In broad terms arthritis can be divided into inflammatory disease (this includes autoimmune disease or rheumatic disease), post-traumatic disease or overload syndromes where for some reason the joint is loaded abnormally and causes arthritis in the overloaded portion of the joint. This phenomenon is apparent in all joint of the body but most obvious in the knee. When arthritis is caused by overload syndromes it may sometimes be possible to offload a joint by performing various sorts of osteotomies (bone cuts) around the joint. This may have to be coupled with various soft tissue procedures to ultimately bring the joint back into alignment. The osteotomies around the knee involve the patello-femoral joint or the tibio-femoral joint. In general the results of the procedure are reasonably expected to bring pain relief in a properly selected patient. One who is younger and fitter with a higher demand on the knee. It is not appropriate when the disease is advance or when more than one joint is involved (ie. it would be ill-advised to do both procedures in the same knee).
In this procedure 4 procedures are potentially done around the knee in various combinations depending on the indication (Figure 1).
1. If there is tightness in the outside of the knee a lateral release of the muscles is done
2. If there is poor development of the patella in its groove on the femur a muscle advancement on the inner thigh is performed.
3. If there is high pressure on the knee cap the patella is elevated by raising the tibial tubercle.
4. If there is a tendency for the patella to flop off the femur on the outside the tibial tubercle is pushed inwards.
Similarly related to this condition is patello-femoral dislocation. This is a very common condition predisposed to by laxity of ligaments. Therefore it typically occurs in teenage girls and young women. The best time to treat these successfully is in the acute phase when a cast is placed. This would allow the medial structures like the vastus medialis obliquus (VMO) muscle to heal and scar in a position that holds the patella in place. In a deeper plane is the medial patello-femoral ligament (MPFL) which tears. This too can be held in place with a cast for 6 weeks. Following this period however whatever scar that forms is permanent and it is unlikely that any form of bracing will suffice. Therefore, if recurrent dislocation persists, the procedures mentioned above are evaluated for. If however all structures mentioned in 1-4 are normal, then an MPFL ligament reconstruction alone is considered (5). It should be stressed that in cases where an MPFL reconstruction alone is performed failing to recognize the inherent malalignment some patients have, the procedure is known to fail.
Figure 1. Soft tissue realignment procedures around the knee to restore patella tracking and a case of MPFL injury after an acute patellar dislocation (right)
In the case illustrated below (Figure 2) the patient had tightness on the outside (a), with a tilt and arthritis had begun (b). A lateral release and tibial tubercle elevation and medialization using a bone block spacer was performed. Six months later, the patello-femoral joint was re-established (c), the patello-femoral joint was more aligned and the bone block had incorporated well (d).
In the bow-legged (varus) knee, there is increased load on the inside of the knee. This predisposes to arthritis on the inside of the knee (e). To reduce the load a wedge of bone is removed from the tibia and the tibia realigned to re-distribute the forces on the outside of the knee (f).
Figure 2. Bony realignment procedures done around the knee to restore normal knee function