For the purposes of this discussion, the knee can be considered to have three compartments; the medial (close to the midline of the body), the lateral, and retropatellar (behind the knee-cap). Arthritis can involve any of the compartments in either isolation or combination. Meniscal tears (cartilage tears) can also be part of the spectrum of knee arthritis without having had a specific injury.
Surgical treatment for knee arthritis is considered after conservative measures have failed. NB osteochondral defects are not covered in this section. Options include total knee replacement (TKR), partial knee replacement (unicondylar or patellofemoral), and osteotomy.
Total knee replacement (TKR) involves replacing the entire tibiofemoral joint. The replacement takes the form of metal plates being placed on the tibia and femur, fixed in place with bone cement, with a plastic articulation in between. The patella is often, but not always, resurfaced, depending on the amount of damage seen at surgery and the specific TKR prosthesis used.
Partial knee replacements can be an alternative to TKR in a younger patient who has arthritis proven to be localised to one of the three compartments. The rationale is the patient makes a quicker recovery, and bone is preserved for the inevitable revision to a total knee replacement. This has not been proven to be the case in all patients, and Dr Shooter would only recommend this type of procedure in very special circumstances.
Osteotomy (HTO) involves cutting the tibia at the top (knee) end, to change the angle of the bone to protect a damaged compartment. It also requires that only one compartment be involved in arthritis, and the patient should be a young, otherwise fit and healthy active person with functional demands not able to be delivered by a joint replacement. Around 10% at 5yrs, and 35% at 10 years after surgery, require conversion to a TKR.
Recovery from TKR
Knee replacement may be performed using general anaesthetic (put to sleep), regional anaesthetic (epidural or spinal nerve blocks), or a combination of these techniques. Your anaesthetist will make recommendations about which technique best suits you.
You can place your whole body weight onto the knee and walk with assistance immediately after surgery. Hospital stay is usually 2-4 days; discharge is determined by when you are able to get your knee fully straight and bend it to ninety degrees. Crutches may be used for comfort a few weeks after the procedure and can be discarded when you are confident. Some people like to use a single crutch for a few weeks longer. Depending on your occupation, you will require 6-12 weeks off work. You are able to drive safely when you can walk comfortably. If you are a commercial driver or drive as part of your job, you may require a safety assessment by an occupational therapist prior to recommencing work.
Knee replacement surgery is very safe, and serious complications are uncommon. Serious wound infection occurs in less than 1%. Clots can form in the veins of the leg (deep venous thrombosis 'DVT'), which on rare occasions may dislodge and travel to the lungs causing breathing difficulty. To prevent this, you will be given an anticoagulant while in hospital, and you will continue this for 4-6 weeks when you go home
Recovery from HTO
Depending on the type of osteotomy done, you are usually restricted to partial weight bearing for the first six weeks after the surgery, and will need to wear a special type of knee brace. Hospital stay is usually 2-4 days; recovery and risks are otherwise very similar to TKR (see above).