Overuse, traumatic injury, and/or naturally occurring changes can lead to knee problems. Causes of knee pain include:
- Infection, tumors, or nerve problems (less common)
If you’re suffering from knee pain, contact us to learn about treatment options.
How Your Knee Works
The knee consists of four bones, the joints between them, the ligaments that keep things stable, and the muscles that generate strength and motion.
There are three major joints in the knee:
- The thigh bone (femur) stacks on top of the shin bone (tibia), creating the true knee joint.
- The outer lower-leg bone (fibula) bone runs parallel with the shin bone of the lower leg, forming the tibiofibular joint.
- The kneecap (patella) contacts the thigh bone in the front of the knee to form the patellofemoral joint.
The meniscus, a flexible rim of soft tissue, fills the space between the thigh and shin bones. The meniscus’ two C-shaped pieces help with stability and shock absorption.
The four main knee ligaments help provide stability but are commonly injured in sports or by trauma.
- The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) wrap around each other deep within the knee, attaching the thigh bone to the shin bone. They help prevent excessive pivoting of the knee and keep the shin bone from moving forward or backward under the thigh bone.
- The medial collateral ligament (MCL), which runs vertically along the inside of the knee, and the lateral collateral ligament (LCL), which runs vertically on the outside, help keep the knee stable side-to-side.
Three main muscle groups surround the knee joint and help power the knee for walking.
- The quadriceps muscles on the front of the thigh bone cross the knee over the kneecap, attaching to the shin bone via the patellar tendon.
- Hamstring muscles cross the knee on the backside of the thigh. Hamstring tendons attach on the fibula and the shin bone.
- Calf muscles attach to the heel in the back of the shin bone and run up the back of the lower leg, connecting behind the knee on the backside of the thigh bone.
Many other muscles play a role in the knee’s function and tracking of the kneecap, including the IT band and gluteal muscles – but muscles are just part of the story. Bones, joints, ligaments, and muscles must work in unison for the knee to function properly.
Certain knee conditions may require surgery – especially if conservative treatment hasn’t been successful. For example, an ACL tear often requires reconstruction to reestablish knee stability. Meniscus tears may also require surgery to remove or repair damaged tissue and keep the knee from catching or locking.
Some knee surgeries can be done with an arthroscope, where surgical instruments are inserted through two small incisions to make repairs. This causes less harm to healthy tissues and greatly reduces recovery time compared to traditional surgery.
Arthroscopic surgery can treat:
- Meniscus and ligament tears
- Cartilage damage
One arthroscopic knee surgery can often address multiple conditions.
After Knee Surgery
You’ll be asked to do ankle pumps right after surgery to help increase blood flow and prevent a blood clot from forming. This is important, since your activity level will decrease after surgery.
You’ll be placed on crutches until you regain full sensation in your knee. Before weaning off crutches, you should be able to bear full weight and walk comfortably. If more intensive work was done, you may need to use crutches for a few weeks and avoid placing weight on the leg.
It takes most patients four to six weeks before they’re back to daily activities; however, it can take six months to a year before they no longer notice knee pain.
Conditions Where Surgery May be Necessary
Your knee and patellofemoral joints are covered by smooth, hard cartilage. A cartilage defect or flap can cause a painful catch or click, limiting knee motion and making it hard to walk.
A damaged hard-cartilage flap can catch and damage healthy knee tissue. Relatively small defects can sometimes be smoothed and polished with gentle motion exercises, like using an exercise bike with no resistance, but surgery may be required for severe hard-cartilage damage.
A knee chondroplasty uses an arthroscope to remove fraying or flapped hard cartilage and smooth remaining tissue. You’re often put on crutches after this procedure and can wean from them at your own pace. Your surgeon will detail your post-surgery restrictions.
The thighbone and shinbone are stacked on top of each other and held together with tendons and ligaments. The anterior cruciate ligament (ACL) maintains knee stability by preventing the shinbone from moving forward in relation to the thighbone. Cutting and twisting place big demands on the ligament, and can cause ACL tears.
The ACL is one of the few ligaments in the body that doesn’t repair itself; it must be surgically reconstructed for the knee to regain stability.
An ACL reconstruction is an outpatient procedure done with a general anesthetic and a nerve block. This provides more initial pain relief after surgery.
Before your surgery is scheduled you’ll meet with your surgeon to talk over the procedure, its risks and benefits, and your questions or concerns.
To start the surgery, your surgeon makes two small incisions, one on each side of your kneecap, and uses surgical instruments to go in the knee and evaluate damage.
When you tear your ACL, one or both menisci are often damaged. These tissues, along with the ACL, are evaluated, repaired, or cleaned up. The notch in the end of the thighbone is sometimes widened to allow space for the new ligament.
ACL reconstruction is done using a ligament or tendon graft.
There are two types of graft:
- A donated ACL ligament from a cadaver (allograft), or
- Tissue from ligament or tendon from your own body (autograft)
An allograft ACL reconstruction involves less surgery and allows a quicker return to everyday activities. However, it takes a minimum of nine months before you can return to cutting and twisting-type activities.
If you’re returning to a sport or cutting and twisting-type activities are important, an autograft is typically used to reconstruct the ACL. Many tendons in your body can be used to reconstruct your ACL; however, the gold standard is to use the middle one-third of your patellar tendon, with a small piece of bone from your shinbone and kneecap.
Since an autograft involves more surgery, the initial recovery is slower and you may be on crutches a bit longer than allograft surgery. However, with autograft ACL reconstructions you can return to cutting and twisting activities, including sports, as soon as six months after surgery.
Regardless of the graft choice for ACL reconstruction, a hole is drilled through your shinbone and thighbone and the graft is placed with a screw made of a bone-like substance.
After the graft is in place, your surgeon will move your knee around to make sure the newly reconstructed ACL is in the correct location and is tight without pinching. If an autograft was used, the incision is closed and a local anesthetic injected for initial pain control.
After this procedure, you’ll be on crutches but can wean off of them as you’re able to tolerate weight – typically one to three weeks. You’ll begin physical therapy a day or two after surgery. Your therapist will help determine when you’re ready to walk without crutches. The Wisconsin Performance Institute’s ACL-PRO Program is designed to get patients back to sport or activity as quickly and safely as possible. The WPI uses an exclusive combination of high-tech motion analysis and directed, personalized physical therapy.
Between the thigh and shin bones is the meniscus – two C-shaped pillows of soft cartilage that absorb shock, increase stability, and lubricate the knee.
The meniscus is often injured by twisting movements in a squatting position, like lifting a box or misstepping on uneven ground.
The meniscus can fray or completely tear, causing a tissue flap to catch within the knee joint. Sometimes a piece of the meniscus can flip up and cause the knee to lock, or cause pain, popping, or a feeling of instability in your knee.
Removing the fraying or flapped meniscus arthroscopically and smoothing remaining tissue can fix this issue. After a meniscal debridement you’re often placed on crutches and can wean from them at your own pace.
Your surgeon repairs a completely torn meniscus using sutures with anchors to fasten the meniscus to the joint capsule. The number of sutures depends on the size and severity of your injury.
After a meniscal repair your surgeon will give you specific instructions and post-surgery restrictions, but expect to use crutches for about six weeks after surgery.