Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Sprains and Strains, Knee


Medical Codes

ICD-9-CM:
844.0 - Sprains and Strains of Knee and Leg, Lateral Collateral Ligament of Knee
844.1 - Sprains and Strains of Knee and Leg, Medial Collateral Ligament of Knee
844.2 - Sprains and Strains of Knee and Leg, Cruciate Ligament of Knee
844.3 - Sprains and Strains of Knee and Leg, Tibiofibular (Joint) (Ligament), Superior
844.9 - Sprains and Strains of Knee and Leg, Unspecified Site; Knee NOS; Leg NOS

Related Terms

  • ACL Tear
  • LCL Tear
  • MCL Tear
  • PCL Tear
  • Sprained Knee

Overview

The knee is a weight-bearing joint and is supported by a system of ligaments, cartilages (medial and lateral menisci), muscles, and bone structure. A ligament connects a bone to a bone. A tendon attaches a muscle to a bone. A knee sprain is damage or tearing of ligaments or the joint capsule. A knee strain refers to damage or tearing of a muscle tendon unit associated with the knee joint.

In the knee, both sprains and strains are evaluated according to the amount of looseness (laxity or instability) and loss of function that they cause. A first-degree (or grade I) injury stretches the ligament or muscle tendon unit, but does not cause significant structural damage. First-degree sprains are characterized by minimal swelling (edema), localized pain and tenderness, no instability and a good "end point" or limit to ligament stretch on exam. The individual with a first-degree sprain may perform activities within the limits of pain tolerance without causing further damage to the knee; however, activities that have high risk or reinjury (tackle football) are restricted, as the ligament does not regain normal strength for 3-6 weeks. First degree sprains occasionally have associated injury to other structures, like the menisci.

A second-degree injury partially disrupts and weakens the ligament or muscle tendon unit. Second-degree sprains are characterized by partial tears, moderately localized pain and tenderness, and mild instability. Again an "end point" is present, as at least some of the ligament is intact. The injured structure must be protected from stress for a period of about 6 weeks in order to prevent further injury. Second degree sprains more commonly have associated injury to other knee structures.

A third-degree injury is one in which the ligament or muscle tendon unit is completely disrupted. Third-degree sprains exhibit complete tears, mild to pronounced edema, and clear instability. On physical exam stress the examiner notes "no end point" unless pain induced muscle spasm limits the examiner's ability to demonstrate instability. Third degree damage requires a long period of protection from stress and often surgical repair or reconstruction. Third degree sprains frequently have associated injury to other knee structures.

Sprains can occur in any or all of the four major knee ligaments, and to other knee stabilizing ligaments. The lateral collateral ligament (LCL) is found on the outer side of each knee and attaches the thigh bone (femur) to the outside bone of the lower leg (fibula). The medial collateral ligament (MCL) is found on the inner side of each knee and attaches the femur to the shinbone (tibia). The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are both found in the middle of the knee joint itself (intra-articular) and also connect the femur to the tibia, helping to stabilize the knee joint. The MCL is the ligament most commonly injured, but damage to the ACL is the most common source of joint instability (Levy).

Sprains can occur in isolated or multiple ligaments. Sometimes other knee structures are injured in association with sprains, as in the famous "terrible triad" ("unhappy triad") of O'Donoghue, in which the ACL, MCL, and medial meniscus are all damaged. Strains are often associated with sprains and share the same risk factors and mechanisms of injury.
The knee is the most commonly injured joint in the body, with most injuries involving ligaments. Most sprains and strains result from sports activities, especially soccer, football, basketball, and skiing. Knee injuries also occur in automobile crashes.

Incidence and Prevalence: Trauma to the knee is the second most common occupational accident in the US, where knee injuries in general affect over 3 million Americans annually (Levy).

Source: Medical Disability Advisor



Diagnosis

History: The individual will most often relate a traumatic event. Sometimes the incident will have seemed insignificant at the time of occurrence, like twisting on the knee when getting up from a kneeling or squatting position. The mechanism of injury will provide valuable clues to the direction of impact and amount of force to the knee, as will information about the timing of onset of pain and swelling; immediate swelling (usually due to hemorrhage) is most often associated with acute ligament tears. Isolated meniscal tears usually do not show swelling (joint effusion) until 12-24 hours after injury. Individuals usually relate a history of pain. Individuals also may complain of the knee "giving way." Many individuals with ACL sprain report a "popping" sound in the knee. Any history of prior knee injury and treatment will be noted.

Physical exam: The examiner may touch (palpate) ligament and tendon insertion areas to elicit pain in any affected structures. Areas of localized swelling (edema) also may be felt on palpation. The joint itself may be filled with blood from the injury or with reactive synovial fluid (effusion). Pain along the course or attachment to bone (insertion) of a tendon usually indicates a strain, although strains usually occur at the muscle-tendon junction, and not at the tendon origin or insertion on bone. Pain on palpation in a ligament area often indicates a sprain. Instability or excessive motion of the knee joint often is noted, although sometimes compensatory contraction of the surrounding muscles (physiologic splinting) may prevent detection of this loosening or instability. The individual may walk with a noticeable limp, as well as a "giving way" of the knee. Edema and bruising (ecchymosis) about the knee joint may be visible. The uninjured (contralateral) leg may be compared with the injured one to detect any relevant anatomical differences, such as the position of the kneecap (patella), and to determine a baseline level of normal laxity.

Tests: Routine knee x-rays rule out fractures, dislocations, patella-femoral abnormalities, and loose bodies. Stress x-rays may be done. MRI may be ordered to examine the ligaments and articular surfaces. Physical exam is generally done to quantify the degree of laxity from ligament injury, and MRI is done to confirm the injury. MRI is especially useful in detecting accompanying (concomitant) injury, as well as in examining the severity of ligament damage. MRI also can detect bone bruises (microfractures and resulting edema in the bone from shearing or compression injury at the time the ligament tore) that may not be evident on routine x-rays. Draining fluid from the knee (joint aspiration) may be done to decrease pain and evaluate the fluid. Blood in the fluid (aspirant) indicates a torn ligament or an intraarticular fracture; fat in the bloody fluid indicates a probable intra-articular fracture. Examination of the interior of the knee with an arthroscope (surgery) may be necessary to confirm a diagnosis, as even MRI will miss significant meniscal or articular cartilage injury occasionally.

Source: Medical Disability Advisor



Treatment

First-degree sprains and strains are treated conservatively with rest from the offending activity to avoid additional injury in the next few weeks. Ice, nonsteroidal anti-inflammatory drugs (NSAIDs), light knee wraps, and muscle strengthening exercises may be included in conservative treatment.

Second-degree sprains or strains are often treated with braces that restrict but do not eliminate knee motion. Physical therapy modalities to decrease pain and exercises to strengthen muscles, and restore balance and agility are an integral part of the treatment.

Third-degree sprains may require surgical intervention for repair or reconstruction of the torn tissue. The decision to repair or reconstruct a ligament is based on the amount of instability, likelihood of increased injury without repair, number of ligaments injured, and any associated injuries.

Isolated MCL and LCL sprains usually are treated nonsurgically. If the ACL is injured, it is often treated surgically in younger and athletic individuals and non-operatively with bracing in older or sedentary individuals. See Anterior Cruciate Ligament Repair.

Few cases of PCL injury require surgery, with all first-degree and most second-degree sprains treated conservatively (Canale). Typically, surgery is not recommended for individuals older than age 50 or those with severe osteoarthritis (Peccin). When surgery is necessary for a ruptured PCL, it may involve anchoring it to bone (ligament-to-bone fixation), or reconstructing the ligament. These procedures are often performed arthroscopically.

Severe strains resulting in torn tendons are rare, but usually require surgical repair. This surgery involves suturing of the tendon ends back together (tenoplasty) or anchoring the tendon to bone (tenodesis).

Chronic instability due to rupture of tendons or ligaments is surgically repaired with procedures known as reconstruction or reconstruction with augmentation, which reinforces the unstable area with a fascia graft or transferred tendon. There are many such procedures, depending on which ligaments are non-functional.

Source: Medical Disability Advisor



Prognosis

Isolated injuries to the collateral ligaments, even third-degree injuries, generally heal well with non-operative treatment. Third-degree collateral ligament sprains associated with other ligament or meniscus damage often require surgery, but generally will heal well. Recovery can be expected when first and second-degree sprains of ACL and PCL are treated with physical therapy and activity alteration. Second degree cruciate sprains may be “protected” with a brace for instability to be worn during heavy activity that risks reinjury. Third-degree sprains of ACL that are surgically repaired, with either primary repair or reconstruction with augmentation, require an extensive rehabilitation after surgery, but recovery can be expected. Surgery to treat third-degree injuries to PCL is rarely performed on middle-aged or older adults unless there is gross instability or associated injuries, especially of the meniscus. Individuals undergoing this surgery require an extensive rehabilitation afterwards, but recovery can be expected.

Full recovery from strains can be expected after physical therapy for first and second-degree injuries. Third-degree strains and sprains will require several months for full recovery. Return to limited activity may be expected early in treatment, with an interruption for surgery and eventual return to full activity. Knee braces are often used for all levels of sprains and strains, sometimes only in the early stages of recovery, and often for several months after surgery. Protective braces may be required after recovery to prevent re-injury.

Source: Medical Disability Advisor



Differential Diagnosis

Source: Medical Disability Advisor



Specialists

  • Orthopedic (Orthopaedic) Surgeon
  • Physiatrist (Physical Medicine and Rehabilitation Specialist)
  • Physical Therapist
  • Sports Medicine Physician

Source: Medical Disability Advisor



Rehabilitation

The initial goal of rehabilitation is to reduce pain and swelling. Controlling the pain and swelling associated with the acute phase of injury begins with PRICE (protection, rest, ice, compression, elevation) for the first 48 hours after injury or until swelling has stabilized (Braddom). Once the acute phase has subsided, current clinical practice supports the use of other modalities, heat or electrical stimulation, as means to promote pain control and allow for active rehabilitation.

For sprains and strains of the knee, a short period of immobilization and protection with a brace or semi-rigid support may be advised. Once the acute swelling and pain have subsided, individuals can be started on a rehabilitation program that will focus on functional training, with the intensity based upon the degree of soft tissue injury, in order to improve activities of daily living. Stretching exercises to promote full range of motion should be started as soon as possible. The treatment program will progress to strengthening and proprioceptive exercises as tolerated. No particular exercise regime has proved superior for anterior cruciate injures (Trees) nor have knee braces been shown to improve outcomes (Swirtun).

The final goal of therapy is to restore the individual's full pre-injury functional status. A home exercise program should be taught to complement supervised rehabilitation and to be continued as indicated, even after discharge from therapy.

If surgery becomes necessary, the rehabilitation protocol will be guided by the treating physician. Additional information may provide greater insight into the rehabilitation needs for managing this condition (Biundo).

FREQUENCY OF REHABILITATION VISITS
Nonsurgical
SpecialistSprains and Strains, Knee
Physical TherapistUp to 16 visits within 8 weeks
Surgical
SpecialistSprains and Strains, Knee
Physical TherapistUp to 24 visits within 12 weeks
Note on Surgical Guidelines: This table reflects the average rehabilitation needs. The degree of injury and surgical procedure can greatly impact on the duration of rehabilitation, and a longer period of rehabilitation may be required than that reflected in the table.
The table above represents a range of the usual acceptable number of visits for uncomplicated cases. It provides a framework based on the duration of tissue healing time and standard clinical practice.

Source: Medical Disability Advisor



Comorbid Conditions

Source: Medical Disability Advisor



Complications

Recurrent accumulations of fluid (effusions), osteoarthritis, buckling episodes (“giving way”) with loss of function, or any abnormal knee movement may complicate treatment and recovery.

Source: Medical Disability Advisor



Factors Influencing Duration

Duration will depend on the extent of the injury, type of therapy used, effectiveness of treatment, presence of concomitant injuries, complications, age, co-morbidities (injuries to other parts of the limb, injuries to the other lower limb, systemic disease), and job requirements.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

During conservative treatment, walking, climbing, squatting, or kneeling during early treatment stages is restricted. This restriction may necessitate use of braces, crutches, canes, or wheelchairs. If crutches, canes, or wheelchairs are needed, relocation to an accessible area of the workplace may be required, along with additional safety precautions. Individuals will need frequent rest periods that allow for elevation of the lower leg. Company policy on medication usage should be reviewed to determine if pain medication use is compatible with job safety and function. Individuals whose injuries do not require surgical repair or reconstruction may nonetheless need time off from work to undergo extensive physical therapy to regain function.

During the recovery phase following surgery, avoidance of squatting, crawling, or kneeling for several months, along with use of a protective brace, may be necessary. Other activities to be avoided include jumping, twisting, lifting, pushing, or lunging. Avoidance of these activities is often facilitated by use of a protective brace to prevent re-injury. Additional time off for extensive physical therapy may be needed.

For more information, refer to “Ability to Work,” pages 234-241.

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Has diagnosis been confirmed by MRI and / or surgery?
  • If individual has continued pain or stiffness after treatment, was an MRI done to search for a missed injury?
  • Does either MRI or arthroscopy show injury to the articular cartilage of the knee?
  • Is a “bone bruise” present on MRI? (These may produce knee pain for up to 6-8 months, but resolve with time.)
  • If imaging results were equivocal, would diagnostic arthroscopy be appropriate?

Regarding treatment:

  • Has individual been prescribed a custom fit brace that protects the injured ligament?
  • Has individual been enrolled in a comprehensive rehabilitation program that includes physical therapy to strengthen muscles, and restore balance and agility as an integral part of the treatment? If muscle atrophy or knee limitation of motion is still present, is additional physical therapy indicated?
  • Is surgical intervention warranted and on what basis?
  • Has individual experienced any complications such as infection, recurrent effusions, osteoarthritis, loss of knee motion, or chronic instability with loss of function?

Regarding prognosis:

  • Is individual middle-aged or older? Many older individuals with residual instability or arthritis never regain their pre-injury status.
  • Does individual have an injury to a meniscus and residual instability (this combination predicts an increased risk of post-traumatic arthritis)?
  • Have temporary workplace accommodations been made to allow for surgery and resultant rehabilitation period? Is a permanent change to easier work likely to result in return to work?

Source: Medical Disability Advisor



References

Cited

Biundo, J. J., R. W. Irwin, and E. Umpierre. "Sports and Other Soft Tissue Injuries, Tendinitis, Bursitis, and Occupation-Related Syndromes." Current Opinion in Rheumatology 13 2 (2001): 146-149. National Center for Biotechnology Information. National Library of Medicine. 22 Jan. 2009 <PMID: 11224739>.

Braddom, Randolph L. Physical Medicine and Rehabilitation. 3rd ed. Philadelphia: W.B. Saunders, 2006.

Levy, David, et al. "Knee Injury, Soft Tissue." eMedicine. Eds. Eric Kardon, et al. 27 Feb. 2013. Medscape. 20 Mar. 2013 <http://emedicine.medscape.com/article/826792-overview>.

Peccin, M., et al. "Interventions for treating posterior cruciate ligament injuries of the knee in adults." Cochrane Database of Systematic Reviews 2 (2005): NA.

Swirtun, L., A. Jansson, and P. Renstrom. "The effects of a functional knee brace during early treatment of patients with a nonoperated acute anterior cruciate ligament tear: A prospective randomized study." Clinical Journal of Sports Medicine 15 5 299-304.

Talmage, J. B. , J. M. Melhorn, and M. H. Hyman, eds. Work Ability and Return to Work, AMA Guides to the Evaluation of. Second ed. Chicago: AMA Press, 2011.

Trees, A., et al. "Exercise for treating anterior cruciate ligament injuries in combination with collateral ligament and meniscal damage of the knee in adults." Cochrane Database of Systematic Reviews 3 (2007): NA.

Source: Medical Disability Advisor