The anterior cruciate ligament (ACL), situated in the middle of the knee joint, runs diagonally to keep the tibia and femur aligned as well as to provide rotational stability. Athletes in high-intensity sports like soccer, football and basketball are at high risk for ACL injuries. These are graded on a scale from 1 (mild damage) to 3 (complete tear).
- Direct contact or collision
- Changing direction rapidly
- Stopping suddenly
- Landing from a jump incorrectly
- Pain and swelling within 24 hours of the injury
- Limited range of motion
- Tenderness along the joint line
- Discomfort while walking
Treatment of an ACL tear depends on the patient: young athletes hoping to return to their sports will likely require surgery, while older patients may find relief through nonsurgical options such as activity modification, bracing and physical therapy. To repair the ACL, the surgeon must replace the torn ligament with a tissue graft, which acts as a scaffolding for the growth of new tissue. This can usually be done arthroscopically, involving a few small incisions.
Three types of arthritis may affect the knee joint: osteoarthritis, rheumatoid arthritis (RA) and post-traumatic arthritis that can develop after an injury.
- Pain and stiffness that comes on gradually
- Pain that increases with walking, stair climbing or kneeling
- Weakness in the joint that can result in locking or buckling
Osteoarthritis of the knee can be treated with a variety of nonsurgical techniques, such as lifestyle modification, physical therapy, supportive devices and medication. If your condition does not improve with these approaches, your physician may recommend surgery; surgical approaches include arthroscopic cartilage repair, osteotomy (a surgery in which the bone is cut to shorten, lengthen, or alter its alignment) and total joint replacement.
Avascular necrosis (AVN) is a condition that develops in one of the bones of the knee joint as a result of reduced blood flow to the bone. This lack of blood can cause bone cells to die, resulting in severe pain and possibly a collapse of the bone structure.
The exact cause of avascular necrosis is still being researched; some risk factors for developing the disease include:
- Heavy alcohol use
- Long-term steroid use
- Decompression sickness (also known as divers' disease or caisson disease)
Avascular necrosis causes pain and limited range of motion in one or both knees; many patients, however, experience no symptoms at all.
The goal of treatment for avascular necrosis is preventing further bone loss. This may include medication (nonsteroidal anti-inflammatory drugs or osteoporosis medications such as alendronate (Fosamax)), rest or physical therapy or surgery (core decompression, bone graft, bone resurfacing, or joint replacement).
The pes anserine bursa is a small lubricating sac between the shinbone (tibia) and three tendons of the hamstrings at the inside of the knee. Overuse of the knee or stress on the bursa can result in inflammation (bursitis). It is a common condition in athletes, particularly runners.
- Incorrect training techniques
- Tight hamstrings
- Outward turning of the knee or lower leg
- Osteoarthritis in the knee
- Medial meniscus tear
- Pain that develops slowly about 2-3 inches below the kneecap
- Pain that increases with activity such as climbing stairs
Most cases of knee bursitis can be successfully treated with rest, ice, anti-inflammatory medications and/or steroid injections.
Cartilage in the knee can become damaged as the result of a fall, a sports-related injury, a prior injury, simple wear and tear over time, or immobilization over a long period.
- Recurring pain and swelling in the knee
- "Locking" of the knee (due to loose tissue within the joint)
- Clicking or other noise with knee movement
If the damage to the cartilage is minor, the injury may heal on its own with rest, ice, anti-inflammatory medications and rehabilitation exercises. More severe injuries may require surgery to repair the damaged cartilage.
The patellar tendon connects the kneecap (patella) to the shinbone (tibia) and is part of the mechanism that allows the leg to straighten. Patellar tendonitis is a condition in which this tendon and the tissues around it become irritated and inflamed.
- Overuse of the knee, especially in "jumping sports" such as basketball and volleyball
- Acute injury to the tendon that has not healed properly
- Pain at the kneecap
- Pain that increases with activities such as jumping or kneeling
- Swelling around the tendon
Most cases of patellar tendonitis can be treated with nonsurgical approaches, including rest, ice, anti-inflammatory medications, stretching, and/or braces. In rare cases, surgery may be needed to repair the tendon.
As your knee bends, the kneecap (patella) slides up and down in a "groove" at the end of the thigh bone (femur). If an injury causes the kneecap to be pulled towards the outside of the knee, it slides outside of this groove and dislocation occurs.
- Sudden change in direction when the leg is planted
- Direct blow to the knee, as in a low tackle
- Inability to straighten the knee
- Visible dislocation of the kneecap
- Pain, tenderness, and swelling
- Hypermobile kneecap (the kneecap can be moved back and forth further than normal)
If the dislocation has not caused damage to other bones, your physician will probably place the knee in an immobilizer or cast for several weeks. After the cast somes off, you'll probably need physical therapy to restore muscle strength and range of motion. If the knee remains unstable, you may need surgery to stabilize the kneecap.
The medical collateral ligament (MCL) is one of four ligaments that are essential to the stability of the knee joint. Located on the inside of the knee joint, the MCL spans from the lower tip of the thigh bone (femur) to the top of the shin bone (tibia). The MCL prevents over-widening of the inside of the knee joint.
Most MCL injuries result from a direct blow to the outside of the knee (as in "clipping" in football), which causes the outside of the joint to buckle and the inside to widen. This causes the MCL to over-stretch, which can result in injury or tearing. Other ligaments, including the ACL or the meniscus, are sometimes torn at the same time as the MCL.
- Pain, swelling and bruising directly over the ligament
- Instability or buckling of the knee joint
Early treatment of MCL injuries involves rest, ice, anti-inflammatory medications, rehabilitation exercises and/or the use of a brace. More severe tears may require the use of crutches for several weeks until the pain subsides, followed by range-of-motion exercises. Surgery is rarely required.
On each side of the knee joint, between the thigh bone (femur) and the shin bone (tibia), there is a wedge-shaped piece of cartilage, called the meniscus, that helps cusion the joint and keep it stable. Menisci can be torn in different ways, and each type of tear is distinguished by its shape (see image at right).
- Twisting the knee in a squatting position
- Direct contact, as in a football tackle
- Wear and tear over time
A "pop" is usually felt when a meniscus is injured. You may be able to walk on the injured leg or even return to the field immediately after the injury; however, over the next few days, the knee will become painful, stiff and swollen. Other symptoms may include catching or locking of the joint, limited range of motion or a feeling that the knee is giving way.
If the tear is small and located on the outer edge of the meniscus, it may just require R.I.C.E. therapy (rest, ice, compression, elevation) and anti-inflammatory medications. If the tear is more severe or if symptoms persist, your physician may recommend arthroscopic surgery to repair the tear.
Caused by reduced blood flow to the end of a bone, osteochondritis dissecans is a condition in which a piece of cartilage, along with the thin layer of bone beneath it, becomes detached. It's most common in the knee but can sometimes occur in the elbow, shoulder, hip or ankle.
Osteochondritis dissecans in the knee is caused by a reduction in blood flow to the lower end of the thigh bone (femur), which can result from a repetitive minor injury or may be linked to certain genetic factors.
- Pain with physical activity such as climbing stairs or playing sports
- Popping or locking of the joint
- Feeling that the knee is "giving way"
- Decreased range of motion
- Swelling and tenderness
At first, your physician will recommend nonsurgical approaches such as rest and physical therapy to stretch and strengthen the joint. If symptoms persist, you may need surgery to remove or re-attach the loose fragments, which can be performed using minimally invasive arthroscopic procedures.
The patellar tendon and the quadriceps tendon are part of the mechanism that allows the knee to straighten. A fall onto a partially bent knee can cause either or both of these tendons to rupture.
When you fall onto a bent knee, the quadriceps rapidly contract to break the fall; if the patellar or quadriceps tendon is unable to withstand the force, it ruptures. This injury is most common in middle-aged athletes or part-time "weekend warriors."
- Immediate "pop" or tearing sensation at the time of injury
- Inability to straighten the leg
- Pain and swelling in the knee
- Difficulty walking due to weakness in the knee
- Sagging or drooping of the kneecap
If the tear is partial, your physician will recommend that you wear an immobilizer or brace to keep the knee straight while the tendon heals. Once the initial pain and swelling subside, you'll be able to begin physical therapy to stretch and strengthen the joint. Complete tears require surgery to repair the torn tendon.
Located at the back of the knee, the posterior cruciate ligament (PCL) is one of several ligaments that connect the thigh bone (femur) to the shin bone (tibia). PCL injuries are considered sprains and are graded on a severity scale from 1 (slightly stretched) to 3 (complete tear).
PCL injuries are usually caused by a powerful impact; examples include the knee hitting a dashboard in a car accident or hard fall onto a bent knee in sports.
- Pain and swelling immediately following the injury
- Stiffness that may cause a limp
- Instability or a feeling that the knee is "giving out"
If no other ligaments besides the PCL are injured, you may only need nonsurgical treatment, including R.I.C.E. (rest, ice, compression, elevation), use of a brace and crutches, and physical therapy. If other ligaments were injured along with the PCL, you may need surgery to repair the damage.
"Runner's knee" may refer to one of several medical conditions that can cause pain around the front of the knee. It's common among athletes whose sports place heavy stress on the knees, including running, basketball, skiing, cycling and soccer.
- Misaligned kneecap
- Excessive training or overuse
- Tightness, imbalance or weakness of thigh muscles
- Flat feet
- Dull, aching pain around the kneecap
- Pain that occurs when walking up or down stairs, kneeling, squatting, and sitting with a bent knee for long periods
Your physician will first recommend refraining from any activities that hurt the knee, especially running and jumping, R.I.C.E. therapy (rest, ice, compression, elevation), anti-inflammatory medications and/or the use of a knee brace. If the pain continues, you may need surgery to remove damaged cartilage or realign the kneecap.