The knee is a complicated joint that consists of the femur (thigh bone), the tibia (shin bone), and the patella (knee cap). Between these bones there are multiple ligaments and soft tissue elements which can have various types and injuries and disease.
The most commonly injured component is the meniscus which serves as a shock absorber between the femur and tibia. The meniscus is often torn during the a twisting motion to the knee which can cause pain, locking, and catching in the knee. An MRI is used to determine if this is the case. If no improvement is seen with therapy and time then consideration can be given for arthroscopic surgery to remove the torn fragments. This entails two small holes (about 5mm each) in the front of the knee to put in a small camera to remove any fragments.
Older patients tend to develop arthritis in the knee which means the smooth articular cartilage of the knee is worn away and femur and tibia bone grind on each other causing severe pain. Conservative care would entail weight loss, strengthening of the quadriceps muscles through physical therapy, anti-inflammatory medications, and injections. There are two types of injections that can be given. One is a steroid injection which has been the mainstay of treatment for over 25 years. The other is a hyalgan injection which is a viscous gel that acts as a type of lubricant in the knee. Diffferent patients respond differently with each type of injection. Stem cells are also an option for injection into the knee. I generally recommend these options before recommending surgery.
Failing conservative care, surgical considerations can be given. Knee arthroscopy is a minimally invasive surgery performed with two small 5mm incisions. We are able to look in the knee and assess the issues. Torn meniscus or cartilage can be removed which may help with knee pain. If the arthritis in the knee is the main issue, then knee replacement can be considered. Knee replacement entails removing the destroyed cartilage at ends of the femur, tibia, and patella and cementing metal components into each bone with a specialized plastic material between them.
This is a cartoon demonstrating the femur, tibia, and patella bones and the meniscus in between them acting as shock absorbers.
This is a cartoon denoting the wearing away of the smooth articular cartilage down to the bone. The nerve endings in the bone rub with weight bearing and can cause significant pain.
Normal Knee X-ray
This is a normal knee x-ray. Note the space between the femur and the tibia. This is articular cartilage which does not show up on x-ray which is why it is black.
Arthritis Knee X-ray
This is an X-ray showing severe knee arthritis. This is "bone-on-bone" arthritis on the medial (inside) aspect of the knee. The knee is also no longer straight but in varus (crooked) alignment. After surgery we correct the alignment and staighten out the knee.
Knee Replacement X-ray (AP)
This is an immediate post-operative knee replacement X-ray. The ends of the arthritic cartilage on the femur and tibia have been removed and metallic implants have been cemented in place, with plastic in-between.
Knee Replacement X-ray (Lateral)
This is the side (lateral) view. This is a DePuy rotating platform design which allows rotation of the tibia much like a natural knee. It was originally designed for younger patients but I use in all of my patients.