Attenuated patella alta is an extremely rare condition affecting mobility and leg strength. It is characterized by an unusually small knee cap (patella) that develops out of and above the joint. Normally, as the knee cap sits in the joint, it is stimulated to growth by abrasion from the opposing bones. When not situated properly in the joint, the knee cap does not experience such stimulation and remains small and undeveloped. Note that the cartilage under and around the kneecap is eight times smoother than ice, so "abrasion" may not be the best term.

A similar condition, patella alta, can occur as the result of a sports injury, though the large majority of the time it is a congenital/developmental condition that is unrelated to trauma. A kneecap in an "alta" position sits above the "trochlear groove" and therefore is less stable. The "patellar tendon" that connects the kneecap to the tibia (shinbone)is elongated (longer than normal). This cannot happen by way of trauma, unless there has been a rupture of the tendon and a less-than-optimal surgical repair.

There has been only one documented case of the disorder noted from birth. In 1988, three-year-old Eric Rogstad of Minneapolis, Minnesota was discovered to suffer from the condition in both knees after several attempts by his parents and family physician to discover the cause of his abnormal difficulties with walking and running. After surgery and physical therapy, Eric gained the ability to walk and run without significant difficulty.

Insall Ratio: This ratio is calculated with the knee flexed to 30 degrees. It is the ratio of the length of the patella to the length of the patellar tendon. Normally this ratio is 1:1 but 20% variation represents patella alta or patella infera. Actually, the Insall-Salvati ratio can be measured at any degree of flexion, which is one reason for its popularity.

Plica syndrome treatment focuses on decreasing inflammation of the synovial capsule. A nonsteroidal anti-inflammatory drug (NSAID) is often used in conjunction with therapeutic exercise and modalities. Iontophoresis and phonophoresis have been utilized successfully against inflammation of the plica and synovial capsule. Failing these, surgical removal of the plica of the affected knee may be necessary.

Treatment may be with or without surgery, depending on the type of fracture.

OCD is a relatively rare disorder, with an estimated incidence of 15 to 30 cases per 100,000 persons per year. Widuchowski W "et al." found OCD to be the cause of articular cartilage defects in 2% of cases in a study of 25,124 knee arthroscopies. Although rare, OCD is noted as an important cause of joint pain in active adolescents. The juvenile form of the disease occurs in children with open growth plates, usually between the ages 5 and 15 years and occurs more commonly in males than females, with a ratio between 2:1 and 3:1. However, OCD has become more common among adolescent females as they become more active in sports. The adult form, which occurs in those who have reached skeletal maturity, is most commonly found in people 16 to 50 years old.

While OCD may affect any joint, the knee—specifically the medial femoral condyle in 75–85% of knee cases—tends to be the most commonly affected, and constitutes 75% of all cases. The elbow (specifically the capitulum of the humerus) is the second most affected joint with 6% of cases; the talar dome of the ankle represents 4% of cases. Less frequent locations include the patella, vertebrae, the femoral head, and the glenoid of the scapula.

OCD also is found in animals, and is of particular concern in horses, as there may be a hereditary component in some horse breeds. Feeding for forced growth and selective breeding for increased size are also factors. OCD has also been studied in other animals—mainly dogs, especially the German Shepherd—where it is a common primary cause of elbow dysplasia in medium-large breeds.

In animals, OCD is considered a developmental and metabolic disorder related to cartilage growth and endochondral ossification. Osteochondritis itself signifies the disturbance of the usual growth process of cartilage, and OCD is the term used when this affects joint cartilage causing a fragment to become loose.

According to the Columbia Animal Hospital the frequency of affected animals is dogs, humans, pigs, horses, cattle, chickens, and turkeys, and in dogs the most commonly affected breeds include the German Shepherd, Golden and Labrador Retriever, Rottweiler, Great Dane, Bernese Mountain Dog, and Saint Bernard. Although any joint may be affected, those commonly affected by OCD in the dog are: shoulder (often bilaterally), elbow, knee and tarsus.

The problem develops in puppyhood although often subclinically, and there may be pain or stiffness, discomfort on extension, or other compensating characteristics. Diagnosis generally depends on X-rays, arthroscopy, or MRI scans. While cases of OCD of the stifle go undetected and heal spontaneously, others are exhibited in acute lameness. Surgery is recommended once the animal has been deemed lame.

Osteochondritis dissecans is difficult to diagnose clinically as the animal may only exhibit an unusual gait. Consequently, OCD may be masked by, or misdiagnosed as, other skeletal and joint conditions such as hip dysplasia.

Undisplaced fracture can usually be treated by casting. Even some displaced fractures can be treated with casting as long as a person can straighten their leg without help. Typically the leg is immobilized in a straight position for the first three weeks and then increasing degrees of bending are allowed.

An effective rehabilitation program reduces the chances of reinjury and of other knee-related problems such as patellofemoral pain syndrome and osteoarthritis. Rehabilitation focuses on maintaining strength and range of motion to reduce pain and maintain the health of the muscles and tissues around the knee joint.

In the absence of cartilage damage, pain at the front of the knee due to overuse can be managed with a combination of RICE (rest, ice, compression, elevation), anti-inflammatory medications, and physiotherapy.

Usually chondromalacia develops without swelling or bruising and most individuals benefit from rest and adherence to an appropriate physical therapy program. Allowing inflammation to subside while avoiding irritating activities for several weeks is followed by a gradual resumption. Cross-training activities such as swimming, strokes other than the breaststroke, can help to maintain general fitness and body composition. This is beneficial until a physical therapy program emphasizing strengthening and flexibility of the hip and thigh muscles can be undertaken. Use of nonsteroidal anti-inflammatory medication is also helpful to minimize the swelling amplifying patellar pain. Treatment with surgery is declining in popularity due to positive non-surgical outcomes and the relative ineffectiveness of surgical intervention.

Two types of treatment options are typically available:

- Surgery

- Conservative treatment (rehabilitation and physical therapy)

Surgery may impede normal growth of structures in the knee, so doctors generally do not recommend knee operations for young people who are still growing. There are also risks of complications, such as an adverse reaction to anesthesia or an infection.

When designing a rehabilitation program, clinicians consider associated injuries such as chipped bones or soft tissue tears. Clinicians take into account the person's age, activity level, and time needed to return to work and/or athletics. Doctors generally only recommend surgery when other structures in the knee have sustained severe damage, or specifically when there is:

- Concurrent osteochondral injury

- Continued gross instability

- Palpable disruption of the medial patellofemoral ligament and the vastus medialis obliquus

- High-level athletic demands coupled with mechanical risk factors and an initial injury mechanism not related to contact

Supplements like glucosamine and NSAIDs can be used to minimize bothersome symptoms.

Steroid injections are helpful in the short term (first approximately 4 weeks) however, their long term effectiveness is not known, and quality of evidence for its use remains poor and controversial.

Other, more conservative and non-surgical, treatment options available for the management and treatment of tendinopathy include: rest, ice, massage therapy, eccentric exercise, NSAIDs, ultrasound therapy, LIPUS, electrotherapy, taping, sclerosing injections, blood injection, glyceryl trinitrate patches, and (ESWT) extracorporeal shockwave therapy. Studies with a rat model of fatigue-damaged tendons suggested that delaying exercise until after the initial inflammatory stage of repair could promote remodelling more rapidly. There is insufficient evidence on the routine use of injection therapies (Autologous blood, Platelet-rich plasma, Deproteinised haemodialysate, Aprotinin, Polysulphated glycosaminoglycan, Corticosteroid, Skin derived fibroblasts etc.) for treating Achilles tendinopathy. As of 2014 there was insufficient evidence to support the use of platelet-rich therapies for treating musculoskeletal soft tissue injuries such as ligament, muscle and tendon tears and tendinopathies.

A Cochrane review of low-intensity pulsed ultrasound to speed healing in newly broken bones found insufficient evidence to justify routine use. Other reviews have found tentative evidence of benefit. It may be an alternative to surgery for established nonunions.

Vitamin D supplements combined with additional calcium marginally reduces the risk of hip fractures and other types of fracture in older adults; however, vitamin D supplementation alone did not reduce the risk of fractures.

Persons with knock knees often have collapsed inner arches of their feet, and their inner ankle bones are generally lower than their outer ankle bones. Adults with uncorrected genu valgum are typically prone to injury and chronic knee problems such as chondromalacia and osteoarthritis. These in turn can cause severe pain and problems in walking.

It is normal for children to have knock knees between the ages of two and five years of age, and almost all of them resolve as the child grows older. If symptoms are prolonged and pronounced or hereditary, doctors often use orthotic shoes or leg braces at night to gently move a child's leg back into position. If the condition persists and worsens later in life, surgery may be required to relieve pain and complications resulting from severe or hereditary genu valgum. Available surgical procedures include adjustments to the lower femur and total knee replacement (TKR).

Weight loss and substitution of high-impact for low-impact exercise can help slow progression of the condition. With every step, the patient's weight places a distortion on the knee toward a knocked knee position, and the effect is increased with increased angle or increased weight. Even in the normal knee position, the femurs function at an angle because they connect to the hip girdle at points much further apart than they connect at the knees.

Physical therapy is generally of benefit to people with knock knees. To correct knock knees, the entire leg must be treated, especially:

1. Activating and developing the arches of the feet,

2. Waking up the outer leg muscles (abductors), and

3. Learning how to move the inner ankle bone inwards towards the outer ankle bone, and upwards towards the knee.

Working with a physical medicine specialist such as a physiatrist, or a physiotherapist may assist a patient learning how to improve outcomes and use the leg muscles properly to support the bone structures. Alternative or complementary treatments may include certain procedures from Iyengar Yoga or the Feldenkrais Method.

Rarely, the bone malformation underlying knock knees can be traced to a lack of nutrition necessary for bone growth, which can cause conditions such as rickets (lack of bone nutrients, especially dietary vitamin D and calcium), or scurvy (lack of vitamin C). The correction of the underlying vitamin deficiency may restore a more normal progression of bone growth.

Bipartite patella is a condition where the patella, or kneecap, is composed of two separate bones. Instead of fusing together as normally occurs in early childhood, the bones of the patella remain separated. The condition occurs in approximately 12% of the population and is nine times more likely to occur in males than females. It is often asymptomatic and most commonly diagnosed as an incidental finding, with about 2% of cases becoming symptomatic.

In children, whose bones are still developing, there are risks of either a growth plate injury or a greenstick fracture.

- A greenstick fracture occurs due to mechanical failure on the tension side. That is, since the bone is not so brittle as it would be in an adult, it does not completely fracture, but rather exhibits bowing without complete disruption of the bone's cortex in the surface opposite the applied force.

- Growth plate injuries, as in Salter-Harris fractures, require careful treatment and accurate reduction to make sure that the bone continues to grow normally.

- Plastic deformation of the bone, in which the bone permanently bends, but does not break, also is possible in children. These injuries may require an osteotomy (bone cut) to realign the bone if it is fixed and cannot be realigned by closed methods.

- Certain fractures mainly occur in children, including fracture of the clavicle and supracondylar fracture of the humerus.

Specific populations at high risk of primary PFPS include runners, bicyclists, basketball players, young athletes and females.

While genu valgum is often a symptom of genetic disorders it can be caused by poor nutrition. A major contributor to genu valgum is obesity, and far less commonly calcium and vitamin d deficiencies.

Arthrofibrosis of the knee has been one of the more studied joints as a result of its frequency of occurrence. Beyond origins such as knee injury and trauma, arthrofibrosis of the knee has been associated with degenerative arthritis. Scar tissues can cause structures of the knee to become contracted, restricting normal motion. Depending on the site of scarring, knee cap mobility and/or joint range of motion (i.e. flexion, extension, or both) may be affected. Symptoms experienced as a result of arthrofibrosis of the knee include stiffness, pain, limping, heat, swelling, crepitus, and/or weakness. Clinical diagnosis may also include the use of magnetic resonance imaging (or MRI) to visualize the knee compartments affected.

The consequent pain may lead to the cascade of quadriceps weakness, patellar tendon adaptive shortening and scarring in the tissues around the knee cap—with an end stage of permanent patella infera—where the knee cap is pulled down into an abnormal position where it becomes vulnerable to joint surface damage.

Patients who are recognized as developing arthrofibrosis may improve motion with appropriately directed physical therapy, corticosteroid injections, non-steroidal anti-inflammatory drugs, and cryotherapy. In many instances, however, as fibrosis has set in, surgical intervention is necessary. Specialized arthroscopic lysis of adhesions knee procedures such as anterior interval releases may be indicated and utilized to great success, in the hands of an appropriately trained specialist.

Increase bone density

Spool vertebrae

Obtuse angle of mandible

Acroosteolysis

Melorheostosis

Candle dripping sign

Nail patella syndrome

Thanatophoric dwarfism

Future research with regard to medial knee injuries should evaluate clinical outcomes between different reconstruction techniques. Determining the advantages and disadvantages of these techniques would also be beneficial for optimizing treatment.

In the United States, more than US $3 billion is spent each year on arthroscopic knee surgeries that are known to be ineffective in people with degenerative knee pain.

Low arches can cause overpronation or the feet to roll inward too much increasing the Q angle and genu valgum. Poor lower extremity biomechanics may cause stress on the knees and ultimately patellofemoral pain syndrome. Stability or motion control shoes are designed for people with pronation issues. Arch supports and custom orthotics may also help to improve lower extremity biomechanics.

The condition is usually self-limiting and is caused by stress on the patellar tendon that attaches the quadriceps muscle at the front of the thigh to the tibial tuberosity. Following an adolescent growth spurt, repeated stress from contraction of the quadriceps is transmitted through the patellar tendon to the immature tibial tuberosity. This can cause multiple subacute avulsion fractures along with inflammation of the tendon, leading to excess bone growth in the tuberosity and producing a visible lump which can be very painful, especially when hit. Activities such as kneeling may also irritate the tendon.

The syndrome may develop without trauma or other apparent cause; however, some studies report up to 50% of patients relate a history of precipitating trauma. Several authors have tried to identify the actual underlying etiology and risk factors that predispose Osgood–Schlatter disease and postulated various theories. However, currently it is widely accepted that Osgood–Schlatter disease is a traction apophysitis of the proximal tibial tubercle at the insertion of the patellar tendon caused by repetitive micro-trauma. In other

words, Osgood–Schlatter disease is an overuse injury and closely related to the physical activity of the child. It was shown that children

who actively participate in sports are affected more frequently as compared with non-participants. In a retrospective study of adolescents, old athletes actively participating in sports showed a frequency of 21% reporting the syndrome compared with only 4.5% of age-matched nonathletic controls.

The symptoms usually resolve with treatment but may recur for 12–24 months before complete resolution at skeletal maturity, when the tibial epiphysis fuses. In some cases the symptoms do not resolve until the patient is fully grown. In approximately 10% of patients the symptoms continue unabated into adulthood, despite all conservative measures.

About 25% of people over the age of 50 experience knee pain from degenerative knee diseases.

Tendon injury and resulting tendinopathy are responsible for up to 30% of consultations to sports doctors and other musculoskeletal health providers. Tendinopathy is most often seen in tendons of athletes either before or after an injury but is becoming more common in non-athletes and sedentary populations. For example, the majority of patients with Achilles tendinopathy in a general population-based study did not associate their condition with a sporting activity. In another study the population incidence of Achilles tendinopathy increased sixfold from 1979-1986 to 1987-1994. The incidence of rotator cuff tendinopathy ranges from 0.3% to 5.5% and annual prevalence from 0.5% to 7.4%.

It is possible to prevent the onset of prepatellar bursitis, or prevent the symptoms from worsening, by avoiding trauma to the knee or frequent kneeling. Protective knee pads can also help prevent prepatellar bursitis for those whose professions require frequent kneeling and for athletes who play contact sports, such as American football, basketball, and wrestling.