A meniscus is a "cushion" made of cartilage. Our knees contain two of these cushions. They sit side by side, between the thigh bone (femur) and the top shelf of the shin bone (tibia). These cushions are normally crescent-shaped, like flattened kidney beans. They absorb shock and spread out forces inside the knee joint by improving contact between the thigh and shin bones. They also add stability to the knee joint when we stand and move. The meniscus on the inner side of the knee (nearest the other leg) is larger than the one on the outside of the knee, which is typically smaller and rounder. Both of these cushions are attached to the shin bone at the front of the knee. The outer cushion is also attached to the thigh bone by a ligament at the back of the knee.

A discoid meniscus occurs when the cartilage in the knee does not properly develop while a baby is still in the womb. The result is a thicker, more saucer-like or oval-shaped meniscus. It occurs most often on the outer cushion of the knee joint. The abnormal structure and thickness puts the cartilage at a higher risk for injury, such as tearing. Since cartilage is not capable of healing itself after injury, surgery is often required for repair.

There are three types of discoid meniscus:

• Incomplete (type I).The shape of the meniscus is wider and thicker, but still covers less than 80% of the outer shelf of the shin bone. Its attachment to the ligament is normal.
• Complete (type II). The shape is significantly wider than normal, covering the entire outer shelf of the shin bone. The ligament attachment is normal.
• Wrisberg variant (type III). The shape of the meniscus is normal, but the ligament attaching it to the back of the knee is missing. This leaves the meniscus unstable or too mobile. This type can result in the sudden feeling of snapping, clicking, or catching during movement of the knee.

Meniscal injuries most commonly occur in activities that require sudden stopping, pivoting, and turning that require the body to move over or around a planted foot. For people with a discoid meniscus, a tear can occur even without a specific injury or event.

Many people with a discoid meniscus will never have any symptoms that affect their movement or cause discomfort. Children often have no signs or symptoms up to the age of four years. Symptoms typically arise around eight to 10 years of age but can begin sooner. Once symptoms occur, surgery is the recommended treatment. The goal of surgery is to either reshape the meniscus or repair it if it is torn.

When a discoid meniscus tears or begins to cause problems, you may experience:

• Pain in the knee, most often on the outer or front side.
• Sharp pain with running, jumping, cutting, or deep squatting.
• Swelling in the knee.
• Tenderness on the outer side of the knee.
• Catching, locking, or popping feelings inside the knee while walking or squatting.
• Loss of knee motion. In particular, the knee gets "stuck” while trying to fully bend or straighten.
• Loss of strength/weakness in the thigh muscle.
• Discomfort with daily activities, like walking up and down stairs.

Diagnosis begins with a detailed medical history and physical examination. A physical therapist can assess your knee by measuring:

• Movement.
• Strength.
• Flexibility.
• Tenderness.
• Swelling.

This can include tests to rule out or rule in an injured meniscus. Your physical therapist also will ask you to describe activities or positions that cause your pain, such as walking, squatting, and stepping up or down stairs.

If your physical therapist suspects a discoid meniscus (or other knee joint injury), they will refer you to an orthopedic doctor (a bone and joint specialist) for X-rays or an MRI. These tests will confirm whether you have a discoid meniscus or a tear in your meniscus that needs repair. If confirmed, and your symptoms affect your daily life, surgery is the recommended treatment.

Before surgery, your physical therapist will work with you to develop a plan to achieve your specific goals and address your symptoms. Physical therapy may start by helping to relieve your pain, strengthen your muscles, and prepare for surgery. Physical therapy will resume after surgery to help you return to your regular activities. Your treatment program may include:

Joint range-of-motion exercises. Any injury or surgery causes a joint to be irritated. This often results in swelling, stiffness, and loss of normal motion. While it is important to regain your normal motion, it is also vital to allow your injury to heal without placing too much stress on the affected joint. Your physical therapist will assess your motion, prescribe gentle exercises, and create a plan to balance joint protection and function.

Strength training. Your physical therapist will teach you exercises to strengthen the muscles around your knee. These exercises will help each muscle properly perform its job with ease while the joint is protected.

Manual therapy. Physical therapists are trained in (manual) hands-on therapy. If needed, your physical therapist will apply hands-on techniques at your knee cap (patella), tendons, and surrounding muscles. This treatment will help improve motion, flexibility, and strength. These techniques target areas that are difficult to treat on your own.

Swelling and pain management. Your physical therapist will apply pain-relief treatments by identifying specific movements or activities that aggravate and relieve your symptoms. Your physical therapist will then design a personalized treatment plan for you. This plan may begin with a period of rest, and will add exercises and treatments when appropriate to gradually help you return to daily activities.

Functional training. Physical therapists are experts in movement training, balance, and coordination. Your physical therapist will assess your movements and teach you to adjust them to relieve stress on your knee.

Education. Your physical therapist will work with you to identify and change any factors causing your pain. These may include exercise selection, footwear, or the amount of exercise you do. Your physical therapist will develop a personalized program to help you return to your desired activities.

A discoid meniscus is present at birth and, therefore, cannot be prevented. There is no known cause for this condition. Maintaining lower-body mobility and muscle strength are the best methods for preventing any type of knee injury.

The structure of some people's menisci will increase the risk of injury. It is important to be aware of any knee pain you experience, particularly with squatting, running, or turning. Pain during these movements are signs of a potential knee injury. Addressing these injuries early is helpful in both treatment and long-term outcomes.

All physical therapists are prepared through education and clinical experience to treat a variety of conditions or injuries. You may want to consider:

• A physical therapist who is experienced in treating people with orthopedic or musculoskeletal injuries.
• A physical therapist who is a board-certified specialist, or has completed a residency in orthopedic, sports, or pediatric physical therapy. This physical therapist will have advanced knowledge, experience, and skills for this condition.

You can find physical therapists who have these and other credentials by using Find a PT, the online tool built by the American Physical Therapy Association to help you search for physical therapists with specific clinical expertise in your geographic area.

General tips when you're looking for a physical therapist (or any other health care provider):

• Get recommendations from family, friends, or other health care providers.
• When you contact a physical therapy clinic for an appointment, ask about the physical therapist’s experience treating knee pain.
• Be prepared to describe your symptoms in as much detail as possible and report activities that make your symptoms worse.