Other Knee Conditions

Baker’s (Popliteal cyst)

Sometimes there is swelling mainly in the back of the knee, and it may even be the first thing you note that is wrong with the knee. The cause is whatever is causing the synovitis and production of excessive synovial fluid within the knee. Generally, once that underlying cause is identified and fixed, the Baker’s cyst goes away by itself. Very occasionally, the cyst may have become so big and thick that it can’t resolve, and that it continues to cause sufficient trouble for it to be surgically removed. That requires a fairly small open operation, but it cannot be done with just an arthroscopy.

Osteo-Chondritis Dissecans

This is an unusual condition that develops in the last few years of growth, and is thought to occur because a small segment of the joint surface loses its blood supply long enough, or repeatedly enough, to become separated from the main body of the bone. The joint surface (articular cartilage) remains intact for a few months to several years, but when it splits around the margins of the lesion, the fragment of bone and articular cartilage separates and becomes an osteo-chondral loose body. This may click and cause discomfort and/or swelling. It may also dislodge and get jammed between the bones causing episodes of locking.

The treatment is either to replace the fragment back in the crater it came from, and try to get it to heal, or if it is thought that is not going to succeed, or has already failed, then to just remove the loose body. That still leaves the question of the crater. If it is quite small, no further treatment may be necessary. If, on the other hand, the remaining crater is large enough to cause ongoing symptoms, or if it is lie that early arthritis will result, then it is desirable to find another way of trying to heal the defect. The most popular technique these days is to take some of the healthy articular cartilage from the joint, culture it in the lab for about 6 weeks, and then do what is called an Autologous Chondrocyte Impantation (ACI). If, as is usually the case these days, the graft comes on a collagen patch (matrix), then it is called Matrix Autologous Chondrocyte Impantation (MACI).

Osgood Schlatter’s Disease

Not really a “disease” at all, this an over-use condition of the knee that occurs in kids whose skeleton has not yet matured. The over activity puts excessive load through the patella tendon, going from the knee-cap to the top of the shin, resulting in a traction injury to the growing bone at that point. The result is pain with and after activity, and tenderness right at that spot (the Tibial Tuberosity), and often the bone is slightly lifted up resulting the development of a permanent lump. The pain usually resolves by itself with reducing activity, and finally when the kid stops growing. Sometimes however, by that stage, a small fragment of bone may have become separated, forming an ossicle in the attachment site of the tendon, and where that attaches to the main bone may become a source of ongoing pain with activity. In that case it is called unresolved Osgood Schlatter’s disease, and it may be worth excising the ossicle. There will still be a lump though, because of residual scar tissue.

Patella Tendonitis (also called jumper’s knee)

This is the over-use condition affecting the patella tendon, going from the knee-cap to the top of the shin, that occurs after skeletal maturity, as opposed to Osgood Schlatter’s disease (above), which occurs in youngsters. The pain occurs at the top end of the tendon, at the lower end (inferior pole) of the knee-cap, and is due to micro-tearing of some of the deeper fibres of the tendon where they attach. Treatment is usually successful with physiotherapy, focusing on stretching exercises for the quads and hamstrings, machine and massage treatment to the site of pain, and anti-inflammatories and some rest to get the pain to settle initially. Sports doctors can often help with different treatments aiming at increasing the blood supply and healing potential of the micro-tear. Cortisone injections and even surgery may be required if all else fails.

Pre-Patella Bursitis (House-maid’s knee)

There is a thin lubricating sack that allows the skin over the front of the knee to glide over the surface of the knee-cap. If that gets inflamed and swollen, it looks like the knee itself is swollen, and sometimes red, but on closer inspection, there is no excess fluid in the knee itself. All the swelling is in front of the knee-cap, and can cause trouble with kneeling, and with wearing trousers that rub over the area. In the early stages this can settle with anti-inflammatories and avoidance of aggravation. The next step would be a cortisone injection, and if all else fails, and it is giving a lot of trouble, then the swollen bursa can be excised.

Pigmented Villo-Nodular Synovitis (PVNS)

This is a rare and strange condition in which the synovium (soft joint lining inside the capsule) becomes severely inflamed, and can be very lumpy (nodular) or diffuse (villous) or both. It may be throughout the knee (or any other joint), or localised to one small area. It can be very aggressive and grow into bone, and grow back when it has been excised. Despite that, it is not a form of cancer, and does not go anywhere else in the body. If it is an isolated nodule, it usually does not recur. If the diffuse type does recur, it may require some follow-up radiotherapy the next time it has to be excised.

Tribio-Fibular Joint Synovitis/arthritis

The Tibio-Fibular joint at the knee (there is also a tibio-fibular syndesmosis at the ankle) is a small and often forgotten joint on the outer side of the knee. It doesn’t do much really, except allow for some minor rotation of the fibular, which is the thinner of the two bones in the leg below the knee, the main purpose of which now seems to be for muscles to attach to. Although the joint is not functionally important, it often communicates with the knee joint, and occasionally can be a problem in its own right, with or without problems also occurring in the knee joint. If pain is particularly on the outer side of the knee, it is one of the possible causative factors. If the problems within the knee joint have been fixed, maybe with an arthroscopy, or maybe after a knee replacement, and lateral pain persists, it is worth getting it checked with a bone scan, or an MRI, or both. A cortisone injection may be enough to settle the joint down again, or at least give temporary relief. If the pain should recur after good initial relief, it confirms that that is the problem. If all else fails, the joint can be excised and/or fused, which usually solves the problem very well and permanently.