying cartilage separated example femoral condyle, talus, capitulum, and first metatarsal head.
Pulling Osteochondritis (traction apophysitis)
It is due to excessive pull of the large tendon on any apophysis this occurs in tibial tuberosity (Osgood schlatter’s) & in the calcaneal apophysis (Sever’s disease).
Osgood schlatter’s; It is a self limiting disease causing pain & swelling over the tibial tuberosity, X-ray; show fragmentation of tibial tuberosity, treatment include rest avoid stress rarely excision of the loose fragment.
Sever’s disease; It affect the calcaneal apophysis due to traction by tendoachills, the x-ray show fragmentation & increased density, the treatment include rest, avoid stress, heel raise .