SPONTANEOUS OSTEONECROSIS

In separate chapters we’ll discuss arthritis. Whereas arthritis is a gradual degenerative condition, which develops over months or years, spontaneous osteonecrosis has sometimes been described by patients as “instant arthritis.” It is a more common problem for older individuals, with the average patient about sixty-five years old, although the range is from forty to eighty-five. We really don’t know what causes this condition, but its typical presentation is a real attention-getter.

Symptoms

A sudden, severe pain, rarely associated with trauma of any sort, occurs spontaneously. If you’ve experienced this pain, you probably remember exactly what you were doing when the pain struck. The pain most often occurs on the inner side of the knee. It is not improved by rest, and weight-bearing activities, such as walking, may aggravate the pain. lt does not subside with time. During this early phase the knee appears “locked” because it’s prevented from complete extension or flexion due to pain, effusion, and muscle spasm. It’s not a true “locked” knee because there is no mechanical block, although a mechanical block does sometimes develop.

The future isn’t bright for those knees struck with spontaneous osteonecrosis. Although for a few lucky people the pain will subside in three to six months, others will continue to experience degenerative changes within their knee, causing pain and a limiting of function. This may occur rapidly, although the typical case develops slowly. The prognosis is sometimes dramatically poor and rarely good.

During the first four to eight weeks X rays are normal, then sometime between two and six months changes are often noted by X rays.

Treatment

If diagnosed early, pain medication is best, along with crutches or a cane and at least six months of isometric quadriceps exercises. Although the threat of continued arthritic-type changes is great, the majority of patients seem to respond to this conservative approach.

Unfortunately, S.O. victims sometimes show (in X rays) a lesion actually creating a growing crater along the inner ends of the femur and tibia. If major problems persist and there is increasing deformity one to three years following the onset of symptoms, surgery, ranging from arthroscopy to a total knee replacement, may be necessary. The best success, in chronic cases, is seen with a high tibial osteotomy. That may sound like a religious ceremony, but what it means is that by removing a wedge of bone on the lateral, or outer, side of the knee, the knee undergoes a realignment. This has the same effect as realigning a car’ s tires: lt corrects the alignment problem caused by the lesion and takes the load off of the injured bone by transferring it to another part of the knee.