Knee Surgery • M|M Orthopaedics

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Knee pain and injury can significantly limit your ability to move, work, and stay active. Whether caused by sports, aging, or trauma, untreated knee conditions can worsen over time and impact your quality of life.

At our practice, we specialize in advanced, personalized orthopedic care for a wide range of knee conditions. Our goal is simple: restore function, reduce pain, and help you return to the activities you love.

Led by fellowship-trained, board-certified orthopedic surgeons, we offer comprehensive evaluation and treatment plans tailored to each patient’s unique anatomy, lifestyle, and goals.

The knee is one of the largest and most complex joints in the body, connecting the thigh bone (femur) to the shin bone (tibia), with the kneecap (patella) providing additional support and movement mechanics.

A network of ligaments, tendons, cartilage, and fluid-filled bursae work together to stabilize and cushion the joint:

ACL (Anterior Cruciate Ligament) prevents forward instability of the tibia
PCL (Posterior Cruciate Ligament) prevents backward instability
Collateral ligaments stabilize side-to-side motion
Meniscus cartilage acts as a shock absorber between bones

When any of these structures are damaged, pain, swelling, instability, and limited mobility can result.

ACL Tears

The ACL is one of the four major ligaments in the knee joint. It is located deep and central in the knee connecting the femur (thigh bone) to the tibia (shin bone). The ACL is a ligament in the front part of your knee. It works with the PCL, which is in the back, to keep your knee stable and help it move properly. ACL repair is a type of surgery where doctors try to reattach your own ACL back to the bone. This method is only used for a specific kind of ACL tear and is different from ACL reconstruction, which is a more common surgery. ACL reconstruction is a surgery that helps replace a torn ACL, which is an important ligament in your knee. For the majority of young and/or high-level athletes we tend to use their own tissue known as autograft, as opposed to allograft (tissue from a donor). Patients always want to know which graft is the best, but it is important to understand that there is no perfect graft to replace your ACL. Each graft has advantages and disadvantages. All three autografts have shown success in intermediate and long-term studies with relatively low failure rates. We offer Revision ACL surgery to fix problems that remain after a previous ACL surgery.

Knee Osteoarthritis

Osteoarthritis (OA) is the most frequent form of arthritis that impacts the knee. It is a result of breakdown of cartilage. Cartilage is the coating on the end of the bone that protects the joint and decreases friction. OA leads to stiffness, swelling and joint pain. It makes everyday activities like kneeling, climbing stairs, and walking difficult. Some people with knee osteoarthritis (OA) live their lives without even realizing they have it, and they don’t feel any knee pain. But if you start having symptoms of knee arthritis, you can choose treatments that help with the pain or address both the pain and the problem in your knee. Non-surgical treatment options include changing your daily activities, medications, and physical therapy. Usually, if you follow these treatments, your symptoms should get better within a few weeks. If your knee pain improves and you can get back to doing the things you enjoy, you might not need any surgery. If non-surgical treatments for knee arthritis don’t help with your pain and tests show that you have knee osteoarthritis, surgery might be a good option. The main type of surgery for knee osteoarthritis is knee replacement surgery. This can be either a partial knee replacement or a total knee replacement.

Knee Arthrofibrosis

Knee arthrofibrosis is a condition where too much scar tissue builds up inside the knee joint. This extra scar tissue can make your knee feel stiff and less flexible. It can also stop the knee from moving smoothly. Sometimes, you can treat knee arthrofibrosis without surgery, especially if it’s been 2-3 months after knee surgery. You can manage it with rest, avoiding aggravating activities, medication, physical therapy, injections, and home devices for bracing. If your knee is still very stiff and doesn’t improve with non-surgical treatments, surgery might be needed. The main surgery for a stiff knee is called knee arthroscopy with lysis of adhesions (LOA) and manipulation under anesthesia (MUA). Here’s what happens during this surgery: Arthroscopy: The doctor makes 2-3 small cuts in your knee and uses tiny tools to remove extra scar tissue. Manipulation Under Anesthesia (MUA): While you’re asleep, the doctor moves your knee around to break up any remaining scar tissue and help restore movement.

Knee Cartilage Injuries

A cartilage injury is when there’s damage to this smooth coating layer, similar to chipped paint on your walls. This kind of injury can happen to anyone, but it’s more common in people over 40 and can also affect younger people after accidents. Many people can live with cartilage defects without pain. If symptoms do show up, you can manage them without surgery by keeping body weight at or near your ideal weight, changing activities to avoid pain, doing physical therapy, taking over-the-counter anti-inflammatory medicine, getting injections to relieve pain. If these methods work, surgery might not be needed. If pain continues, you have recurrent swelling or if the knee locks, surgery might be necessary. One way to fix cartilage damage is with a procedure called an osteochondral autograft transfer (OATS). This surgery involves taking a small piece of bone and cartilage from a less important area of the knee (where it doesn’t bear as much weight) and moving it to the damaged area. This helps repair the cartilage and reduce pain. The procedure is usually done using arthroscopy, a minimally invasive procedure using a camera and small incisions. The damaged area that needs the graft is usually around 1 cm in size or smaller. This size helps reduce problems at the site where the tissue was taken from. An osteochondral allograft is a piece of cartilage and bone taken from a donor. The surgery to put this graft in requires a small incision to access the knee joint. Sometimes, larger incisions are needed, depending on where the damage is. Matrix-induced autologous chondrocyte implantation (MACI) is a surgery used to repair cartilage damage in the knee. It uses a patient’s own cells to help regenerate new cartilage. This procedure is used to treat full-thickness cartilage defects, meaning the cartilage is completely damaged or worn away. MACI is especially helpful for people who have pain but no bone loss or severe cartilage degeneration. It is the first FDA-approved treatment of its kind and works by using the body’s own healing process to restore damaged cartilage.

Knee Malalignment

Your knee joint is made up of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). Imagine a line going straight down your leg from your hip to your ankle. This line helps us understand how your leg bones should line up. Keeping your leg bones in line along this imaginary line is important for normal movement and to prevent problems. Knee malalignment happens when your knee isn’t in its normal position along this line. There are two main types of knee malalignment, Genu Valgum (Knock-Knees) and Genu Varus (Bow-Legged). Both of these problems can affect how your knee moves and may increase your risk of injuries or conditions like arthritis over time. When treating knee malalignment, doctors often start with non-surgical methods. These treatments focus on reducing pain, swelling, and inflammation, while also helping the knee function better and stay stable. Symptoms can be managed non-surgically with rest, activity modification, medications, physical therapy, knee braces, and injections. If non-surgical treatments don’t work for knee malalignment, surgery might be the next step. Dr. Mehran and Dr. Muffly may suggest a procedure called an osteotomy to fix the alignment of the knee. Osteotomy procedures often are done with several other procedures such as meniscal transplantation or ligament reconstructions. Dr. Mehran and Dr. Muffly believe that there is nothing more important than patient outcomes. For this reason, they generally perform these complex procedures with a two-surgeon approach to cut down the time of surgery decreasing infection risks and time under anesthesia. Additionally, for osteotomies they use advanced technology that makes the plate and instrumentation specific to each patient instead of using a more generic approach of general plates and instruments. They strongly believe this technique is more minimally invasive and can lead to better results.

Knee Pain

Knee pain can be really uncomfortable and might cause other problems like walking oddly or back pain. It can make it hard to do everyday activities or play sports. If your knee pain lasts more than a couple of weeks or is really bad, you should see a doctor for a check-up. When you first visit us, we usually take x-rays to look at the bones in your knee. After that, we do a physical exam to find out where the pain is coming from. Sometimes, we might need more tests like an MRI or CT scan to get a better idea of what’s wrong and decide on the best treatment.

Knee Tendinitis

Tendinitis of the knee is when the tendons around the knee get inflamed or irritated. Tendinitis usually happens because of repetitive stress on the knee, such as overusing the knee with activities like running or jumping, poor technique or muscle imbalances, or wearing improper footwear. Knee tendinitis can often be treated without surgery by changing your activities, taking medications, physical therapy, wearing supportive gear, and shock wave therapy. Typically, symptoms improve within 6 months with these treatments. If these methods don’t work, surgery might be needed.

LCL Tears

The lateral collateral ligament (LCL) is a strong band of tissue on the outside of the knee. It connects the femur (thigh bone) to the fibula (a smaller bone in the lower leg). The LCL helps keep the outside of the knee stable and prevents it from opening up too much when force is applied to the inside of the knee. The outer part of the knee, known as the posterolateral corner, includes the LCL, the popliteus tendon, and the popliteofibular ligament. These three parts work together to stabilize the knee. Think of the LCL like a cord that keeps the knee from opening up too much on the outside. Most LCL injuries, especially if they also involve other knee ligaments, usually need surgery to fully heal because the knee’s structure is naturally unstable when the ligaments are damaged. The thighbone and shinbone in the knee are round, which makes it hard for this part of the knee to stay stable without proper support. If you have a complete tear of the LCL or other parts of the posterior lateral corner (PLC), it’s best to get surgery within the first two weeks after the injury, once you have some range of motion back. This early surgery is important because it helps fix the knee before scar tissue forms and the tissues get weaker. It also helps ensure that the knee is aligned correctly rather than healing in a wrong position. However, if someone only has an isolated LCL injury (where the LCL is hurt but not other ligaments), surgery might not be necessary. Instead, you can try non-surgical treatments depending on how bad the injury is. To treat an LCL injury without surgery, you should rest, avoid painful movements, take medications, wear a brace, and get physical therapy. Usually, symptoms will get better within 2 to 4 months with these treatments.

MCL Tears

The Medial Collateral Ligament (MCL) is a ligament on the inside of your knee that helps keep it stable. It connects the thigh bone (femur) to the shinbone (tibia) and prevents the knee from bending too much outward (valgus stress) leading to a sensation of knock knees. Along with the MCL, the posterior oblique ligament (POL) is also important for stabilizing the knee. The MCL helps when the knee is slightly bent (20 to 30 degrees), while the POL works when the knee is almost straight. Together, these ligaments keep the knee stable throughout its movement. Most MCL injuries can heal on their own without surgery. The MCL is well-supplied with blood and nutrients, which helps it heal. It’s also located outside the knee joint, where it’s less affected by the proteins in joint fluid that can slow down healing. To treat an MCL injury without surgery, you should avoid painful movements, take medications, wear a brace, and get physical therapy. Usually, symptoms will get better within 2 to 4 months with these treatments. If you have a complete tear of the MCL (Grade 3) or if multiple structures in the inner part of your knee are injured, surgery might be necessary. It’s best to have the surgery within two weeks after the injury, once you have regained your range of motion. Doing the surgery early helps prevent severe scarring and keeps the knee in the correct position, which leads to better recovery.

Meniscus Tears

The menisci are two C-shaped pieces of cartilage that sit between the femur and tibia in each knee. They act like shock absorbers, helping to cushion the knee and keep it stable. They also help distribute the pressure they encounter evenly across the knee joint, which protects the knee from damage. Some people with meniscus tears don’t even realize it because they don’t have any pain. Depending on the type and severity of the tear, many meniscus injuries can be treated without surgery. The main goal of non-surgical treatment is to reduce pain, swelling, and inflammation, while also improving knee stability and function. To treat meniscus tears without surgery, you should rest, avoid painful movements, take medications, ice the knee, wear a brace, and get physical therapy. If pain and swelling continue despite non-surgical treatment, or if you have specific types of tears like root, radial, or bucket handle tears, surgery might be needed. Arthroscopic surgery is a common procedure where a small camera is inserted into the knee joint through a tiny incision. The doctor looks at the meniscus and then decides whether to repair, trim, or remove the damaged part. Other small tools are used to do the repair or trimming. This type of surgery is minimally invasive, meaning it causes less damage and has a quicker recovery time. It’s usually done in an outpatient center with general anesthesia. A meniscus transplant is a surgery to replace a damaged or missing meniscus with one from a donor (someone who has passed away). It’s typically used for more complex or severe knee injuries, especially when much or all of the meniscus has been removed. The goal is to restore function, improve stability, and reduce pain in the knee. A discoid meniscus is an abnormally shaped, disc-like cartilage in the knee, usually on the outer side, that can cause pain when it tears. Treatment typically involves surgically reshaping or partially removing the damaged tissue (saucerization), though repair is sometimes possible if the meniscus is still healthy and has a blood supply. Because removing too much meniscus increases the risk of arthritis, ongoing monitoring and follow-up care are important after surgery.

Multi-Ligament Knee Injuries

A multi-ligament knee injury occurs when two or more of the knee’s stabilizing ligaments are damaged, including the ACL, PCL, MCL, and LCL, which control forward-backward and side-to-side stability. These injuries can also involve smaller supporting ligaments that help control rotation and overall knee alignment. In severe cases, such as a knee dislocation, multiple major ligaments are torn, creating significant instability and sometimes risking damage to nearby blood vessels and nerves, making it a medical emergency. Multi-ligament knee injuries usually don’t heal on their own. Since these injuries make the knee very unstable, surgery is often needed to restore knee function and stability. Surgery is usually recommended within the first two weeks after a knee dislocation, if the knee has a good range of motion. Trying to operate on a stiff knee can make the surgery less effective. For patients with a good range of motion and no additional problems, surgery is done to repair the torn ligaments and menisci. Surgery for a multi-ligament knee injury is serious. It’s best to repair all the damaged ligaments and menisci in one surgery to avoid over-stressing any one area.

Osteochondritis Dissecans (OCD)

Osteochondritis dissecans (OCD) is a condition where a small piece of cartilage and the bone underneath it detach from the joint surface. This usually happens because that part of the bone and cartilage doesn’t get enough blood supply. Blood flow provides the necessary nutrients to the bone and joint to help it thrive. Without proper blood flow, the tissue can weaken and separate. Non-surgical treatment for OCD of the knee focuses on relieving symptoms and supporting healing. This may include reducing or avoiding weight-bearing, rest, ice, medications, physical therapy, bracing, and occasionally injections to help with pain and swelling. If symptoms persist, surgical treatment may be needed to restore knee function and address the damaged cartilage. Options include arthroscopy to evaluate and treat the lesion by smoothing, repairing, or stimulating healing, and in more advanced cases, cartilage restoration using either donor tissue (allograft) or the patient’s own cartilage (autograft).

Patellar Instability

The patella, or kneecap, is a small bone that sits in a groove (the trochlea) at the end of the thigh bone (femur). It slides up and down as the knee bends and straightens. Several ligaments and structures help keep the kneecap in the groove. Sometimes, the kneecap can slip out of its groove, causing pain, swelling, and stiffness. This condition is known as patellofemoral instability (PFI). It often happens due to a sports injury, a fall, or a direct hit to the knee. Non-surgical treatment for patellar instability is often used for new or mild cases. It typically includes physical therapy to strengthen the muscles around the knee and a brace to help stabilize the kneecap and prevent it from dislocating again. Surgical treatment may be needed if instability is severe, recurrent, or causing ongoing pain or damage. Options depend on the underlying cause and may include ligament reconstruction (MPFL/LPFL), bone realignment (osteotomy), deepening the kneecap groove (trochleoplasty), cartilage repair, or arthroscopy to address loose tissue and improve stability.

Patellar Tendon Tears

The patellar tendon is a strong, flat band of tissue that connects the kneecap (patella) to the shinbone (tibia). It is a key part of the knee joint, helping to straighten the leg and allowing you to stand, walk, run, and jump. A patellar tendon rupture is when the patellar tendon tears off the bottom of the kneecap, either completely or partially. This injury affects the tendon that helps you straighten your knee. If the tendon is ruptured, you might have trouble straightening your leg, walking, running, or jumping. Non-surgical treatment may be possible for partial patellar tendon tears. It typically includes rest, a locked hinged knee brace to keep the knee straight, physical therapy to restore strength and motion, and sometimes shock wave therapy to support healing. If the tendon is completely ruptured, surgery is usually required to restore knee function. Surgical treatment involves reattaching the tendon to the kneecap with sutures or anchors, and in chronic cases, reconstruction using a tendon graft or biologic patch to help rebuild and strengthen the repair.

PCL Tears

The knee joint is made up of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). Inside the knee, there are two important ligaments that cross each other forming an Xin the center of the knee called the notch. These two ligaments are the Posterior Cruciate Ligament (PCL) and the Anterior Cruciate Ligament (ACL). The PCL is located at the back of the knee, while the ACL is at the front. Both of these ligaments are important in providing the knee with stability. Most Grade 1 and 2 PCL injuries can heal without surgery using conservative care. Treatment focuses on rest, ice, compression, pain relief, and a structured physical therapy program that strengthens the quadriceps while avoiding strain on the ligament. A PCL-specific brace and proprioceptive training are often used to improve knee stability and control during recovery. Surgery for a PCL injury might be needed if you have multiple ligament injuries and/or you continue to have symptoms.

Posterolateral Corner (PLC) Tears

The posterolateral corner of the knee is an important area that plays a pivotal role in stability. It includes three main structures, the LCL (Lateral Collateral Ligament), the Popliteus Tendon, and the Popliteofibular Ligament. Together, these structures stabilize the outside of your knee. Injuries to the PLC can make the outside of the knee gap open and increase the tibia’s outward rotation. In most cases, PLC injuries don’t heal on their own. Additionally, PLC injuries often happen along with injuries to other knee ligaments and are more commonly injured in higher energy injuries. If these injuries are part of a multi-ligament knee injury (MLKI) , surgery is usually the best option to recreate the natural knee stability. For a complete tear of the LCL or other structures in the PLC, surgery is often needed within the first two weeks after the injury. This is the best time for surgery, particularly if we are attempting a repair, but do not think there isn’t an option if your injury was a long time ago. We can also reconstruct the PLC for more chronic injuries. New surgery techniques have improved the chances of returning to high-level activities and sports, something that was not always possible in the past.

Posteromedial Corner (PMC) Tears

The posteromedial corner of the knee includes two key structures, the MCL (Medial Collateral Ligament) and the POL (Posterior Oblique Ligament). These structures work together to keep the knee stable and prevent it from buckling or gapping open on the inside. The MCL is more active when the knee is slightly bent, while the POL works when the knee is almost straight. Most MCL injuries are mild and heal without surgery because the ligament has a strong blood supply. Treatment typically includes rest, activity modification, anti-inflammatory medications, a hinged knee brace, and physical therapy to restore strength and mobility. Surgery is considered for more severe injuries, such as significant instability or when the ligament pulls away from the tibia and cannot heal properly. Surgical options include MCL repair with augmentation or full reconstruction using grafts, often performed early to improve recovery and return to activity.

Quadriceps Tendon Tears

The quadriceps tendon is a strong, thick band of tissue that connects the quadriceps muscle (at the front of the thigh) to the top of the kneecap (patella). It helps to straighten the knee, which is essential for activities like standing, walking, running, and jumping. A quadriceps tendon rupture occurs when the quadriceps tendon tears off or near the top of the kneecap, either completely or partially. This injury affects the tendon that helps you straighten your knee. Partial quadriceps tendon tears may be treated without surgery using rest, a locked knee brace, physical therapy, and sometimes shock wave therapy to support healing. However, if the tendon is completely ruptured or the patient cannot actively straighten the leg, surgery is typically required. Surgical treatment involves reattaching the torn tendon to the kneecap using sutures or anchors. In chronic cases, reconstruction with a tendon graft or biologic patch may be used to restore strength and function.

Fellowship-Trained Orthopedic Surgeon in Los Angeles

Dr. Nima Mehran is an internationally recognized orthopedic surgeon, acclaimed researcher, and award-winning educator with specialized expertise in complex knee and shoulder surgeries. Known for his precision, innovative techniques, and compassionate care, Dr. Mehran is the trusted choice for athletes, patients, and fellow physicians seeking the highest standard of orthopedic treatment. Dr. Mehran has provided orthopedic care for elite athletes, serving on the medical staff of the Los Angeles Lakers, Los Angeles Dodgers, Los Angeles Kings, Anaheim Ducks, and USC Football team. Dr. Mehran’s commitment to excellence makes him one of the leading orthopedic surgeons in the world today.

Board-Certified Orthopedic Surgeon in Los Angeles

Dr. Matthew T. Muffly is a highly skilled and compassionate orthopaedic surgeon dedicated to providing exceptional care to his patients. With over a decade of experience in orthopedic surgery and academic medicine, Dr. Muffly specializes in advanced treatments for knee and shoulder conditions, helping patients regain mobility, reduce pain, and improve their quality of life. He is an Assistant Clinical Professor of Orthopaedic Surgery at UCLA David Geffen School of Medicine and was previously the Assistant Program Director for Resident Education at Harbor-UCLA Medical Center Department of Orthopaedic Surgery Residency Program. If you’re seeking world-class orthopedic care with a personal touch, Dr. Muffly is the trusted expert to guide you on your journey to recovery.

Expert Knee Surgery in Los Angeles

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